# Can anyone shed some light on the differences in the various 2500 movements? B, C, D etc...



## 6SpeedTA95 (Mar 19, 2010)

If it's a link to an older thread or an article or something that would be great. Or if you know and can post them here that is great too. I thought there was a thread about that but I've searched on the forum and searched on google and can't really find anything that lines out the differences by version. Help would be appreciated...


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## mazman01 (Sep 26, 2011)

I'd like to know too. And if you don't mind, how the 8500 compares to them, and what specifically makes it better as everyone says. If not in this thread than another maybe, as to not hijack this one.


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## 6SpeedTA95 (Mar 19, 2010)

mazman01 said:


> I'd like to know too. And if you don't mind, how the 8500 compares to them, and what specifically makes it better as everyone says. If not in this thread than another maybe, as to not hijack this one.


Feel free to discuss that here. Just keep in mind theere is a 2500 vs 8500 thread already on the omega front page.


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## Mystro (Oct 26, 2008)

On a side note. the Planet Ocean only has had the 2500C movement from its introduction. It has recently received the 2500D movement. Only time will tell what if any advantages or disadvantages the 2500D movement has over the 2500C.


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## iinsic (Feb 18, 2010)

A lot was covered here: https://www.watchuseek.com/f20/will-2500d-end-reliability-issues-617533.html


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## lvt (Sep 15, 2009)

The 2500's escapement is simple, fully functional, but Omega found that they could still make a better one










The D version's escapement is almost identical to the 8500's but without the Si14 balance wheel.










It's heavily modified and more complicated than the 2500 (B, C) escapement and would be capable of running at higher beat rate in the future like the 93xx (anyway it won't happen with the 2500D).


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## M4tt (Jan 18, 2007)

Only the 2500 B, C and D are likely to be seen on WUS. The major differences between the three are: 

The B revision had a beat rate of 28,800 and wouldn't always start from rest without a flick. 

The C revision had a beat rate of 25,200 which put a little more torque into the escapement for the same strength of spring. This gave slightly lower wear, pretty well certain self starting and an extra four hours reserve for no significant loss of stability. In addition there were some minor changes to the shape of the lever, small variations in lift angle and so on. 

The D revision split the coaxial wheel from two layers to three to separate the function of taking power from the intermediate wheel from the function of providing an impulse to the pallet. In the 2500C, the pinion wheel did both jobs. In the 2500D, the job of taking power from the intermediate wheel has been delegated to an ordinary cog. This leaves the pinion wheel free to do a single job well.

The C solution is the more elegant while the D solution simplifies the problem (powering the pinion wheel) to be solved. Which is the better solution is probably a matter of taste. Personally, I have two B revisions, which makes my opinion on the matter pretty clear.

I also do not believe any version of the 2500 apart from the A to be any less reliable than any equivalent movement. My reasons have been repeated so many times as to be easily found through search and so I will not bother rehearsing them here.


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## lvt (Sep 15, 2009)

Good explanation, M4tt, as usual.

I also think that the 2500 is as reliable as a 2892 but the 2892 has a big advantage : its simplicity, and in mechanical stuffs simplicity means more reliability.










The 2500D/8500 escapement is even more complicated than the previous 2500 with added parts so I still ignore how the Co-ax would last longer than a Swiss lever which is 10 times simpler, escecially when the next generation of the Co-ax will all run in 28,800bph.

At least one thing for sure now is that the 3-tier escapement seems to have a better handling of the power flow so the stoppage and the flick-to-start could be avoided.


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## iinsic (Feb 18, 2010)

M4tt said:


> The C revision had a beat rate of 25,200 which put a little more torque into the escapement for the same strength of spring. This gave slightly lower wear, pretty well certain self starting and an extra four hours reserve for no significant loss of stability. In addition there were some minor changes to the shape of the lever, small variations in lift angle and so on.
> 
> The D revision split the coaxial wheel from two layers to three to separate the function of taking power from the intermediate wheel from the function of providing an impulse to the pallet. In the 2500C, the pinion wheel did both jobs. In the 2500D, the job of taking power from the intermediate wheel has been delegated to an ordinary cog. This leaves the pinion wheel free to do a single job well.


So how does changing the escape wheel in the repairs of nonworking 2500Cs resolve whatever underlying problem exists with the unmodified movement? What has Omega figured out about the 2500C that they think will be fixed by this switch?


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## Dixan (Oct 10, 2009)

lvt said:


> The 2500D/8500 escapement is even more complicated than the previous 2500 with added parts so I still ignore how the Co-ax would last longer than a Swiss lever which is 10 times simpler, *escecially when the next generation of the Co-ax will all run in 28,800bph.*


Dude, you have to stop putting out this bad information. Did I miss something, here? Unless something happened since the last time you made this same irresponsible, purely speculative statement, and Omega has since officially announced that the next generation of Co-Axial movements will again beat at a faster beat rate, then your statement once again comes across as nothing more than your _wish,_ stated as fact. Please stop stating things _you personally wish_ to see happen as factual, or otherwise officially planned. :roll:

EDIT: IDK, maybe word your statements in a way that conveys your desire for Omega to bring future Co-Axial movement beat rates back up, but doesn't necessarily (mis)state that that will happen for sure, or is in any way officially planned by Omega. You might not even be alone in wishing that would happen. I personally don't see it happening, but I guess we'll just have to see.


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## M4tt (Jan 18, 2007)

> I also think that the 2500 is as reliable as a 2892 but the 2892 has a big advantage : its simplicity, and in mechanical stuffs simplicity means more reliability.


So, just to be clear, you are saying that they are both as reliable but the 2892 is more reliable because it is simpler?

Personally I think that simplicity is not obviously the key reason that something is reliable. Good, well executed design in high quality materials is usually the reason that something is reliable. Take a Russian Lada car engine. These are astonishingly simple and, in my experience, often have a total of *no *moving parts. A Mercedes engine is significantly more complex and yet manages to be infinitely more reliable. Likewise, a quartz watch is a far more complex design than a mechanical (if a little more inscrutable) and yet...

As for the changes between the 2500C and the 2500D...



> The 2500D/8500 escapement is even more complicated than the previous 2500 with added parts so I still ignore how the Co-ax would last longer than a Swiss lever which is 10 times simpler, escecially when the next generation of the Co-ax will all run in 28,800bph.


I'm not sure how the splitting of the functions of one quite complex wheel into two far simpler wheels with a single function each adds much to the complexity of the escapement. Personally I'd say that this simplifies it. More to the point, I'm not clear what the added parts are. Perhaps a list would be helpful as I can't think of any *added* parts and there doesn't seem to be much of a change in the parts count. 


> The 2500D/8500 escapement is even more complicated than the previous 2500 with added parts so I still ignore how the Co-ax would last longer than a Swiss lever which is 10 times simpler, escecially when the next generation of the Co-ax will all run in 28,800bph.


I don't think it is more complicated and I certainly don't think that the coaxial is 'ten times' more complicated. A little bit more complicated sure, but mostly it's just different. I have explained how this difference makes the watch more stable elsewhere.



> At least one thing for sure now is that the 3-tier escapement seems to have a better handling of the power flow so the stoppage and the flick-to-start could be avoided.


The need to put a little energy in the system to start isn't a fault in the first place, but it was 'solved' with the C revision. The 'stoppages', which now seem to be accepted as a reality, are still only evidenced by less than fifty complaints over a three year period on WUS. As several million 2500 movements were made in that period and WUS is around the top of google for this search term (and the majority of complaints came from new members) I'd say we are looking at a clear case of sample bias giving a misleading impression. (But I've said this all before).

Omega say that they moved the 2500 to a three tier coaxial wheel to standardise the escapement between the 2500 and 8500. However, as I have hypothesised elsewhere (and we have argued to death previously) there seems to be a possibility that oil may migrate from the leading edge of the pinion of the coaxial wheel (which powers the escapement) to the trailing edge (which takes power from the intermediate wheel) and cause an issue. This would explain why Omega are so precise about the amount of oil used and the application of an epilame. In the 2500D the potential issue with oil migration is solved as the trailing edge of the pinion wheel has no function as power is delivered through an ordinary cog elsewhere on the coaxial wheel. This cog would not be terribly sensitive to oil migration even if the oil migrated that much further, which seems unlikely. In short, I'm not sure there is an issue with the coaxial escapement of the sort imagined by those who are not statistically minded, but *if *there were and *if *this were the problem, then it is solved.

However, in my experience,any fault at all, from a magnetised hairspring to needing a service seems to have been included in the '2500 problem' - there seem to be a very small number of watches for whom oil migration may have been a problem and an awful lot of people who joined WUS Omega to vent and left again. There is nothing wrong with doing this, but when added to the usual issues any movement will have it has given the 2500C an unfairly poor reputation. As far as I am aware there have been *no *complaints about the 2500B on WUS and less than ten about the 2500C in any other watch than the Planet Ocean.


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## M4tt (Jan 18, 2007)

> So how does changing the escape wheel in the repairs of nonworking 2500Cs resolve whatever underlying problem exists with the unmodified movement?


I don't believe that Omega modify the 2500C while performing repairs. I may be wrong, but I don't remember seeing any significant evidence of this



> What has Omega figured out about the 2500C that they think will be fixed by this switch?


I guess I answered this above. However, given that the 2500C has been one of Omega's most successful movements, in terms of sales, since the sixties adn they didn't change it for many years I'd guess that they didn't really think there was a problem, but have just been upgrading in the light of experience from the 8500 (which was a larger movement) To assume that an upgrade is automatically a response to a fault, rather than a natural process that is part of the life of any artifact manufactured over a long period seems odd. There were twenty four marks of Spitfire for example; this does not mean that the MKII which equipped the RAF during the Battle of Britain was a profoundly flawed aircraft, merely that as the state of the art moved forward the aircraft was updated to reflect this.


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## 6SpeedTA95 (Mar 19, 2010)

M4tt said:


> I don't believe that Omega modify the 2500C while performing repairs. I may be wrong, but I don't remember seeing any significant evidence of this
> 
> I guess I answered this above. However, given that the* 2500C has been one of Omega's most successful movements, in terms of sales, since the sixties *adn they didn't change it for many years I'd guess that they didn't really think there was a problem, but have just been upgrading in the light of experience from the 8500 (which was a larger movement) To assume that an upgrade is automatically a response to a fault, rather than a natural process that is part of the life of any artifact manufactured over a long period seems odd. There were twenty four marks of Spitfire for example; this does not mean that the MKII which equipped the RAF during the Battle of Britain was a profoundly flawed aircraft, merely that as the state of the art moved forward the aircraft was updated to reflect this.


What? I thought the 2500C made its debut in the PO and the first 2500 was put into mainstream production in 1999...not in the 1960s...


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## iinsic (Feb 18, 2010)

M4tt said:


> I don't believe that Omega modify the 2500C while performing repairs. I may be wrong, but I don't remember seeing any significant evidence of this


I guess, since Al at Archer Watches was the one who told me about the new escape wheel in the repaired 2500Cs, I should have just asked him why Omega does that. :roll:


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## Zidane (Feb 11, 2006)

6SpeedTA95 said:


> What? I thought the 2500C made its debut in the PO and the first 2500 was put into mainstream production in 1999...not in the 1960s...


He's saying the movement is *one* of the most successful movements, in terms of sales, *since* the sixties; not that it was actually sold in the sixties.


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## Archer (Apr 23, 2009)

iinsic said:


> So how does changing the escape wheel in the repairs of nonworking 2500Cs resolve whatever underlying problem exists with the unmodified movement? What has Omega figured out about the 2500C that they think will be fixed by this switch?


The technical guide for the 2500 doesn't give a lot of detail, but based on what I see there the change of the intermediate escape wheel is designed to eliminate a black residue forming that can cause low amplitude and stopping of the watch. The new wheel apparently has a different surface treatment.

Hope this helps.

Cheers, Al


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## iinsic (Feb 18, 2010)

M4tt said:


> I don't believe that Omega modify the 2500C while performing repairs. I may be wrong, but I don't remember seeing any significant evidence of this





Archer said:


> The technical guide for the 2500 doesn't give a lot of detail, but based on what I see there the change of the intermediate escape wheel is designed to eliminate a black residue forming that can cause low amplitude and stopping of the watch. The new wheel apparently has a different surface treatment.
> 
> Hope this helps.
> 
> Cheers, Al


Thank you, Al, for that clarification! :-!


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## Undersköterskan (Nov 4, 2006)

Excellent posts, M4tt !


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## lvt (Sep 15, 2009)

Dixan said:


> Dude, you have to stop putting out this bad information. Did I miss something, here? Unless something happened since the last time you made this same irresponsible, purely speculative statement, and Omega has since officially announced that the next generation of Co-Axial movements will again beat at a faster beat rate, then your statement once again comes across as nothing more than your _wish,_ stated as fact. Please stop stating things _you personally wish_ to see happen as factual, or otherwise officially planned. :roll:
> 
> EDIT: IDK, maybe word your statements in a way that conveys your desire for Omega to bring future Co-Axial movement beat rates back up, but doesn't necessarily (mis)state that that will happen for sure, or is in any way officially planned by Omega. You might not even be alone in wishing that would happen. I personally don't see it happening, but I guess we'll just have to see.


The 9300 caliber's escapement is nothing other than a modified version of the 8500's escapement and it beats at 28,800bph, so Omega actually mastered the Co-ax technology, adding a third wheel to the double escape wheel is a bit strange but apparently it works, should we call it Triple-ax instead of Co-ax ?

It's not my irresponsible statement but it's a reality, Omega always wanted to have a new escapement beating at the industry standard beat rate, if you make less than 1,000 watches per year, you are probably a very high-end brand and you can have your watches running at 21,600bph or even lower, it doesn't matter as you actually sell 45K watches, but when you want to sell hundreds thousands watches per year at lower price tags you are a major player on the field and you have to follow the standard before you can set a standard for others, in the case of Omega you'd better try to reach the standard 28,800bph rather than try to create a standard 25,200bph because noone would follow you.


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## drunken monkey (Jun 22, 2011)

but it is just supposition on your part.
it may be based on observations and it may actually be the case but unless it is confirmed by Omega that it is a firm company plan/policy/target, it is still just supposition.


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## lvt (Sep 15, 2009)

M4tt said:


> So, just to be clear, you are saying that they are both as reliable but the 2892 is more reliable because it is simpler?
> 
> Personally I think that simplicity is not obviously the key reason that something is reliable. Good, well executed design in high quality materials is usually the reason that something is reliable. Take a Russian Lada car engine. These are astonishingly simple and, in my experience, often have a total of *no *moving parts. A Mercedes engine is significantly more complex and yet manages to be infinitely more reliable. Likewise, a quartz watch is a far more complex design than a mechanical (if a little more inscrutable) and yet...


I didn't understand why did you compare a Lada to a Mercedes...

...until I read your later reply



M4tt said:


> I'm not sure how the splitting of the functions of one quite complex wheel into two far simpler wheels with a single function each adds much to the complexity of the escapement. Personally I'd say that this simplifies it. More to the point, I'm not clear what the added parts are. Perhaps a list would be helpful as I can't think of any *added* parts and there doesn't seem to be much of a change in the parts count.


You completely misunderstood what I want to say, I never mention the parts count in the comparison even if the lists are obviously different. What I want to say it's how they work, the complexity of the construction and number of moving parts involved in the action to achieve the same task. We used to hear that the Co-ax reduces friction but in fact how many of us are really worry about friction in a mechanical watch ? Unscrewing your watch's crown and manually wind the watch for 30 seconds will make more wears on the auto-winding mechanics than the amount of wear created by friction on the escapement in a whole month. People still buy sport cars and floor the gas pedal as soon as they have a chance to do so without fear of making wears in the engine.


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## Adam S (Oct 13, 2011)

I knew this would be a lively thread.


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## lvt (Sep 15, 2009)

drunken monkey said:


> but it is just supposition on your part.
> it may be based on observations and it may actually be the case but unless it is confirmed by Omega that it is a firm company plan/policy/target, it is still just supposition.


Doing so will lower the value of existing products and eventually raise some questions, better avoid it.


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## lvt (Sep 15, 2009)

M4tt said:


> So, just to be clear, you are saying that they are both as reliable but the 2892 is more reliable because it is simpler?
> 
> Personally I think that simplicity is not obviously the key reason that something is reliable. Good, well executed design in high quality materials is usually the reason that something is reliable. Take a Russian Lada car engine. These are astonishingly simple and, in my experience, often have a total of *no *moving parts. A Mercedes engine is significantly more complex and yet manages to be infinitely more reliable. Likewise, a quartz watch is a far more complex design than a mechanical (if a little more inscrutable) and yet...


Very funny comparison, helas totally incorrect when it comes to escapement, please don't forget that the Swiss lever can run as fast as 36,000BPH since decades thanks to its simplicity and functional prototypes with even higher beat-rate are ready, how that would be possible if it isn't reliable ?

The old 2500 is reliable as you might expect when you pay for it, but it isn't reliable enough to be Omega's long term workhorse that's why the radical change between the Daniel's Co-ax and Omega's Co-ax.


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## ddatta (Oct 6, 2009)

lvt said:


> ... Omega always wanted to have a new escapement beating at the industry standard beat rate, if you make less than 1,000 watches per year, you are probably a very high-end brand and you can have your watches running at 21,600bph or even lower, it doesn't matter as you actually sell 45K watches, but when you want to sell hundreds thousands watches per year at lower price tags you are a major player on the field and you have to follow the standard before you can set a standard for others, in the case of Omega you'd better try to reach the standard 28,800bph rather than try to create a standard 25,200bph because noone would follow you.
> ...


Can someone step in and explain this one to me, please?

I would have thought anyone making "_*hundreds thousands watches per year*_" was in a better position to set standards than someone making "_*less than 1,000 watches per year*_", if beat numbers can be standards in the first place.

And why would Omega care if anyone followed it or not? How would it matter at all to Omega if no one else made a watch running at any specific beat?


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## lvt (Sep 15, 2009)

ddatta said:


> Can someone step in and explain this one to me, please?


I'm here to defend my opinion.



ddatta said:


> I would have thought anyone making "_*hundreds thousands watches per year*_" was in a better position to set standards than someone making "_*less than 1,000 watches per year*_", if beat numbers can be standards in the first place.


The beat-rate is always a standard even if you don't agree, major manufacturer like ETA must control this standard because many other companies will buy, use and modify their movements, for example the 7750 has 28,800bph and it's a native chrono movement, but a 2824 or a 2892 also must have 28,800bph because it could also be a chrono too with a DD or Soprod module added, many companies use 28xx based chronograph instead of the ETA 7750. If you change the beat-rate there are a lot of parts must be changed accordingly to be compatible, not the thing you really want to do when you know how that ETA makes 75% of Swiss movement per year and other manufacturers like Sellita and Soprod also buy finished movements or parts from them.



ddatta said:


> And why would Omega care if anyone followed it or not? How would it matter at all to Omega if no one else made a watch running at any specific beat?


Of course they do, the Swatch Group will force them to do so, why should an Omega watch must run slower than a Calvin Klein or a Tissot (also in the same Group).


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## drunken monkey (Jun 22, 2011)

I can understand why 28,800 is a sort of standard for a movement that is sold to third parties and that may end up in a chronograph watch as that beat-rate gives a handy 1/4 second accuracy to time keeping but why does a movement in a regular 3 hand watch *need* to be 28,800, especially if that movement won't be serving as a host to a chronograph module or indeed, see service in any watch other than an Omega?

For the sake of keeping up with the Jones'?
For a smoother second hand?

Is it all that important if the movement is isochronous and reliable?

All I see, is more supposition made out to be known facts.


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## ddatta (Oct 6, 2009)

lvt said:


> ...
> Of course they do, the Swatch Group will force them to do so, why should an Omega watch must run slower than a Calvin Klein or a Tissot (also in the same Group).


You mean they are going to use the Co-Axial in these other watches too? (I dont even want to get into the slower/faster story)


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## lvt (Sep 15, 2009)

drunken monkey said:


> I can understand why 28,800 is a sort of standard for a movement that is sold to third parties and that may end up in a chronograph watch as that beat-rate gives a handy 1/4 second accuracy to time keeping but why does a movement in a regular 3 hand watch *need* to be 28,800, especially if that movement won't be serving as a host to a chronograph module or indeed, see service in any watch other than an Omega?


The reason is quite simple, actually the 93xx already run at the "normal" 28,800bph, there is no reason to keep two separated lines of escapement, if all Omega watches use the same type of escapement the making process and stock management will be 2 times simpler. It's the first thing you should do if you want to catch Rolex because they make watches very fast.



drunken monkey said:


> For the sake of keeping up with the Jones'?
> 
> For a smoother second hand?


For all of the above.



drunken monkey said:


> Is it all that important if the movement is isochronous and reliable?


For the same type of escapement, the one running faster will be more accurate than the other, this is also applicable to the traditional escapment.



drunken monkey said:


> All I see, is more supposition made out to be known facts.


When I said about the end of the 2500 caliber people say the same like you, 6 months later the first thread about the new 2500D appeared, helas, same caliber code but different thing.

So I understand that why you see things as suppositions : you see what people want you to see, that's it.


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## Mathew J (Oct 18, 2006)

lvt said:


> It's not my irresponsible statement but it's a reality, Omega always wanted to have a new escapement beating at the *industry standard beat rate*.


We're not talking USB, Blue ray, IDE, ATA, SATA or any other standards I can think of...there is no industry standard "beat rate"

If Omega wanted their watches to run at 28.8 then they should have done that with the release of the 8500, they weren't pressured to release the movement.


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## drunken monkey (Jun 22, 2011)

No, I see them as suppositions because you are making assumptions based on your observations without any firm facts.
As I said before, you may well be right in your assumptions but it is wrong that you make those assumptions to be known, confirmed facts.

I can say that the next Ferrari V8 will have more bhp than the current one in the 458 Italia.
I can also say that they will eventually re-introduce turbos to their mid engined V8 cars.

Both are suppositions.
Both are likely to happen.
Neither are known facts.


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## lvt (Sep 15, 2009)

Mathew J said:


> We're not talking USB, Blue ray, IDE, ATA, SATA or any other standards I can think of...there is no industry standard "beat rate"


Of course there is.

There is always a standard where you think it isn't, your car's speedometer suggests that you could go as fast as 240km/h right ? But in reality there is a standard speed allowed for each type of route (highway, city, mountain...), driving a Porsche doesn't mean you have the right to run faster than your neighbor who drives a Smart car, all cars must obey the "standard" speed to avoid accident.


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## hidden by leaves (Mar 6, 2010)

I think there are some issues in this thread stemming from certain technical and colloquial uses of the word "standard", i.e., requisite vs. commonly observed.


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## buddy13 (Sep 1, 2007)

There are many Seiko/Orient calibers running at 21,600 bph apart from the Blancpain fifty fathoms movement, which is not the standard 28,800 bph you mention...

They all do pretty well in my opinion!


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## sk0eric (Oct 18, 2011)

Doesnt only having 7 BPS make the coaxial kind of unique though? I like having something that is different from the other swiss brands. Also the coaxials that are either fixed or work properly (this is just my observation, this is in no way being saod as a factual statement) seem to run more accuratly than say some rolexs. Theyre all within COSC standards but my Coaxial is within +1 second a day and there are people ive talked to who have them sometimes even under a second a day. In fact I havent apoken to a person who ever had theirs running more that +3 seconds. again this is just my experience and observation.


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## M4tt (Jan 18, 2007)

> The 9300 caliber's escapement is nothing other than a modified version of the 8500's escapement and it beats at 28,800bph, so Omega actually mastered the Co-ax technology, adding a third wheel to the double escape wheel is a bit strange but apparently it works, should we call it Triple-ax instead of Co-ax ?


Nope. That's not why it is called a coaxial. (Good joke though)


> It's not my irresponsible statement but it's a reality, *Omega always wanted to have a new escapement beating at the industry standard beat rate*, if you make less than 1,000 watches per year, you are probably a very high-end brand and you can have your watches running at 21,600bph or even lower, it doesn't matter as you actually sell 45K watches, but when you want to sell hundreds thousands watches per year at lower price tags you are a major player on the field and you have to follow the standard before you can set a standard for others, in the case of Omega you'd better try to reach the standard 28,800bph rather than try to create a standard 25,200bph because noone would follow you.


Ok, *"Omega always wanted to have a new escapement beating at the industry standard beat rate*"is a pretty clear statement, you have made it many times. What I, and apparently a few others are not clear about, is why you are so sure this is Omega's desire; what actual grounds do you have for making this claim? It's not enough to argue that this is what Omega *should *want to do, you have to demonstrate that this is what Omega actually *do *want to do and that would have to be documentation from a definitive source. *Do you have any? *


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## M4tt (Jan 18, 2007)

> For the same type of escapement, the one running faster will be more accurate than the other, this is also applicable to the traditional escapment.


I'm afraid that this simply isn't true. The more conservative assertion that 'all things being equal, the watch with the faster beat rate will be more stable' isn't even true. It may be true for the lever escapement in watches, but I don't see any reason to believe it is true of the coaxial escapement, due to the fact that the impulse to the balance is shorter and sharper in the coaxial than in the lever. As a result, at higher frequencies such as 28,800 and 36,000 I suspect that the potential advantage from a higher rate is balanced by having an impulse which is just too sharp. (Think about pushing someone on a swing: there's a sweet spot but when you try to push the swing really sharply you spoil the dynamics of the whole swing.) As such, I suspect that the reason Omega have settled on 25,200 is it is the best all round compromise for a three hand watch. For a chronograph, the higher beatrate is move valuable as it makes for a more precise sweep seconds hand. This suggests to me that the advantage is pretty minimal.


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## hidden by leaves (Mar 6, 2010)

Hi Matt! Nice to see you... despite the Sisyphean circumstances ; ) 

Cheers,
Anthony


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## M4tt (Jan 18, 2007)

> Hi Matt! Nice to see you... despite the Sisyphean circumstances ; )
> 
> Cheers,
> Anthony


It's nice to see you too. Life good?

I have to admit, watching the usual nonsense become 'internet fact' by the simple technique of endless repeating has been a sad thing to watch. I don't think I have typed anything new yet...


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## M4tt (Jan 18, 2007)

> You completely misunderstood what I want to say,


That's great. Can you explain what you meant when you said



> I also think that the 2500 is as reliable as a 2892 but the 2892 has a big advantage : its simplicity, and* in mechanical stuffs simplicity means more reliability*.


then, because I misunderstand you as saying that 'the simpler something mechanical is, the more reliable it will be'.

Frankly, I'd argue that the 2500D is a simpler design than the 2500C as separating the three functions of the coaxial wheel on to three different levels means that the coaxial wheel is driven by a simple everyday cog rather than the significantly less traditional interaction between the trailing edge of the pinion wheel and the intermediate wheel while the leading edge of the pinion wheel does and entirely different job. Which is more complex, doing two things at once or two things separately?


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## GaryF (Dec 18, 2009)

lvt said:


> I'm here to defend my opinion.


As long as we are clear that's all it is. Your opinion.



> The beat-rate is always a standard even if you don't agree, major manufacturer like ETA must control this standard because many other companies will buy, use and modify their movements


ETA, Swatch or Omega do not sell co-axial movements to anyone. There is no "standard" to which it need comply.


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## hidden by leaves (Mar 6, 2010)

M4tt said:


> It's nice to see you too. Life good?
> 
> I have to admit, watching the usual nonsense become 'internet fact' by the simple technique of endless repeating has been a sad thing to watch. I don't think I have typed anything new yet...


I really can't complain, so life is good, yes. Thanks for asking, and hope the same for you.


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## M4tt (Jan 18, 2007)

> ETA, Swatch or Omega do not sell co-axial movements to anyone. There is no "standard" to which it need comply.


They do you know, a whole fifty a year!

Evening Gary, frog boiling anyone?


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## GaryF (Dec 18, 2009)

M4tt said:


> It's nice to see you too. Life good?
> 
> I have to admit, watching the usual nonsense become 'internet fact' by the simple technique of endless repeating has been a sad thing to watch. I don't think I have typed anything new yet...


Nice to see you, M4tt. 
At least we now know the lofty level of debate required to tempt you in.

I'm thinking of a "Can a dog tell the time?" thread. Interested?


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## M4tt (Jan 18, 2007)

> The technical guide for the 2500 doesn't give a lot of detail, but based on what I see there the change of the intermediate escape wheel is designed to eliminate a black residue forming that can cause low amplitude and stopping of the watch. The new wheel apparently has a different surface treatment.
> 
> Hope this helps.
> 
> Cheers, Al


So they are replacing the intermediate escape wheel (I'm a little surprised, I would have expected it to be the pinion wheel layer of the coaxial wheel) with one that has been treated (presumably) with epilame to combat oil migration? (as previously discussed to death). If this isn't the case, I'd be really interested in what the 'black residue' is as the inside of a watch is a fairly controlled environment...) Thinking on, why can't watchmakers simply apply something like Mobius 'Fixodrop' themselves?


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## M4tt (Jan 18, 2007)

> I guess, since Al at Archer Watches was the one who told me about the new escape wheel in the repaired 2500Cs, I should have just asked him why Omega does that. :roll:


I don't think you do have to as Archer has kindly explained in this very thread:



> The technical guide for the 2500 doesn't give a lot of detail, but based on what I see there the change of the intermediate escape wheel is designed to eliminate a black residue forming that can cause low amplitude and stopping of the watch. The new wheel apparently has a different surface treatment.


As I implied, it's a new bit of information for me - which is what 'I may be wrong' meant. As for what Archer said, I could be entirely wrong again, but I read this as saying that the same wheel has a different coating. I'm sure Archer will explain my error if I have made one, but I guess I don't consider a part with an epilame treatment to be a different part. Maybe this is just semantics, but I don't think Archer and I are at odds here. Of course I may be wrong, the 'black deposit' may not be tribological in nature, the treatment not an epilame and the wheel entirely different, but if that is the case I'm sure someone will explain that to me. Frankly, I don't claim to be anything more than an interested amateur and I would be delighted to have all the stuff I have had to work out over the years explained to me clearly by an expert. However I wouldn't presume on the time of a clearly very talented and thus extremely busy person

Funnily enough, the discussion a few years ago meandered into the idea that there was a bad batch of 2500C released sometime in 2009 (When there really were a cluster of watches exhibiting a very similar sort of failure.) At the time, I hypothesised that this batch could have not had an epilame treatment as found on (at least)my 2500B and this could have caused oil spreading on either the intermediate escape wheel or the pinion wheel of the coaxial wheel. If this was the case, either re-coating or replacing with a precoated part would solve the problem. Incidentally, the three level coaxial would solve this specific problem as well.

My key point has always been that this issue simply isn't at all common apart from a cluster of failures a few years ago.


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## M4tt (Jan 18, 2007)

> I'm thinking of a "Can a dog tell the time?" thread. Interested?


Actually, the psychology of canine time keeping may well be something that I could contribute to...

Circadian timekeeping in narcoleptic dogs. [Sleep. 1986] - PubMed - NCBI

They should let sleeping dogs lie.

However, the bottom line is 'yes'! Indeed in mammals, it is fascinating the number of different ways (some competing) that time is kept in the body! However, my real interest in this area is how time is represented in the brain, or more precisely, the binding problem:

Dennett on The Binding Problem - YouTube


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## GaryF (Dec 18, 2009)

Hold on. You said:


lvt said:


> You completely misunderstood what I want to say, *I never mention the parts count* in the comparison even if the lists are obviously different. What I want to say it's how they work, the complexity of the construction* and number of moving parts *involved in the action to achieve the same task.


That was in two consecutive sentences. And "how they work" and "the complexity of the construction" are not independent of the number of moving parts. They are both a result of it.

So you don't like M4tt's comparison. Here's another: Would you rather rely on three waiters carrying a loaded tray of champagne glasses each or one guy carrying all the three? Three independently operating organisms are more complex in their construction and the number of their moving parts than a single one yet, like the wheels of a three-tier co-axial, they have divided the larger, more complicated task into separate, less complicated tasks, with the result that they will more reliably get drinks to thirsty hedonists.

Sometimes a more complex system can be less reliable than a simple thing but it is not a law or fact of engineering. It may seem more elegant to have parts performing multiple tasks but the important thing is how any level of complexity is deployed.

And rather than get into what I suspect will be the inevitable debate about people not being mechanical (a can for which there simply aren't enough worms in the world), I'll say here that they are _robot_ waiters.:-d There, I've simplified the next ten posts by adding a word. It can be done.


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## GaryF (Dec 18, 2009)

M4tt said:


> Actually, the psychology of canine time keeping may well be something that I could contribute to...
> 
> Circadian timekeeping in narcoleptic dogs. [Sleep. 1986] - PubMed - NCBI
> 
> ...


Hmmm. I was thinking more along the lines of "Should I buy a dog an Omega?"


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## M4tt (Jan 18, 2007)

> And rather than get into what I suspect will be the inevitable debate about people not being mechanical (a can for which there simply aren't enough worms in the world), I'll say here that they are _robot_ waiters.:-d There, I've simplified the next ten posts by adding a word. It can be done.


But Gary, 'robot' is the Polish word for 'slave'. I'm shocked that you think that Polish Slave Waiters are less contentious than mere minimum wage meat machine waiters.


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## drunken monkey (Jun 22, 2011)

GaryF said:


> Hmmm. I was thinking more along the lines of "Should I buy a dog an Omega?"


and I thought I was the only who referred to the missus like that...
(man... I had to think carefully of how to use that without it possibly being misunderstood)


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## M4tt (Jan 18, 2007)

> Hmmm. I was thinking more along the lines of "Should I buy a dog an Omega?"


Ooops - it's dark up here!


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## GaryF (Dec 18, 2009)

M4tt said:


> But Gary, 'robot' is the Polish word for 'slave'. I'm shocked that you think that Polish Slave Waiters are less contentious than mere minimum wage meat machine waiters.


Doh!


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## lvt (Sep 15, 2009)

buddy13 said:


> There are many Seiko/Orient calibers running at 21,600 bph apart from the Blancpain fifty fathoms movement, which is not the standard 28,800 bph you mention...
> 
> They all do pretty well in my opinion!


That's true.

Seiko and Orient have their own standard and different market segments, the only things that count on a Seiko or Orient watches are 1) the watch looks good on me and 2) it keeps fairly good time, what do you want more for a sub-$200 watch ?

Seiko is also observing the Swiss counterpart's move and to compete with lower-end Swiss watches they do have the 6R20 caliber with similar features (hacking, hand-wind, 28,800bph, day-date...). If the 28,800bph is not a standard why did they bother to do that ? They should have kept their low-end watches running at 21,600bph and their Grand Seiko at 36,000bph, right ?

But when Seiko want to make a high-end watch, the Grand Seiko, things change, the beat-rate is raised to 36,000bph resulting in an excellent accuracy (better than COSC) and people appreciate that. On the Swiss side Zenith is known for making 36,000bph movements and their El Primero is considered the best Swiss chronograph movement.

Quote from the Wiki



> Zenith has a long reputation for the quality and precision of their watches, with 1,565 1st-place precision awards to date. It is one of few remaining Swiss watch manufacturers that still produce their own movements in-house - the Elite (standard movement) and the famous El Primero (chronograph). The El Primero, which was first released in 1969, was one of the first automatic chronograph movements and has a frequency of 36,000 alternations per hour. This high rate allows a resolution of 1/10 of a second and a potential for greater positional accuracy over the more common standard frequency of 28,800 alternations per hour.[2]


You see, I'm not alone to call the 28,800bph a "standard".


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## lvt (Sep 15, 2009)

drunken monkey said:


> No, I see them as suppositions because you are making assumptions based on your observations without any firm facts.
> As I said before, you may well be right in your assumptions but it is wrong that you make those assumptions to be known, confirmed facts.
> 
> I can say that the next Ferrari V8 will have more bhp than the current one in the 458 Italia.
> ...


I see what you want to say : what will be will be, right ?

When I see an approaching airplane with its landing gear slowly extending I know that the airplane will land at the nearby airport without the pilot telling me that. I actually make an assumption that will become a fact in the next minutes, unfortunately not all assumptions can become confirmed facts so quickly.


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## Will_f (Jul 4, 2011)

lvt said:


> That's true.
> 
> Seiko and Orient have their own standard and different market segments, the only things that count on a Seiko or Orient watches are 1) the watch looks good on me and 2) it keeps fairly good time, what do you want more for a sub-$200 watch ?
> 
> ...


Seiko was one of the first, if not the very first to go 36000 BPH. I've got an old King Seiko (not Grand Seiko & not Chronometer) dating from the late sixties. While its a great watch, I think they went high beat just to prove they could. The first Grand Seiko from the early sixties ran at 18000 BPH, which they upped to I think 19800 for better rate stability and to meet chronometer certification. 36000BPH (and some prototype 72000 BPH watches) were just Seiko being Seiko and pushing the envelope of what's possible. I don't think they were dramatically more accurate than their slower predecessors, but they did have shorter power reserves, required tighter manufacturing tolerances and required more frequent service.

Re simplicity being more reliable (all other things being equal). I can tell you as a professional design engineer with 25 years of experience that this is definitely true. Complexity can bring other advantages, and greater complexity matched with careful QC and engineering can provide great reliability.


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## M4tt (Jan 18, 2007)

> When I see an approaching airplane with its landing gear slowly extending I know that the airplane will land at the nearby airport without the pilot telling me that.


Ahh, I see, you are making an inductive inference.

So what precisely is the Omega equivalent of gear out, flaps down and lining up on final approach?


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## M4tt (Jan 18, 2007)

> Seiko was one of the first, if not the very first to go 36000 BPH. I've got an old King Seiko (not Grand Seiko & not Chronometer) dating from the late sixties. While its a great watch, I think they went high beat just to prove they could. The first Grand Seiko from the early sixties ran at 18000 BPH, which they upped to I think 19800 for better rate stability and to meet chronometer certification. 36000BPH (and some prototype 72000 BPH watches) were just Seiko being Seiko and pushing the envelope of what's possible. I don't think they were dramatically more accurate than their slower predecessors, but they did have shorter power reserves, required tighter manufacturing tolerances and required more frequent service.


I'm not so sure, people tend to forget that, for a while, ETA offered many of their calibres in 36,000. I think that it was perceived as a logical next step for highbeat watches for a while before many people settled back to 28,800 as juggling the compromises most adequately for the manufacturing techniques and materials available. I bet that once silicon becomes far more common manufactures will take advantage of the material to look at even higher beat rates. I also have a 4502 and I have to say that over forty years on it remains a truly splendid watch that looks more modern on the inside than many of today's offerings.



> Re simplicity being more reliable (all other things being equal). I can tell you as a professional design engineer with 25 years of experience that this is definitely true. Complexity can bring other advantages, and greater complexity matched with careful QC and engineering can provide great reliability.


It's the *all things being equal* bit that matters here - in the case of the 2500D I think Gary nailed it with the waiter analogy.


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## lvt (Sep 15, 2009)

M4tt said:


> So what precisely is the Omega equivalent of gear out, flaps down and lining up on final approach?


This is the Airforce One, it's scheduled but nobody knows "when" and "where" (security and other obvious purposes), surprise guaranteed.


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## ChronoScot (Oct 25, 2010)

lvt said:


> Good explanation, M4tt, as usual.
> 
> I also think that the 2500 is as reliable as a 2892 but the 2892 has a big advantage : its simplicity, and in mechanical stuffs simplicity means more reliability.
> 
> ...


Your assertion that simplicity of a mechanical system automatically leads to more reliability is, in itself, a gross oversimplification.

The reliability of a system is determined by the Mean Time Between Failure (MTBF) values of its individual sub-systems or components. If you take a given system and _add _functionality to it by adding further sub-systems or components (each of which has a certain MTBF), then the reliability of the resulting system will be lower.

However if you compare two systems that have the _same _overall function (to display time), but achieve this with sub-systems or components that are designed in different ways or have different sub-functions, then you cannot use the part count as a measure of reliability. You are comparing apples with oranges and you need to have knowledge of MTBF of the sub-systems or components for each of the two systems to make any kind of objective comparison.

The MTBF of sub-systems or components are determined by a multitude of factors. What are the forces generated in the system and how will they tend to cause high stress, wear and fatigue to components? What is the restoring force that must be imparted by a balance spring to achiveve a given balance frequency (higher beat requires higher restoring force) an how are the bearings and balance wheel designed to cope with this? What are the frictional forces being generated between components and what level of wear does this cause? Is the layout conceived to effectively avoid the negative effects of contamination build-up and lubricant degradation over time? What is the efficiency of power transmission between elements of the power train? The list goes on...

The determination of these parameters is most likely beyond any of us posting here, as is the ability to collect data on actual failures rates of entire watches let alone individual components.

So speculating on which escapement concept is more reliable is little more than that. Speculation. Not to say that discussion cannot be interesting and should not take place on such a forum. However before attempting to elevate speculation and opinions to facts, I suggest bearing these points in mind.


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## M4tt (Jan 18, 2007)

> You see, I'm not alone to call the 28,800bph a "standard".


Maybe, but you are confusing that notion of standard with several other meanings of the word and it is this equivocation that allows you to say what you are saying. The fact is that the 28,800 beat rate is simply the best balance of compromises for many watch makers using modern technology and the lever escapement and that is why it is quite often used. Where is isn't the best compromise other beat rates are used.

In the case of the coaxial escapement, there is a lot of evidence that the lower beat rate is the optimum compromise (except when it isn't - for a chronograph, the higher beat rate offers higher precision) This is the whole point: different escapements have different optimum rates (but away from the balance and escapement, lower is always better!) . To compare the coaxial to the lever in this way is simply to ignore this fact.


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## M4tt (Jan 18, 2007)

> This is the Airforce One, it's scheduled but nobody knows "when" and "where" (security and other obvious purposes), surprise guaranteed.


I think I see the connection, but I'm afraid I have to tell you that Sarah Palin was never elected president and so I'm not sure the analogy works...


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## GaryF (Dec 18, 2009)

lvt said:


> This is the Airforce One, it's scheduled but nobody knows "when" and "where" (security and other obvious purposes), surprise guaranteed.


But that's the thing, isn't it? You are the only one who thinks "Airforce One" is coming and it's based, not any evidence or information from Omega, but simply on the idea that you think Airforce One _should _come. You haven't seen the landing gear because you haven't even seen (or heard) the plane. You have no information at all to base your belief on.
This then, in your mind, becomes a "fact" waiting to happen which you will repeat here relentlessly to the exasperation of pretty much every other poster in the thread. 
Can you please just learn to write "I think" or "in my opinion" so that you don't derail every thread of this type in which you participate into a series of requests for evidence that simply doesn't exist?


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## joslar (Jan 13, 2010)

ChronoScot said:


> Your assertion that simplicity of a mechanical system automatically leads to more reliability is, in itself, a gross oversimplification.
> 
> The reliability of a system is determined by the Mean Time Between Failure (MTBF) values of its individual sub-systems or components. If you take a given system and _add _functionality to it by adding further sub-systems or components (each of which has a certain MTBF), then the reliability of the resulting system will be lower.
> 
> ...


Joy to read your post ChronoScot! Only issue I have, is the part with the restoring force. If you achieve the higher frequency by reducing the inertia of the balance wheel, the spring force will not increase. But that's just a detail  Really nice post - I learned something there!


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## ChronoScot (Oct 25, 2010)

joslar said:


> Joy to read your post ChronoScot! Only issue I have, is the part with the restoring force. If you achieve the higher frequency by reducing the inertia of the balance wheel, the spring force will not increase. But that's just a detail  Really nice post - I learned something there!


Thanks, I'm glad you liked it!

Yes, you're absolutely right about the required spring restoring force being reduced by using a lower inertia balance wheel, I should have qualified that statement.

In saying that, this is where the real engineering comes in, to find the sweet spot between different (and sometimes contradictory) requirements of a system. For example, reducing the inertia of a balance wheel made from a given material will require material to be removed and/or redistributed. The impact of e.g. stress in the spokes might then become critical, so subsequent design choices might be to change the diameter or to select an alternative material or... several other possibilities. Finding the optimum might require compromise, but this is the iterative nature of engineering a system.

Anyway, now I'm the one speculating, but this is to illustrate my point that comparing reliability of two complex systems does not come down to simply counting the parts and concluding that the one with less "complexity" is better.


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## joslar (Jan 13, 2010)

ChronoScot said:


> Anyway, now I'm the one speculating, but this is to illustrate my point that comparing reliability of two complex systems does not come down to simply counting the parts and concluding that the one with less "complexity" is better.


I completely agree!


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## GaryF (Dec 18, 2009)

ChronoScot said:


> Anyway, now I'm the one speculating, but this is to illustrate my point that comparing reliability of two complex systems does not come down to simply counting the parts and concluding that the one with less "complexity" is better.


Oh, no. You could have told me before I took all these bearings out these rotor assemblies.


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## ChronoScot (Oct 25, 2010)

GaryF said:


> Oh, no. You could have told me before I took all these bearings out these rotor assemblies.


Yep, that's definitely going to lead to some nasty scraping noises...


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## Archer (Apr 23, 2009)

M4tt said:


> So they are replacing the intermediate escape wheel (I'm a little surprised, I would have expected it to be the pinion wheel layer of the coaxial wheel) with one that has been treated (presumably) with epilame to combat oil migration? (as previously discussed to death). If this isn't the case, I'd be really interested in what the 'black residue' is as the inside of a watch is a fairly controlled environment...) Thinking on, why can't watchmakers simply apply something like Mobius 'Fixodrop' themselves?


Not sure why this surprises you, but that is what has been indicated in the technical guide. I assume the black residue is a product of friction between the adjacent parts, and no matter where this forms it would be an impediment to the proper function of the escapement area. The old wheel is a yellow/gold colour and the new one is grey, and has an "improved" surface treatment according to the tech guide - no other specifics are given however.

I don't think epilame is relevant to this issue (the formation of residue is not necesssarily migration of lubricant), but as an FYI most watch movements are treated all over with epilame at the factory. At service specific parts are treated with epliame - I do it every day, but only those specified in the tech guides.

Cheers, Al


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## M4tt (Jan 18, 2007)

> Not sure why this surprises you, but that is what has been indicated in the technical guide.


That's simple, in this forum's seemingly endless discussions of the so called 'oiling issue' the usual suspect is the coaxial wheel (and specifically the coaxial wheel's interaction with the intermediate wheel. Mind you, that hypothesis has been based around the notion that oil migration was the culprit, and you appear to be offering an alternative hypothesis: that that the issue is wear. 


> I assume the black residue is a product of friction between the adjacent parts,


That's an interesting hypothesis, however, when talking about 'the products of friction' we are talking about a number of processes: there are three fundamental physical processes: erosion (the friction causes wear) transportation (the friction, or some other process, carries the eroded material away from the site of erosion) and deposition (the material ends up collecting somewhere. So we have a *deposit *but, if it is caused by friction, we don't have an answer to the questions where did it come from? (where is the wear?) how did it get there and where *precisely *did it end up. Obviously, there are also chemical processes in play whenever two metals, alloys or coatings of different reactivity interact, but I would rather hope that Omega are on top of this sort of interaction as it isn't as novel as the physical interaction between the coaxial and intermediate wheel.

The oiling hypothesis was based on a number of premises: the fact that over oiling of these parts was a significant issue for the 2500A, the fact that Omega are extremely specific about their oiling instructions for the 2500 family (I'm aware that oil is really only playing a cushioning role here though) and *explicitly *specify that 'there must be no oil between tooth and pinion' and circle in the diagram on page ten of the service manual published by cousins, the precise area we are discussing.

http://www.cousinsuk.com/PDF/categories/1013_Omega 2500C.pdf

More to the point, the oiling hypothesis has a clear process by which failure may occur, involving the migration of the oil from the leading edge of the pinion wheel (which interacts with the lever) to the trailing edge of the pinion wheel (which interacts with the intermediate wheel) This is why the effectiveness or lack of an epilame (or some other oil coating which inhibits oil spreading) is of some interest to me.



> and no matter where this forms it would be an impediment to the proper function of the escapement area.


I'm not sure I agree that wherever (on the intermediate or coaxial wheels) this deposit ended up it would form an impediment. These wheels have adequate torque and, unlike the balance, do not rely on careful poising to work correctly. Thus, unless the deposit is directly interacting with a moving part or has really significant relative mass, I don't think it would make much difference. If I am incorrect I'm sure you will be able to explain my error.



> The old wheel is a yellow/gold colour and the new one is grey, and has an "improved" surface treatment according to the tech guide - no other specifics are given however.


That's interesting, but what would be really telling is the nature or role of the coating. If it was something like teflon and concerned with reducing friction that would suggest one hypothesis. However, if it was something like stearic acid and designed to minimise oil spreading then that would suggest the other. I would assume that this is something that you would be able to discover. Certainly now that you have suggested such an interesting alternative hypothesis I will have a go at finding out myself.



> I don't think epilame is relevant to this issue (the formation of residue is not necesssarily migration of lubricant),


I can see how you would think that given the hypothesis that you are putting forward. However, given that there is already a fairly well developed hypothesis that appears to fit the known facts, I'd say that the question of how this residue forms, where it comes from and what it is made of, becomes extremely relevant as it would halp to differentiate between the two theories on offer. (However, from my experience of black residues in a number of engineering context, including horology, they often turn out to be a mixture of fractions of lubricant and the deposited products of friction, oxidation and so on. As such the question of which came first may be a moot one. 


> but as an FYI most watch movements are treated all over with epilame at the factory.


I am fully aware of that. If you read back, you will notice that one hypothesis I suggested was that this didn't happen, which may suggest that I was aware that it usually did. 


> At service specific parts are treated with epliame - I do it every day, but only those specified in the tech guides.


Again, I am aware of this, I even have a little bottle of fixodrop myself for when I am in the mood to wreck a movement in the name of self improvement. However, given that an epilame does not seem to be suggested at service and that oil migration clearly is *a* problem, even if it isn't *the *problem, I would suggest that this gives us a clue to the role of the mystery coating. My hypothesis is that the coating is (at least partially) to reduce oil spreading still further.

However, while speaking with authority with a manual in front of you certainly makes your case a strong one, I'd be curious to see a little more of the reasoning for your assumption about the nature of the residue, some idea of the residue's origin, the nature of the new coating on the wheel.

It's fantastic to have someone with real knowledge contributing to this discussion. I really enjoyed your infomercial write up on the 7750 based movement (it's one of the reasons I decided to try posting again) and I'm delighted to see the development of the trend of people offering services to this forum choosing to take an active role in the life and discussions of the forum. I'm really looking forward to informed answers to my naive questions.


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## M4tt (Jan 18, 2007)

Sorry I didn't say earlier, but that was a lovely explanation.


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## M4tt (Jan 18, 2007)

> The determination of these parameters is most likely beyond any of us posting here, as is the ability to collect data on actual failures rates of entire watches let alone individual components.


Great post, however, I think that it is possible to make a ball park hypothesis about the 2500C and the 2500D - in the case of the C you have a novel technique for delivering power both between the intermediate wheel and the escapement, as well as a single wheel being used for two entirely different roles - powering the lever and receiving power from the intermediate wheel.

In the 2500D you have a very traditional wheel and cog delivering the power to the coaxial wheel (which I would suggest is likely to be more reliable than the novel solution (especially as the novel solution has been dropped! and the pinion wheel of the coaxial wheel now does only one job without any compromise to a second role.

In short, the removal of a novel solution for one which is about as proven as available in watchmaking and the removal of a compromise solution for a solution which is only trying to solve a single problem at a time suggests to me that the interaction between the intermediate wheel coaxial wheel and lever has been made significantly more reliable. As for the complexity issue, as Gary put it, which is more complex - a single overloaded waiter or two lightly loaded ones?

Right, I'm taking my baby (she's doing fine BTW) up to London to spoil her!


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## Archer (Apr 23, 2009)

Wow - lengthy response. I actually don't have time to address each issue specifically - sorry but if I'm not at the bench, I'm not making a living.

As an engineer, I understand lubrication, friction, issues with materials etc., but thanks for the lessons anyway. I have no direct knowledge of what the coating is, or what the residue is. It takes very little to cause issues in a watch, so if the residue was in the leaves of the pinion or on the teeth then it would cause issues (that's what I meant when I said anywhere - in other words not just on the coaxial wheel). The oiling procedures and epliame procedures have not changed in this tech guide - the only thing that changed was this wheel. I am not here to propose competing theories and battle it out at length over minute details - I will leave that to others. I presented what I knew from information gathered from the technical guides.

In my view, speculating about this is really pointless. There was a problem, and Omega have offered a solution. I'm sure they know the reasons behind it all.

Cheers, Al



M4tt said:


> That's simple, in this forum's seemingly endless discussions of the so called 'oiling issue' the usual suspect is the coaxial wheel (and specifically the coaxial wheel's interaction with the intermediate wheel. Mind you, that hypothesis has been based around the notion that oil migration was the culprit, and you appear to be offering an alternative hypothesis: that that the issue is wear.
> 
> That's an interesting hypothesis, however, when talking about 'the products of friction' we are talking about a number of processes: there are three fundamental physical processes: erosion (the friction causes wear) transportation (the friction, or some other process, carries the eroded material away from the site of erosion) and deposition (the material ends up collecting somewhere. So we have a *deposit *but, if it is caused by friction, we don't have an answer to the questions where did it come from? (where is the wear?) how did it get there and where *precisely *did it end up. Obviously, there are also chemical processes in play whenever two metals, alloys or coatings of different reactivity interact, but I would rather hope that Omega are on top of this sort of interaction as it isn't as novel as the physical interaction between the coaxial and intermediate wheel.
> 
> ...


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## ChronoScot (Oct 25, 2010)

M4tt said:


> Great post, however, I think that it is possible to make a ball park hypothesis about the 2500C and the 2500D - in the case of the C you have a novel technique for delivering power both between the intermediate wheel and the escapement, as well as a single wheel being used for two entirely different roles - powering the lever and receiving power from the intermediate wheel.
> 
> In the 2500D you have a very traditional wheel and cog delivering the power to the coaxial wheel (which I would suggest is likely to be more reliable than the novel solution (especially as the novel solution has been dropped! and the pinion wheel of the coaxial wheel now does only one job without any compromise to a second role.
> 
> ...


Hi Matt. Yes, I agree. The replacement of a component which serves two distinct functions with two separate components, each of which is optimised for one of the two functions, can result in a more reliable arrangement than the original situation, in spite of the apparent increase in complexity to the casual observer.

This is particularly the case with respect to gear transmission, for which the shapes of gear teeth and pinion leaves are optimised to ensure that the direction of the transmitted force is perpendicular to the point of contact at the mid-point of the motion as well as to minimise power transmission losses before and after this point*. It becomes a challenge to define the shape of the small escapement wheel teeth to optimally perform the dual function of impulsing a pallet and transmitting power from the gear train.

Interestingly, George Daniels devised this concept as an _adaptation_ of the "basic" co-axial escapement. In _Watchmaking (2011 Edition), pp 247-250_, he describes this as the "Extra Flat Co-Axial Escapement", a compromise solution for use in thin watches having movements as thin as 2mm (quite ironic really, given feedback on the thickness of the cal 8500). I have taken the liberty of scanning some of the relevant pages for the full description and illustrations [I hope I am not contravening copyright rules by attributing the source, moderators please advise and I can remove these scans if necessary]:



















I would speculate that George Daniels devised this escapement on paper and potentially built prototypes and/or incorporated it into some of his watches. However Daniels did not have the benefit of feedback from having this design mass produced. Omega now has this feedback, having incorporated this co-axial variation into hundreds of thousands of watches in the last 10 years i.e. the 25xx series. I would further speculate that, based on this feedback (watches that have come in for service or warranty repair), they have chosen to implement the "basic" co-axial design in the cal 8500 and cal 2500D in order to have two distinct functions performed by components specifically optimised for each, but at the _expense _of movement thickness.

If this would be the case, it is a typical example of engineering compromise and the continuous improvement cycle to balance the multiple requirements of a design in achieving an optimal outcome.

_* For those who are interested in understanding how gear teeth and pinion leaves are shaped to optimise power transmission, this link provides a pretty good explanation: Gearing: Introduction_


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## M4tt (Jan 18, 2007)

> Wow - lengthy response. I actually don't have time to address each issue specifically - sorry but if I'm not at the bench, I'm not making a living.


That's fine, I guess I'm lucky enough to have a little more leisure time and this forum is, intermittently, a leisure activity. However, I would argue that taking an active role in the life of this forum is probably time well spent as it raises your business' profile and, frankly, you simply can't buy advertising like that.



> As an engineer, I understand lubrication, friction, issues with materials etc., but thanks for the lessons anyway.


Sorry if I insulted, as this is a forum with many people on it, I wrote for a more general audience than merely you and addressed the points you made; to have a deposit that you felt was caused by the products of wear and not be interested in the wear struck me as odd and I was encouraging you to elucidate. However, I guess I should have felt the same way about your epilame 'FYI' but I took it in the spirit described above.



> I have no direct knowledge of what the coating is, or what the residue is. It takes very little to cause issues in a watch, so if the residue was in the leaves of the pinion or on the teeth then it would cause issues (that's what I meant when I said anywhere - in other words not just on the coaxial wheel).


Sorry, I took 'anywhere' as meaning _anywhere _on the component rather than on other components. Don't you think it would be interesting to know what the coating is or what the residue is? This has been debated at length over many years here at WUS and certainly has been of interest to many people over these discussions. I'm reminded of a cartoon I saw a while back:









I guess I'm just more the mad scientist here.



> The oiling procedures and epliame procedures have not changed in this tech guide - the only thing that changed was this wheel.


I gathered that, but are you not even slightly curious about what was changed about the surface coating of the wheel? I assume you have worked on these movements, what did you observe?



> I am not here to propose competing theories and battle it out at length over minute details - I will leave that to others.


That's absolutely fine, adding any new detail to what is an ongoing discussion is very helpful in its own right. Some people are interested in minute detail and understanding the whys and wherefores - especially in a thread asking about the differences between the revisions - the answer that the difference is that 'one has a wheel which has a gold coating and one has a wheel with a grey coating' seems strangely unsatisfying to me. However, I accept that some people see such discussions as pointless. It takes all kinds to make the world. It's just great to get a contribution from an expert. 


> I presented what I knew from information gathered from the technical guides.


And that is really helpful given that the guides you have access to are not publicly available as far as I am aware. I genuinely appreciate it, in whatever spirit it was offered.



> In my view, speculating about this is really pointless. There was a problem, and Omega have offered a solution. I'm sure they know the reasons behind it all.


Are you _really _saying that we should simply be passive consumers without question or curiosity? I'd really hope that Omega do know the reasons behind it as well as failure rates and all the other issues we have spent years discussing, but they are not telling and I, for one, would really rather like to know. Even if we cannot find out for sure then at least we learn about our hobby as we go along and can share what we learn. That's the major interest of WUS Omega for me.


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## M4tt (Jan 18, 2007)

> I would speculate that George Daniels devised this escapement on paper and potentially built prototypes and/or incorporated it into some of his watches. However Daniels did not have the benefit of feedback from having this design mass produced. Omega now has this feedback, having incorporated this co-axial variation into hundreds of thousands of watches in the last 10 years i.e. the 25xx series. I would further speculate that, based on this feedback (watches that have come in for service or warranty repair), they have chosen to implement the "basic" co-axial design in the cal 8500 and cal 2500D in order to have two distinct functions performed by components specifically optimised for each, but at the _expense _of movement thickness.


It looks to me like you have turned your considerable engineering acumen onto understanding the Cal.2500 in more depth since we last discussed this. It's nice to see! However, as I always say, watches are about choosing compromises - I think I read somewhere about a new production method that made the three level coaxial wheel viable in the 2892 body which is, as you know, quite thin. I'm sure someone here will have references.


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## aardvarkbark (Oct 27, 2010)

Archer said:


> The technical guide for the 2500 doesn't give a lot of detail, but based on what I see there the change of the intermediate escape wheel is designed to eliminate a black residue forming that can cause low amplitude and stopping of the watch. The new wheel apparently has a different surface treatment.
> 
> Hope this helps.
> 
> Cheers, Al


Thank you for taking the time to chime in Al. I appreciate the perspective of one who works on several of these movements daily and who has first-hand knowledge of any direction and explanation provided by the manufacturer. As an owner I find your contributions practical, meaningful and beneficial.


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## Adam S (Oct 13, 2011)

I think the new production method uses LIGA technology. It's mentioned in this thread.

http://wusmob.com/wus/oldest564551/A_couple_of_things_about_my_PO_2500D


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## Archer (Apr 23, 2009)

M4tt said:


> Are you _really _saying that we should simply be passive consumers without question or curiosity? I'd really hope that Omega do know the reasons behind it as well as failure rates and all the other issues we have spent years discussing, *but they are not telling *and I, for one, would really rather like to know. Even if we cannot find out for sure then at least we learn about our hobby as we go along and can share what we learn. That's the major interest of WUS Omega for me.


Hi Matt - There seems to be a disconnect between us of me writing something, and you taking it in a completely different way than I meant it. Hopefully the rest of this post will give you a better view of my position on this matter.

I didn't mean to come off as uninterested, and by no means did I suggest you become a sheep-like consumer. Omega is not likely to tell you what the coatings are, and what the real issues were - you said it yourself above where I have highlighted the text. This is why I said speculating is pointless, because I doubt we will ever know for sure, and it does not change the way the situation is handled by the watch repairer. I would think for commercial/competition reasons alone, they would be hesitant to give up such information - coatings are a "big thing" in watchmaking so this is likely proprietary information..

I know these things are fascinating to some to dissect in detail on a forum, but the approach in my shop is a bit more practical. My goal is satisfied clients, and if Omega tells me that I need to replace "A" with "B" in order to make that happen, that's the "essential" information I need to know to run my business properly. Am I interested in what the real issues were? As an engineer and watchmaker I certainly have a natural curiosity about these things, but I know answers (verified by Omega) are not likely coming any time soon. Another example is servicing a Sinn Diapal movement - I have no idea what the coating is on the escape wheel that they use, but Sinn has told me I don't need to oil the escapement, so I don't, and the watch runs fine (I admit it felt odd not to oil the escapement on a watch, but it had great timing and amplitude numbers, so no argument from me).

Hope this helps.

Cheers, Al


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## M4tt (Jan 18, 2007)

Yes, I'd say that I misread your intention there. Frankly I _was _surprised as you have written up some splendid explanations - such as the recent explanation of the date fault. The way you homed straight in on the most probable fault really demonstrates the difference between the pro and the amateur. We agree that Omega are not telling, but we do have their products, the way they fail (when they fail) what we know of their development history and so on, to piece together a theory, and for a dilettante such as myself, that can be interesting in itself. I can see how that may be less interesting if it is your livelihood and you are paid by results not theories. However, one thing that we do have is this 'black deposit' and I would be both fascinated and grateful if you were able to offer a conjecture about it (and even photographs) when you next encounter it during a repair.

To reiterate, it really is delightful to see your splendid posts, I really like the open way that you appear to do business and it pains me that, for whatever reason, we appear to have ended up antagonising each other.


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## Runitout (Aug 19, 2009)

Great conversation; thanks for that.


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## Archer (Apr 23, 2009)

M4tt said:


> To reiterate, it really is delightful to see your splendid posts, I really like the open way that you appear to do business and it pains me that, for whatever reason, we appear to have ended up antagonising each other.


Thanks - and sorry if I came off as being blunt or short - the time I have for watch forums is not great these days, as I am trying to get watches out the door for those who want them back for the holidays. As you can imagine, my deadline is pretty much here for that!

Most likely my short replies added to the disconnect, so I apologize for that. Glad you have enjoyed the posts - I am here to try to help people where I can.

Thanks - Al


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## lvt (Sep 15, 2009)

ChronoScot said:


> Your assertion that simplicity of a mechanical system automatically leads to more reliability is, in itself, a gross oversimplification.
> 
> The reliability of a system is determined by the Mean Time Between Failure (MTBF) values of its individual sub-systems or components. If you take a given system and _add _functionality to it by adding further sub-systems or components (each of which has a certain MTBF), then the reliability of the resulting system will be lower.
> 
> ...


Glad to hear from you again, CS

You said about "friction" ?

You certainly remember that the Co-ax escapement's service interval is dramatically reduced from an early advertissed 10-year to a regular 6-year interval which is de facto another Swiss standard, there must be something wrong, right ?

So again we have the drawing of the Swiss lever and the Co-ax as below :










We all know that watch movement need servicing from time to time to free the components from the aged oil that with the build-up dust particles became sticky, it creates a drag in the movement instead of reducing friction, and there is oil where there is bushing, gear or pinion.

Let's take a look at the drawing, the Co-ax escepement is designed to eliminate a problem that happens in the lever escapement : the friction created by the contact between the escape wheel's tooth with the pallet. But the problem is that another part is added into the Co-ax escapement and this part itself needs oiling as it also creates friction and eventually caused the power loss in the early design of the Co-ax (being a moving part it also consumes power). The new Co-ax design has a stronger and more constant power flow to feed the 3-tier escapement (by using either a dual-barrel setup or a stronger mainspring).

In fact the friction problem with the lever escapement is no longer a true problem today as the steel escape wheel will be replaced by a silicon escape wheel (already used in some expensive watches like Patek Philippe), so technically speaking the problem is solved by a simple and reliable method that requires no extra moving part and technical headaches.

The only benefice from the Co-ax is the exclusivity, nothing else, you pay for the exclusivity, not the superiority.

So back to our main subject of the discussion (2892 vs 2500 let alone the difference about beat-rate which is in the favor of the 2500), are they equal in term of reliability ? Of course not.

If two watches (one with lever, other with Co-ax) are regularly serviced every 5-year interval they probably are equal (with the Co-ax requiring more attention and time for servicing). But if you let them run untill they break I doubt that the Co-ax will last longer than the other one, especially when both of them run at the same frequency of 28,800bph (like the cal. 9300 and next Co-ax generation), higher frequency means more power needed and more stress on component, the more components you put in a device, the more friction and wear you will have.

You should know better than me that in a micro-machine like watch movement the components are very sensible to wear and friction. In a two devices with a similar volume and function (e.g two three-handed watches with 2892 & 2500) the one with more parts would be more prone to problem. There would be exception only when the 2892 is poorly designed which is not the case.


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## M4tt (Jan 18, 2007)

> You certainly remember that the Co-ax escapement's service interval is dramatically reduced from an early advertissed 10-year to a regular 6-year interval which is de facto another Swiss standard, there must be something wrong, right ?


 Apart from the minor detail that six years isn't really a Swiss Standard, it doesn't mean anything is wrong at all, the fact is that whatever the escapement may be capable of, the rest of the watch is an ordinary watch and thus slave to lubrication. Omega made a silly claim and then backtracked on it. That is all.


> So again we have the drawing of the Swiss lever and the Co-ax as below :
> 
> 
> 
> ...


 So oil fails due to the build up of dust? Ok...


> Let's take a look at the drawing, the Co-ax escepement is designed to eliminate a problem that happens in the lever escapement : the friction created by the contact between the escape wheel's tooth with the pallet. But the problem is that another part is added into the Co-ax escapement and this part itself needs oiling as it also creates friction and eventually caused the power loss in the early design of the Co-ax (being a moving part it also consumes power). The new Co-ax design has a stronger and more constant power flow to feed the 3-tier escapement (by using either a dual-barrel setup or a stronger mainspring).


 The thing is that friction in one area merely causes wear (as long as it isn't so great to reduce the available torque, while the _variations _in friction in the other area don't just cause friction but also cause instability due to (in the short term) things like variations in viscosity due to temperature and (in the long term) changes in viscosity and simple lack of oil.


> In fact the friction problem with the lever escapement is no longer a true problem today as the steel escape wheel will be replaced by a silicon escape wheel (already used in some expensive watches like Patek Philippe), so technically speaking the problem is solved by a simple and reliable method that requires no extra moving part and technical headaches.


 Qua wear that may be true, qua stability it isn't due to the scraping action rather than the coaxial's rolling action.


> The only benefice from the Co-ax is the exclusivity, nothing else, you pay for the exclusivity, not the superiority.


 Well, it's a bit like the 'What have the Romans ever given us sketch' The Cal.2500 offers no benefits apart from: * Due to a rolling rather than a sliding action the pallet stones do not need lubrication and friction is reduced by about 95%. obviously this removes two major areas of instability in one: variations in the sliding surface due to bedding in and variations in the oil consistency due to age and temperature. * The freesprung balance is far, far nearer to the mathematical ideal as it doesn't have a regulator interfering with the spring. This helps with all forms of stability, including, of course, positional stability. * The impulse from the pallet stones is identical in both directions, unlike every other watch on the planet. This gives a smoother more regular swing to the escapement and reduces the effects of position still further. * The escapement is in contact with the balance for a far shorter period allowing more of the balance's swing to be free of interference, once again far closer to the mathematical ideal. (this, of course, can also reduce the effect of position) * Wear on the contact surfaces of the escapement has been almost entirely eliminated. * As a net effect stability which was described by one of the UK's greatest horological statisticians as "equivalent to a marine chronometer in gimbals". But apart from that, I'm sure you are quite correct.


> So back to our main subject of the discussion (2892 vs 2500 let alone the difference about beat-rate which is in the favor of the 2500), are they equal in term of reliability ? Of course not.


 Well, as you haven't proven your case theoretically, I guess you are going to prove it empirically. Where's your evidence for this claim?


> If two watches (one with lever, other with Co-ax) are regularly serviced every 5-year interval they probably are equal (with the Co-ax requiring more attention and time for servicing). But if you let them run untill they break I doubt that the Co-ax will last longer than the other one, especially when both of them run at the same frequency of 28,800bph (like the cal. 9300 and next Co-ax generation), higher frequency means more power needed and more stress on component, the more components you put in a device, the more friction and wear you will have.


 Apart from the minor detail of dramatically increased stability in both the short and long term.


> You should know better than me that in a micro-machine like watch movement the components are very sensible to wear and friction. In a two devices with a similar volume and function (e.g two three-handed watches with 2892 & 2500) the one with more parts would be more prone to problem. There would be exception only when the 2892 is poorly designed which is not the case.


 Just go back and read what CS said. The coaxial escapement is a *different *escapement. As such, it could simply be the case that the way that the coaxial escapement works could be intrinsically more reliable as well as more stable. *You simply are not comparing like with like. *If the two escapements were basically the same and handled the job the did in the same way you may have a point. However, they are not.


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## ChronoScot (Oct 25, 2010)

lvt said:


> Glad to hear from you again, CS
> 
> You said about "friction" ?
> 
> ...


Hi lvt. There are two aspects I would specifically like to address in your post - the first is the "apparent" addition of a component in the co-axial escapement, the second is the superiority (or lack thereof) of the co-axial versus the lever escapement.

You mention an additional component in the co-axial escapement, however I do not actually see this as the case, at least in terms of your argument on friction. Let us consider the main sub-assemblies of each escapement, specifically with respect to the 3 level co-ax.

The lever escapement consists of

(1) a *pallet fork/lever*
(2) a *single level escape wheel*,
(3) an *escape pinion* and
(4) a *balance wheel*.

The co-axial escapement consists of

(1) a *pallet fork/lever*,
(2) a *double level escape wheel*,
(3) an *escape pinion* and
(4) a *balance wheel*.

[Note that your drawing does not show the escape pinion and meshing with the gear train in the case of the lever escapement, which may be misleading for this comparison and leave the impression of "additional components"].

The basic sub-assemblies are therefore the same but the function and complexity of the individual sub-assemblies are of course different. The pallet fork/lever of the co-ax has three stones instead of two, the additional one serving as an additional point of impulse. The escape wheel of the co-ax has two levels, the larger wheel engaging the entrance and exit pallets (as with the lever escapement) and the smaller wheel providing impulse to the pallet fork/lever.

However to specifically address your point about friction, I count the _same number of bearing points_ in each design, therefore I see no fundamental conceptual disadvantage there. I assume that the "additional component" you refer to is the small escapement wheel, but this is mounted to the same shaft as the large escapement wheel and does not require an additional bearing point. Furthermore, the entrance and exit pallets of the co-ax engage the wheel tangentially, as opposed to sliding in the case of the lever escapement. The additional impulse pallet of the co-ax, engaging the small escapement wheel, does so tangentially. Thus, the sources of friction present in the lever escapement are minimised and/or eliminated in the case of the co-ax escapement.

I already mentioned in a separate post in this thread that, in the two level co-ax, it may be that the shape of the escape wheel teeth are not fully optimal for serving the dual function of power transmission and providing impulse to the pallet fork. This may be where the three level, separating power transmission from pallet fork impulse, brings advantages at the expense of movement thickness. But again, this does not introduce additional points of friction, the total number of functions remains the same.

Getting to the point of only paying for exclusivity and getting no superiority, the co-ax geometry and concept offers a fundamental advantage over the lever escapement, namely the escaping angle. The modern lever escapement requires an escaping angle of 53° and a total arc of 300°. The co-ax requires an escaping angle of 36° with an amplitude of 270°. The smaller escaping angle of the co-ax provides isochronal advantages i.e. stability of rate*. This is Daniels' statement, I'd suggest going through his description and extensive diagrams to satisfy yourself that this is the case if you have doubts.

Summing-up, I still cannot see the validity of your argument, namely that the co-ax reliability suffers through additional components. On the contrary, the co-ax offers isochronal benefits with a similar or lesser number of the friction sources which can contribute to failure as a result of lubricant degradation (three level co-ax). I certainly concede that the introduction of new materials in escape wheel fabrication (as Patek has done) can further optimise the sliding friction characteristic of the lever escapement, however it is not addressing the more fundamental escaping angle difference, which serves as a significant benefit for the co-ax that the leer escapement cannot come close to.

I'm interested to see your reply to this. Unfortunately I might not be able to engage fully in the next week or so, due to travel back to the home country over Christmas and New Year with limited internet access where I am staying. I will try to stay involved as much as internet access permits.

*Source: Watchmaking (2011), Gearge Daniels, pp195-246


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## lvt (Sep 15, 2009)

M4tt said:


> Apart from the minor detail that six years isn't really a Swiss Standard, it doesn't mean anything is wrong at all, the fact is that whatever the escapement may be capable of, the rest of the watch is an ordinary watch and thus slave to lubrication. Omega made a silly claim and then backtracked on it. That is all.


It's more than a silly claim, M4tt. Making you believe you have a revolutionary thing and discontinue it some years later (most of the 2500 B and C didn't even reach the 10-year interval yet), it's unfair for the end users in some way (especially those who buy Omega watches for the 1st time). Better invest the money in a watch with the 1120 or wait for the new caliber.



M4tt said:


> So oil fails due to the build up of dust? Ok...


Did I really say that ? I remember I wrote differently.



M4tt said:


> The thing is that friction in one area merely causes wear (as long as it isn't so great to reduce the available torque, while the variations in friction in the other area don't just cause friction but also cause instability due to (in the short term) things like variations in viscosity due to temperature and (in the long term) changes in viscosity and simple lack of oil.





M4tt said:


> Qua wear that may be true, qua stability it isn't due to the scraping action rather than the coaxial's rolling action.





M4tt said:


> Well, it's a bit like the 'What have the Romans ever given us sketch' The Cal.2500 offers no benefits apart from: * Due to a rolling rather than a sliding action the pallet stones do not need lubrication and friction is reduced by about 95%. obviously this removes two major areas of instability in one: variations in the sliding surface due to bedding in and variations in the oil consistency due to age and temperature. * The freesprung balance is far, far nearer to the mathematical ideal as it doesn't have a regulator interfering with the spring. This helps with all forms of stability, including, of course, positional stability. * The impulse from the pallet stones is identical in both directions, unlike every other watch on the planet. This gives a smoother more regular swing to the escapement and reduces the effects of position still further. * The escapement is in contact with the balance for a far shorter period allowing more of the balance's swing to be free of interference, once again far closer to the mathematical ideal. (this, of course, can also reduce the effect of position) * Wear on the contact surfaces of the escapement has been almost entirely eliminated. * As a net effect stability which was described by one of the UK's greatest horological statisticians as "equivalent to a marine chronometer in gimbals". But apart from that, I'm sure you are quite correct.


Please stop using the free sprung balance to impress me, M4tt, you know as well as me that a free sprung balance is not Co-ax specific, many brands use free sprung balance in their watches, Rolex is just an example with a free sprung balance.

In reality a lever escapement don't really need a free sprung balance to perform as well as the Co-ax, if not better, for example ETA movements don't need free sprung balance to be COSC certified, Seiko's GS movement don't need free sprung balance to perform better than COSC, thus better then any Co-ax movement.

The free sprung balance only changes the way to regulate a movement and it's believed to be better in long term to fight against beat error, but unless you want to leave your watch on the winder all year long and never want to adjust the watch's date and time the difference between a traditional balance and a free sprung balance is more theoretical than real perspective.



M4tt said:


> Well, as you haven't proven your case theoretically, I guess you are going to prove it empirically. Where's your evidence for this claim?


My evidence is that the lever escapement existed for hundreds of years, you can find vintage watches that still run after 50 or 60 years with very little care. We'll need another 50 years to say the same thing to the Co-ax if they are still around at that time.



M4tt said:


> Apart from the minor detail of dramatically increased stability in both the short and long term.


So do you mean other movement like Grand Seiko or Rolex 3135 are less stable than a Co-ax ? If so how it could be possible for the Grand Seiko to run better than COSC at such high beat rate if it's not stable ?

As I said earlier, the 3-tier escapement is a work-around to fix some problem (specific to the Co-ax), but adding part to the escapement might create another problem that are still unknown to date. It's like adding two additional wheels to a four-wheel vehicle, you think you would save the existing wheels from wears as the vehicle's weight is now supported by a sex-wheel setup, but actually you have more parts to maintain (tires, break, transmission...) and technically speaking the chance of failure is higher. And especially a six-wheel vehicle won't run as fast as a four-wheel because the additional wheels will create more friction and instability at high speed.

How about another example, when a vehicle needs more power the engine needs additional cylinders to increase output torque, people are aware that an Inline 6 setup is the ideal as it's more stable, lower friction, less complex, better flat torque curve at most of the time, less components needed, but it sits longer in the engine bay, so people prefer a V6 setup despite some disadvantages.



M4tt said:


> Just go back and read what CS said. The coaxial escapement is a different escapement. As such, it could simply be the case that the way that the coaxial escapement works could be intrinsically more reliable as well as more stable. You simply are not comparing like with like. If the two escapements were basically the same and handled the job the did in the same way you may have a point. However, they are not.


People compare everything, for example a Mac vs a PC as both of them receive inputs from the keyboard and display the results on the monitor. People usually by Mac for the exclusivity in design, hardware and software. So even if the lever and the Co-ax don't work the same way we still can compare them because they do the same job of keeping time.


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## M4tt (Jan 18, 2007)

> It's more than a silly claim, M4tt. Making you believe you have a revolutionary thing and discontinue it some years later (most of the 2500 B and C didn't even reach the 10-year interval yet), it's unfair for the end users in some way (especially those who buy Omega watches for the 1st time). Better invest the money in a watch with the 1120 or wait for the new caliber.


The 2500 series has been in constant production from 1999 in four marked variants. The movement has not been discontinued except in your imagination. The 1120 was in production from 1993 and developed from the 2892/2 through the 1108/1109. It has been discontinued for some time. The service cycle for the 1120 and the 2500 is identical and this has something to do with oil...


> Did I really say that ? I remember I wrote differently.


I'm sure you do; however, I quoted you in context in full before paraphrasing the key assertion.



> Please stop using the free sprung balance to impress me, M4tt, you know as well as me that a free sprung balance is not Co-ax specific, many brands use free sprung balance in their watches, Rolex is just an example with a free sprung balance.


The difference is that, for levers, the weakest link is the escapement and, for the coaxial, the weakest link is the balance. The FSB makes a significant difference to the coaxial and very little to a lever - the lever is the problem, not the balance.



> In reality a lever escapement don't really need a free sprung balance to perform as well as the Co-ax, if not better, for example ETA movements don't need free sprung balance to be COSC certified, Seiko's GS movement don't need free sprung balance to perform better than COSC, thus better then any Co-ax movement.


I think you are confusing the actual performance with the testing regime. The map is not the territory. COSC is easy to pass for pretty well any carefully set up modern movement. The coaxial is invariably far more stable than is ever needed to pass COSC but Omega only regulate to pass COSC as it saves them the cost of someone finely regulating the watch. 


> The free sprung balance only changes the way to regulate a movement and it's believed to be better in long term to fight against beat error,


So having a spring that is fixed at two ends and has no interference along its length is exactly the same as a spring that is fixed at two ends and then regulated by interfering with the dynamics of the spring (by passing the spring through two teeth that allow you to vary the length of the spring). One is regulated by changing the dynamics of the *balance *and one by changing the dynamics of the *spring*. Have a think about how easy it isn't to precisely poise a spring, think about how much easier it isn't to precisely poise a spring that is being messed about with by a movable yoke. 


> but unless you want to leave your watch on the winder all year long and never want to adjust the watch's date and time the difference between a traditional balance and a free sprung balance is more theoretical than real perspective.


So you concede that the coaxial escapement is far more stable, but just don't think that precise timekeeping matters?



> So do you mean other movement like Grand Seiko or Rolex 3135 are less stable than a Co-ax ? If so how it could be possible for the Grand Seiko to run better than COSC at such high beat rate if it's not stable ?


Yes, all things being equal, they will be less stable. However, the GS spec is one that the coaxial could pass more easily than the GS passes it. I didn't say it's not stable, merely that it isn't as stable. The GS takes the leer about as far as it can go. The coax is in a different league. 


> As I said earlier, the 3-tier escapement is a work-around to fix some problem (specific to the Co-ax), but adding part to the escapement might create another problem that are still unknown to date.


How can you know that? Care to share your source or is this just your inspired guess (again). Omega say that it is merely to bring the two movement families into line. I'm sure you know better. As for causing another problem, I think that the cog and wheel set up is pretty familiar territory for a watch company, so I doubt it.



> It's like adding two additional wheels to a four-wheel vehicle, you think you would save the existing wheels from wears as the vehicle's weight is now supported by a sex-wheel setup, but actually you have more parts to maintain (tires, break, transmission...) and technically speaking the chance of failure is higher. And especially a six-wheel vehicle won't run as fast as a four-wheel because the additional wheels will create more friction and instability at high speed.


I believe that CS has proven this assertion to be nonsense. Even if he hadn't, this is not a convincing metaphor.



> How about another example, when a vehicle needs more power the engine needs additional cylinders to increase output torque, people are aware that an Inline 6 setup is the ideal as it's more stable, lower friction, less complex, better flat torque curve at most of the time, less  components needed, but it sits longer in the engine bay, so people prefer a V6 setup despite some disadvantages.


Yes, the three tier setup should be thicker, but somehow Omega have fitted it into the available space.Clever Omega.



> People compare everything, for example a Mac vs a PC as both of them receive inputs from the keyboard and display the results on the monitor. People usually by Mac for the exclusivity in design, hardware and software. So even if the lever and the Co-ax don't work the same way we still can compare them because they do the same job of keeping time.


Actually, the comparison between CLI and GUI is a perfect example: when the Mac first came out, it also had a thing called a *mouse*, and a unique graphic interface 'borrowed' from the ZEROX PARC approach to Human Computer Interaction. The two simply were not comparable because the graphical user interface was so superior to the command line interface. Now *almost everyone *has stolen that approach and CLIs tend only to be used for specialised interfaces or as a backup. Maybe that is what will happen to the coaxial - it's so much better that everyone will use it.

Now I have to go and baste two ducks and make excuses for hiding for twenty minutes. Enjoy your festivities all.


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## lvt (Sep 15, 2009)

ChronoScot said:


> Hi lvt. There are two aspects I would specifically like to address in your post - the first is the "apparent" addition of a component in the co-axial escapement, the second is the superiority (or lack thereof) of the co-axial versus the lever escapement.
> 
> You mention an additional component in the co-axial escapement, however I do not actually see this as the case, at least in terms of your argument on friction. Let us consider the main sub-assemblies of each escapement, specifically with respect to the 3 level co-ax.
> 
> ...


Hi CS,

There is problem with your listing, the Co-axial escapement clearly has an intermediate wheel.

More wheel / component mean more physical contact, bearing... actually the following components are required in the Co-ax but don't exist on the lever :

1 - an additional pallet-stone.
2 - an additional wheel to form a double escape wheel (or Co-ax wheel).
3 - an additional intermediate wheel.

Please reconsider your listing before entry further in the details.

About the gear train meshing, I don't see any misleading or hidden detail, on the lever the escape wheel is the last wheel on the gear train, however on the Co-ax the last wheel in the gear train is the intermediate wheel.

If you preferthe new 3-tier instead of the old Co-ax design I will include a photo, it's even better to see what I say above with this photo of the real thing :


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## lvt (Sep 15, 2009)

I'm still perplexed about the new 3-tier design, we all know that the Co-ax is designed to reduce friction on the escapement but I wonder what would be the final result once you added a lot of components, especially the additional gear meshing on top of the Co-ax wheel, it might be a new weak point of the whole escapement if you don't lubricate it properly or if the oil is dried...

My guess is that the 3-tier is designed to solve the problem on the old Co-ax while sacrifying a lot of what the old Co-ax was initially designed for, the end result might be a more stable Co-ax escapement, capable of running at higher speed but with shorter service interval due to the complexity and special technical aspects of its design.

I think it would be a wonderful idea if Omega puts a lever escapement on a 8500 or a 9300 and sell them for other brands, the annual calendar and the column wheel chronograph are great complications, they shouldn't be comdemned to only work with the Co-ax escapement.


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## M4tt (Jan 18, 2007)

> I'm still perplexed about the new 3-tier design, we all know that the Co-ax is designed to reduce friction on the escapement but I wonder what would be the final result once you added a lot of components, especially the additional gear meshing on top of the Co-ax wheel, it might be a new weak point of the whole escapement if you don't lubricate it properly or if the oil is dried...


there was a single part doing three jobs in three places now there is a single part doing three jobs in three places. All that has happened is that the places have been rationalised. 


> My guess is that the 3-tier is designed to solve the problem on the old Co-ax while sacrifying a lot of what the old Co-ax was initially designed for, the end result might be a more stable Co-ax escapement, capable of running at higher speed but with shorter service interval due to the complexity and special technical aspects of its design.


Your guess is wrong. Why it is wrong has already been explained.



> I think it would be a wonderful idea if Omega puts a lever escapement on a 8500 or a 9300


Why? They'd make them less stable _and _less interesting in one fell swoop.



> and sell them for other brands,


Why would you want Omega to do this? what possible advantage would it have for Omega or Omega owners?



> the annual calendar and the column wheel chronograph are great complications, they shouldn't be comdemned to only work with the Co-ax escapement.


That's fine, at least one of these complications is available in very cheap Chinese watches (Tianjin St19) (and the other probably is and is certainly available in other Swiss brands).


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## M4tt (Jan 18, 2007)

I think perhaps there has been a misunderstanding here. I certainly thought the discussion was of the escapement, not of the whole ebauche. Yes, the coaxial has one extra wheel in the train, but this plays no additional role in the interaction of the balance and escapement beyond powering it: if you are going to say that this intermediary wheel is part of the escapement then you would have to say it of the fourth wheel, third wheel, centre wheel and ultimately of the mainspring. 

Now I know that you are going to assert that this automatically means that the unit as a whole will be less reliable. However, as explained ad nauseum, this might be true if all other factors were equal and the wheels were powering the same escapement, but they are not: all things are not equal.


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## lvt (Sep 15, 2009)

M4tt said:


> That's fine, at least one of these complications is available in very cheap Chinese watches (Tianjin St19) (and the other probably is and is certainly available in other Swiss brands).


I owned a Seagull (or Tianjin) ST-19 based watch in the past, yes the ST-19 is a column wheel driven chronograph but it's different from the Omega's 9300 (the ST-19 is a simple 30 min. chronograph).

And the ST-19 beats at only 21,600bph while the 9300 beats at 28,800bph.

Hope you see the difference.


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## Archer (Apr 23, 2009)

M4tt said:


> I think perhaps there has been a misunderstanding here. I certainly thought the discussion was of the escapement, not of the whole ebauche. Yes, the coaxial has one extra wheel in the train, but this plays no additional role in the interaction of the balance and escapement beyond powering it: if you are going to say that this intermediary wheel is part of the escapement then you would have to say it of the fourth wheel, third wheel, centre wheel and ultimately of the mainspring.
> 
> Now I know that you are going to assert that this automatically means that the unit as a whole will be less reliable. However, as explained ad nauseum, this might be true if all other factors were equal and the wheels were powering the same escapement, but they are not: all things are not equal.


A traditional lever escapement consists of the impulse pin (roller jewel) as the balance wheel and spring are not considered part of the escapement, the pallet fork, and the escape wheel.

Omega calls the extra wheel the "Intermediate Escape Wheel" in the technical guide. If you look at this page on their web site: OMEGA Watches: How it works

It says this:

"The OMEGA Co-Axial escapement consists of an intermediary wheel, a double coaxial wheel consisting of an escapement pinion and an escapement wheel, a lever with three ruby pallet-stones and a roller carrying a ruby impulse stone and a ruby impulse pin."

It seems Omega considers this as part of the escapement, which means indeed the co-axial escapement has more parts than a traditional lever escapement does. Whether or not this is significant? I'll let you guys battle that out. 

Cheers, Al


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## lvt (Sep 15, 2009)

M4tt said:


> Why? They'd make them less stable _and _less interesting in one fell swoop.


Why a lever escapement would make them less stable ? How about one from Rolex or IWC ?

Why a lever escapement would make them less interesting ? With a lever the 9300 could beat at 36,000bph like an El Primero, isn't it interesting ?


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## ChronoScot (Oct 25, 2010)

lvt said:


> Hi CS,
> 
> There is problem with your listing, the Co-axial escapement clearly has an intermediate wheel.
> 
> ...


lvt, you argued that (a) the co-axial escapement is less reliable than a lever escapement by virtue of a larger number of components and (b) the increased number of friction points associated with these additional components was a driver for this reduced reliablity.

The co-ax escapement (both the three-tier and two-tier variants) has the same number of meshing pairs as a lever escapement. These are:


Escape pinion to the wheel train (three-tier) _or_ small escape wheel to the wheel train (two tier) 
Escape wheel to the pallet fork 

The difference is of course that the escape wheel of the co-ax meshes with three pallets (one of the additional components you have listed), whereas the escape wheel of the lever escapement meshes with only two. However there are several aspects of this critical difference that make it over-simplistic to make statements on reliability based on the number of components, as the functionalities of the comparable parts differ.

Co-Ax
The entry and exit pallets of the co-ax pallet fork are there to stop the motion of the escape wheel. They engage tangentially with the large wheel, with minimal friction. The middle pallet receives an impulse from the small escape wheel, also tangentially and with minimum friction. The large escapement wheel furthermore provides an impulse directly to the balance.

Lever
The entry and exit pallets serve the functions of stopping the motion of the escape wheel _and_ receiving impulses, which are transmitted to the balance wheel. The critical difference is that these impulses are imparted through sliding friction instead of tangentially.​
So although there are three points of engagement through the additional pallet on the pallet fork, this does not qualitatively result in an additional friction point. It is a very novel approach to separate a number of functions over several sub-components and benefit from a geometry that in fact reduces friction through tangential impulses and start/stop engagement instead of combining the start/stop engagement and impulses on the same pallets, resulting in sliding friction.

Furthermore, the number of pivot points is the same between both escapements. While the escape wheel of the co-ax can indeed be disassembled into two individual wheels and (in the case of the three-tier variant) and escape pinion, they rotate on _one_ bearing. The large wheel on the left of your illustration is part of the wheel train and is common to movements containing the lever escapement. Thus, no additional friction points in this respect either.

However this whole argumentation even becomes somewhat moot when the escaping angle is considered, which I raised in my previous post and you did not respond to. The differing geometry of the co-ax, involving additional components (but _not_ additional functional sub-systems) results in a setup where the escapement interferes with the balance wheel for a smaller proportion of its total arc of rotation than the lever escapement. This provides fundamental isochronal benefits. Now I am not trying to maintain that the isochronal performance of any co-ax escapement is superior to any and all lever escapements, as they can both be adjusted/regulated to a high degree of accuracy and meet/exceed COSC and more stringent requirements. However the co-ax is going to be on average more robust due to the reduced interference with the balance and the fact that it has _less_ sources of friction and not more, as you have maintained.

To sum up again:


A co-ax escapement has the same number of functional sub-systems as a lever escapement, however the number of individual components differ 
The higher number of components in the co-ax cannot be used as a measure of reliablity versus the lever escapement, as they perform different respective sub-functions 
The splitting up of these sub-functions in the co-ax and associated geometry results in minimised sources of friction and lesser interference with the balance wheel through a smaller escaping angle, serving to improve the isochronal robustness of the co-ax versus the lever escapement 

I'll add some points on the differences between the three-tier and two-tier variants in response to your other post.


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## suparobg (Nov 2, 2009)

I sent Omega customer service an email several years ago to inquire which 2500 movement was in my 42mm PO. They wrote back that my serial number was fitted with the 2500 A movement. on another note it has been running flawlessly for the past 5 + years now

Dear Mr Gergely, 

We thank you for your new e-mail and would like to inform you that your OMEGA watch serial no 80918--- is fitted with a movement caliber 2500A. 

With kind regards,

Maria Mastrodonato
INTERNATIONAL CUSTOMER CARE

*Ω OMEGA SA*
RUE STÄMPFLI 96
2500 BIENNE 4
SWITZERLAND
[email protected]
www.omegawatches.com


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## suparobg (Nov 2, 2009)

I sent Omega customer service an email several years ago to inquire which 2500 movement was in my 42mm PO. They wrote back that my serial number was fitted with the 2500 A movement. on another note it has been running flawlessly for the past 5 + years now

Dear Mr Gergely,

We thank you for your new e-mail and would like to inform you that your OMEGA watch serial no 80918--- is fitted with a movement caliber 2500A. 

With kind regards,

Maria Mastrodonato
INTERNATIONAL CUSTOMER CARE

*Ω OMEGA SA*
RUE STÄMPFLI 96
2500 BIENNE 4
SWITZERLAND
[email protected]
www.omegawatches.com


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## ChronoScot (Oct 25, 2010)

lvt said:


> I'm still perplexed about the new 3-tier design, we all know that the Co-ax is designed to reduce friction on the escapement but I wonder what would be the final result once you added a lot of components, especially the additional gear meshing on top of the Co-ax wheel, it might be a new weak point of the whole escapement if you don't lubricate it properly or if the oil is dried...
> 
> My guess is that the 3-tier is designed to solve the problem on the old Co-ax while sacrifying a lot of what the old Co-ax was initially designed for, the end result might be a more stable Co-ax escapement, capable of running at higher speed but with shorter service interval due to the complexity and special technical aspects of its design.
> 
> I think it would be a wonderful idea if Omega puts a lever escapement on a 8500 or a 9300 and sell them for other brands, the annual calendar and the column wheel chronograph are great complications, they shouldn't be comdemned to only work with the Co-ax escapement.


lvt, have a look at my previous post, with extracts from Daniels' Watchmaking book, which I've pasted below. If I'm not mistaken, the three tier variant of the co-ax escapement is in fact Daniels' "original". He calls what we describe as the two-tier version, i.e. cal 2500C, the "Extra Flat Co-Axial Escapement", designed for thin watches. This eliminates the escape pinion and incorporates the escape pinion functionality into the small escapement wheel (which also provides impulses to the balance wheel).

I believe that Omega wanted to use this variant in their co-ax movements to avoid having to build very thick watches (such as the ones we see today with the cal 85xx and cal 93xx ranges) and thus developed/incorporated it in the beginning during the collaboration with Daniels. I think that the feedback that came from mass producing this version caused them to re-think the robustness of the dual functionality of the small escape wheel. Recall that Daniels watches were all hand built and limited in number, therefore he did not have the benefit of such feedback when proposing designs and variants to Omega. This re-think by Omega resulted first in the use of a three-tier escapement in the cal 85xx, followed by the update of the cal 2500 3-4 years later.

I think that Omega has taken a decision to have a more robust and simple solution (the three tier) at the expense of a thicker movement. Many of my posts show that I am a strong proponent of co-axial escapement technology, however I do see this as a drawback with respect to the lever escapement. But as I have stated many times now, I see very concrete reasons for the co-axial escapement being the more (isochronally) robust solution.



ChronoScot said:


> Hi Matt. Yes, I agree. The replacement of a component which serves two distinct functions with two separate components, each of which is optimised for one of the two functions, can result in a more reliable arrangement than the original situation, in spite of the apparent increase in complexity to the casual observer.
> 
> This is particularly the case with respect to gear transmission, for which the shapes of gear teeth and pinion leaves are optimised to ensure that the direction of the transmitted force is perpendicular to the point of contact at the mid-point of the motion as well as to minimise power transmission losses before and after this point*. It becomes a challenge to define the shape of the small escapement wheel teeth to optimally perform the dual function of impulsing a pallet and transmitting power from the gear train.
> 
> ...


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## M4tt (Jan 18, 2007)

> It seems Omega considers this as part of the escapement, which means indeed the co-axial escapement has more parts than a traditional lever escapement does. Whether or not this is significant? I'll let you guys battle that out.


I know Omega do, but you will note that I didn't assert that it _was_. I put forward a conditional argument: 


> *if *you are going to say that this intermediary wheel is part of the escapement *then *you would have to say it of the fourth wheel, third wheel, centre wheel and ultimately of the mainspring.


So if we accept Omega's assertion that the intermediary wheel is part of the escapement, do we accept that the fourth wheel is part of the escapement for the lever? If we do not then why are we treating two parts with the same functional role differently? Why is one considered part of the escapement and one not?

To be honest, I was defending Chronoscot's excellent analysis of the escapement and noted that he acknowledged that the picture of the lever didn't include the:



> ...meshing with the gear train in the case of the lever escapement, which may be misleading for this comparison and leave the impression of "additional components"


A point which he returns to again here: 


> The large wheel on the left of your illustration is part of the wheel train and is common to movements containing the lever escapement. Thus, no additional friction points in this respect either.


As such, I thought it was clear that CS was focussing on the escapement rather than the train. That was the context of my observation that they there had been a misunderstanding.

In short, I doubt that chronoscot is unaware of the amount of wheels in the two trains.


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## M4tt (Jan 18, 2007)

> I sent Omega customer service an email several years ago to inquire which 2500 movement was in my 42mm PO. They wrote back that my serial number was fitted with the 2500 A movement. on another note it has been running flawlessly for the past 5 + years now
> 
> Dear Mr Gergely,
> 
> ...


They are wrong. The PO wasn't even a gleam in Hayek's eye when the 2500A was discontinued.


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## mark.altern (Jan 26, 2011)

ChronoScot said:


> I believe that Omega wanted to use this variant in their co-ax movements to avoid having to build very thick watches (such as the ones we see today with the cal 85xx and cal 93xx ranges) and thus developed/incorporated it in the beginning during the collaboration with Daniels. I think that the feedback that came from mass producing this version caused them to re-think the robustness of the dual functionality of the small escape wheel. Recall that Daniels watches were all hand built and limited in number, therefore he did not have the benefit of such feedback when proposing designs and variants to Omega. This re-think by Omega resulted first in the use of a three-tier escapement in the cal 85xx, followed by the update of the cal 2500 3-4 years later.


Hi Chrono, if your speculation is right, then 2500D solves both unreliability problems in previous generation and the thicknes issue, however, Omege still implement 8500 in its new PO line, instead of continuing using 2500D, despite the thickness of 8500. I guess, 8500 got to have something really superior than 2500D, i.e. not just 60 power serve.

While saying that, I hope not to open another can of worms ;-)


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## Archer (Apr 23, 2009)

M4tt said:


> I know Omega do, but you will note that I didn't assert that it _was_. I put forward a conditional argument:
> 
> So if we accept Omega's assertion that the intermediary wheel is part of the escapement, do we accept that the fourth wheel is part of the escapement for the lever? If we do not then why are we treating two parts with the same functional role differently? Why is one considered part of the escapement and one not?
> 
> ...


Okay - taking a break from my 3rd watch of the day to answer this - briefly.
Matt - call it what you like - train or esacapement part (BTW in Omega's terms there is no 4th wheel). The fact is that this wheel is required because of the co-axial escapement. It's not there in the Cal. 1120 version of the movement, so whatever you choose to call it, it's not simply another "regular" train wheel in my view. 

The point that I think is relevant is whether or not this part makes a difference to the reliability of the movement. In this case it has in the past. If you recall our previous discussions, this is the wheel that Omega was seeing the black residue on, and was replacing with a wheel that was coated differently. So it has had an impact on the reliability of the movement. Will it in the future? Time will tell.

Cheers, Al


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## M4tt (Jan 18, 2007)

> Okay - taking a break from my 3rd watch of the day to answer this - briefly.
> Matt - call it what you like - train or esacapement part (BTW in Omega's terms there is no 4th wheel). The fact is that this wheel is required because of the co-axial escapement. It's not there in the Cal. 1120 version of the movement, so whatever you choose to call it, it's not simply another "regular" train wheel in my view.


Yes, that makes more sense than the way I am approaching it.



> The point that I think is relevant is whether or not this part makes a difference to the reliability of the movement. In this case it has in the past. If you recall our previous discussions, this is the wheel that Omega was seeing the black residue on, and was replacing with a wheel that was coated differently. So it has had an impact on the reliability of the movement. Will it in the future? Time will tell.


Yes, again, I am focusing on the semantics while ignoring the more important question; 'In practice' generally trumps 'in theory'. (although I'd still like to know what is going on there...)

Cheers Archer, I'd got that all the wrong way around. Thanks for taking he time to explain it clearly.


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## ChronoScot (Oct 25, 2010)

Archer said:


> Okay - taking a break from my 3rd watch of the day to answer this - briefly.
> Matt - call it what you like - train or esacapement part (BTW in Omega's terms there is no 4th wheel). The fact is that this wheel is required because of the co-axial escapement. It's not there in the Cal. 1120 version of the movement, so whatever you choose to call it, it's not simply another "regular" train wheel in my view.
> 
> The point that I think is relevant is whether or not this part makes a difference to the reliability of the movement. In this case it has in the past. If you recall our previous discussions, this is the wheel that Omega was seeing the black residue on, and was replacing with a wheel that was coated differently. So it has had an impact on the reliability of the movement. Will it in the future? Time will tell.
> ...


Thanks Al for pointing that out.

Indeed as Matt has suggested, I am trying to directly compare the co-axial escapement with the lever escapement, which in my comparison ends at the output from the escape wheel shaft.

If we compare directly the 2500C with the 1120, we will see that the number of teeth on the respective escape wheels differ. The 2500C has an 8 tooth escape wheel. The 1120 has a 20 tooth escape wheel. This means of course that for a given number of vibrations per hour (not to mention for now that the number of vibrations per hour does also differ between the movements), the rotational rate of the output shaft will be different between the two escapements. Thus, modifying a lever escapement ebauche with 20 teeth on the escape wheel (1120) with a co-ax escapement having 8 teeth will necessitate adjustement of the gear ratios in the train so that the hands continue to advance at the correct rate (the important bit).

I believe that Omega have retained the same second and third wheel between the 1120 and the 2500C, and adjusted the total gear ratio by adding the so-called "intermediate escape wheel", as an alternative to adjusting all of the wheels in the train (at which point it would start to seriously deviate from being a 1120 ebauche with modified escapement). I am also interested to see (if it ever comes to light) whether driving the train through a pinion which is separate from the small escape wheel (2500D) would reduce or eliminate the black residue you mention.

Now addressing lvt's arguments, I would hope that his compelling point about relative complexity and number of parts favouring the lever over the co-ax is _not_ that, since Omega have added a wheel in the train using the name "intermediate escape wheel" to adjust the gear ratios necessary for a smaller escape wheel to be added to an existing ebauche, the co-ax escapement can be considered more complex and less reliable. This would be in my opinion attacking a straw man.

For purposes of comparison, I consider the output of two escapement to be the shaft which connects to the rest of the train i.e. the shaft carrying the escape wheel and escape pinion. I would still like to hear lvt's response to the fact that the co-ax enables a smaller escaping angle (better isochronal robustness) while splitting the start/stop and impulse functions over three pallets (instead of two) and a two level escape wheel (instead of single level) to enable minimised friction through tangential instead of sliding contact.


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## ChronoScot (Oct 25, 2010)

mark.altern said:


> Hi Chrono, if your speculation is right, then 2500D solves both unreliability problems in previous generation and the thicknes issue, however, Omege still implement 8500 in its new PO line, instead of continuing using 2500D, despite the thickness of 8500. I guess, 8500 got to have something really superior than 2500D, i.e. not just 60 power serve.
> 
> While saying that, I hope not to open another can of worms ;-)


That's a very good point Mark.

Based on the technical manuals, the cal 1120A has a thickness of 4.00mm and the cal 2500C a thickness of 4.10mm. The cal 8500 is an impressive 5.50mm thick. The missing information is the thickness of the the cal 2500D. Since its introduction went largely unnoticed until new date fonts and COSC certificate entries were highlighted, one could speculate that the thickness is the same as the cal 2500C, given that 1st gen Planet Ocean cases have apparently not become thicker.

This consideration does go against my argument somewhat. Now I'm also wondering if the three tier escapement is the only design consideration driving the thickness of the new 85xx and 93xx movements.


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## ChronoScot (Oct 25, 2010)

ChronoScot said:


> Thanks Al for pointing that out.
> 
> Indeed as Matt has suggested, I am trying to directly compare the co-axial escapement with the lever escapement, which in my comparison ends at the output from the escape wheel shaft.
> 
> ...


We can take the discussion of this intermediate escapement wheel a little further still with respect to lvt's position on additional components leading to reduced reliability of the co-axial escapement.

Let me concede _for the moment_ (for the purposes of discussion) that the intermediate escape wheel would be a necessary addition when fitting a given watch with a co-axial escapement instead of a lever escapement, and that it is not just there to balance out the need for a different gear ratio (due to the differently sized escape wheel) with the avoidance of resizing the entire train. If this would be the case, then I would call the output of the co-axial escapement the shaft of this intermediate wheel, whereas the output of the lever escapement is the shaft of the escape wheel.

Coming back to my comparison of functional sub-systems, we would have the respective escapements consisting of the following:

Lever escapement

(1) a *pallet fork/lever*
(2) a *single level escape wheel*,
(3) an *escape pinion* and
(4) a *balance wheel*

 Co-axial escapement

(1) a *pallet fork/lever*,
(2) a *double level escape wheel*,
(3) an *escape pinion*
(4) a *balance wheel* and
(5) an *intermediate escapement wheel

*Now, if the elements 1-4 between the two escapements would have the same mean failure rate, then the addition of element 5 to the co-axial escapement would render it mathematically impossible for the reliability to be higher than the lever escapement (if you go to sufficient decimal places, as the difference will be tiny and measured in years). But this is exactly where lvt's argument fails, because elements 1-4 are _not_ the same and perform their functions in different ways.

The use of a double escape wheel and pallet fork having three pallets enables a geometry which results in tangential (practically friction free) start/stop of the escape wheel and impulses to the balance wheel. Furthermore, this geometry reduces the escaping angle, effectively shortening the length of the arc over which the escapement is interfering with the oscillation of the balance spring.

I would therefore contend that elements 1-4 of the co-axial escapement are in fact _more_ reliable than corresponding elements of the lever escapement, and that they provide on top of this a more robust isochronal performance. I would not necessarily argue this for the two tier co-axial escapement, as the small escapement wheel has a dual function which could be comprimised by incorrect lubrication of the teeth e.g. causing a black residue to build up, such as that highlighted by Al, leading to a potential stop of the movement. I would contend that the separation of these functions in the three tier variant would in fact, while adding a further sub-component, lead to a more robust design.

So even if the intermediate escape wheel is considered an integral part of the co-axial escapement, I still see very strong qualitative reasons for the co-axial escapement being the fundamentally more robust concept, both in terms of not breaking down and accurately showing the time.


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## Shane (Qld) (Feb 26, 2012)

So in laymans terms is the 2500D a better design over the "C", but is yet unproven in regards to reliabiliy long term. If the "D" is a better design in the 2500 & a precurser to the new model why is the 8500 a thicker design & the improved 2500 no longer used in the PO.


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## M4tt (Jan 18, 2007)

> So in laymans terms is the 2500D a better design over the "C"


No, it's an almost identical design, but has changed the way that power is delivered to the coaxial wheel. Whether this is better or not is really difficult to be sure about. Certainly it appears to sidestep one potential issue, but it will be interesting to see if this actually makes any difference in the long run.



> but is yet unproven in regards to reliabiliy long term.


Precisely; while cogs are a well known commodity, complex parts that are so small they need a new manufacturing technique to be viable, well who knows? Omega clearly think so...



> If the "D" is a better design in the 2500


If...


> & a precurser to the new model


Where did you get that idea (and if the answer is LVT then I have written 'gullible' on your ceiling above your head!)


> why is the 8500 a thicker design


Because it is a completely different movement which happens to share a similar design of escapement. 


> the improved 2500 no longer used in the PO.


Because it was thick enough to handle it and allows Omega to charge lots more for a a movement that costs very little more to make. Stick the 8500 in the SeMP and it would ruin its svelt lines.


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## Shane (Qld) (Feb 26, 2012)

Thank's for the info M4tt, explains the technical jargon of the Watchmaker in more simplified terms to the not so minded serfs ! As much as the new 8500 is nice, I am not in favour of it's thickness & obviously more weight and chose the 2500 in preference after trying on both. When looking at the general appearance of the two together I thought the older model was a nicer looking watch & not looking like a pumpkin on a mole hill on the wrist. It seemed to conform to the arm in a more unified way. (No disrespect to existing owners of the 8500, as this is only a personel thing !).


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## M4tt (Jan 18, 2007)

> Thank's for the info M4tt, explains the technical jargon of the Watchmaker in more simplified terms to the not so minded serfs ! As much as the new 8500 is nice, I am not in favour of it's thickness & obviously more weight and chose the 2500 in preference after trying on both. When looking at the general appearance of the two together I thought the older model was a nicer looking watch & not looking like a pumpkin on a mole hill on the wrist. It seemed to conform to the arm in a more unified way. (No disrespect to existing owners of the 8500, as this is only a personel thing !).


I do worry that the 8500 is a bit too thick for a fair few applications and that the fact that the PO had to be deeper to fit it is a concern in the longer term. I worry that the molehill will have a few more pumpkins on it in time. (and that made me smile!)


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## Vertec (Feb 28, 2012)

This thread did clear up a few questions I had about the beat rate of the 8500 and 9300. 

Now I am feeling like I don't want Omega to increase the beat rate of the 8500 to 28,800 vph. I know how many of you out there seem to think that is an ideal rate but if it means longer life and less service is required, I am all for keeping it lower. 

Much like an engine, more revolutions means more wear. While technically a high beat rate is impressive, I would much prefer reliability.


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## aardvarkbark (Oct 27, 2010)

Shane (Qld) said:


> As much as the new 8500 is nice, I am not in favour of it's thickness & obviously more weight and chose the 2500 in preference after trying on both. When looking at the general appearance of the two together I thought the older model was a nicer looking watch & not looking like a pumpkin on a mole hill on the wrist.


'Pumpkin on a molehill'?? What a peculiar metaphor. Or is it simile. I know I missed those questions on the SAT. Funny visual though.

But if the 8500 PO is one, I wonder what the 2cm thick Z-33 should be labeled....


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## Knoc (Feb 10, 2012)

aardvarkbark said:


> 'Pumpkin on a molehill'?? What a peculiar metaphor. Or is it simile. I know I missed those questions on the SAT. Funny visual though.
> 
> But if the 8500 PO is one, I wonder what the 2cm thick Z-33 should be labeled....


Bulletproof.


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## Shane (Qld) (Feb 26, 2012)

aardvarkbark said:


> 'Pumpkin on a molehill'?? What a peculiar metaphor. Or is it simile. I know I missed those questions on the SAT. Funny visual though.
> 
> But if the 8500 PO is one, I wonder what the 2cm thick Z-33 should be labeled....


Being a gentleman I didn't want to say it "stood out like a sh-t house in the middle of a paddock" Unquote.


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## GaryF (Dec 18, 2009)

Shane (Qld) said:


> Being a gentleman I didn't want to say it "stood out like a sh-t house in the middle of a paddock" Unquote.


Turd on a Birthday cake. 
Any more?


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## GaryF (Dec 18, 2009)

M4tt said:


> I do worry that the 8500 is a bit too thick for a fair few applications and that the fact that the PO had to be deeper to fit it is a concern in the longer term. I worry that the molehill will have a few more pumpkins on it in time. (and that made me smile!)


I agree. With the HV and the AT, the effect of the dimensions wasn't really obvious but, with the PO, the potential for issues has been made a little more clear. Rolex has come late to the Big Watch party but, with the new escapements, Omega has bought shares in it. As I've said before, I really worry that Omega have committed themselves to path that is leading in a direction that many others in the industry are turning away from. 
I see that they have 45mm+ Speedmasters on next year's release list. It feels like someone replacing all of their old trousers with flares in 1978.


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## lhawli (Jan 24, 2016)

I have an Omega PO 45.5 cal 2500D and I wish I had the same model and caliber only in a 42.

Here's where I am looking for advise. I found one PO 42 never serviced yet and purchased in 2011. It has cal 2500C though! Since 2011 is has been running fine, but assume naturally it is due for service anytime soon. I don't want 2 - I would probably want to sell mine, which was purchased in 2012 and never serviced.

In all your opinions, given that I really want the 42 instead, would you take a "risk" (if any) to go from rev D to C?


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## DocJekl (May 19, 2014)

Lamz said:


> I have an Omega PO 45.5 cal 2500D and I wish I had the same model and caliber only in a 42.
> 
> Here's where I am looking for advise. I found one PO 42 never serviced yet and purchased in 2011. It has cal 2500C though! Since 2011 is has been running fine, but assume naturally it is due for service anytime soon. I don't want 2 - I would probably want to sell mine, which was purchased in 2012 and never serviced.
> 
> In all your opinions, given that I really want the 42 instead, would you take a "risk" (if any) to go from rev D to C?


In my case I've had the stoppage issue with the 2500C in my 2009 Planet Ocean in 2014 (5 years old), and I would stick with the 2500D if I was you. However that did not stop me from buying another 2500C, although it was a Planet Ocean Liquid Metal Limited Edition sold in April 2011 via an AD and well worth the compromise.

Unless the 45.5 looks silly big on your wrist I'd stick with it, although I wouldn't rule out adding something else to it. Maybe have both but do a bezel swap so one is black and one is orange? Even better, the 42mm PO 8500 Liquid Metal wears as nicely as my 42mm PO 2500 due to the diet it went on with the lighter Titanium, and it's stunning to look at in real life (better than a Rolex Hulk).


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## lhawli (Jan 24, 2016)

Thanks larryganz.

I wouldn't want 2 PO's to be honest, especially when I have a SubC also. If anything I would opt for the new speedy '57 broad arrow with the vintage dial look if I want to own two Omega watches.

I'm contemplating for now, but would like to see what surprise we getting from the baselworld 2016.

As for the PO 8500, I love it, no I really love it, just can't handle the thickness! The 42 I tried on wears small on my wrist given the thickness of the watch. The PO 2500 in 42 is the perfect combination and wears beautifully - a rugged diver with a more classic size.

Thanks for your advice


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## mjoranga (Jul 19, 2015)

Some great information to learn about this 2500 movement...


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## GTTIME (Jun 28, 2009)

mjoranga said:


> Some great information to learn about this 2500 movement...


You can favorite a thread rather than necro a thread and clog up the forum with your bookmarking.


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## mjoranga (Jul 19, 2015)

GTTIME said:


> You can favorite a thread rather than necro a thread and clog up the forum with your bookmarking.


Apologies Mate, didn't managed to figure it out as I'm out and was rushing to save it for a later read. Thanks for the tips, will keep that in mind.😊

Sent from my SM-G900F using Tapatalk


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## MikeCfromLI (Jan 6, 2012)

DocJekl said:


> In my case I've had the stoppage issue with the 2500C in my 2009 Planet Ocean in 2014 (5 years old), and I would stick with the 2500D if I was you. However that did not stop me from buying another 2500C, although it was a Planet Ocean Liquid Metal Limited Edition sold in April 2011 via an AD and well worth the compromise.
> 
> Unless the 45.5 looks silly big on your wrist I'd stick with it, although I wouldn't rule out adding something else to it. Maybe have both but do a bezel swap so one is black and one is orange? Even better, the 42mm PO 8500 Liquid Metal wears as nicely as my 42mm PO 2500 due to the diet it went on with the lighter Titanium, and it's stunning to look at in real life (better than a Rolex Hulk).


I had the stoppage issue on a C but it was due service anyway and I am completely confident it will be perfectly fine when it comes back from service.

M









Sent from my iPad using Tapatalk


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## mjoranga (Jul 19, 2015)

Well, I've managed to read most of the important parts and enjoyed the discussion between Al and M4tt... Al confirmed that my watch is indeed a 2500c and since Omega serviced it last Dec. 2015. I guess I don't need to worry for the next 3 to 4 more years. One thing I've noticed between my 2254 and 2500PO is that, My 2500 PO will start straight away out of the Box from the moment I shake it, while the 2254 needs a little more shaking off. Accuracy wise, they are neck and neck as I've managed to figure it out what's the best position when they are resting at night.


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## Vlciudoli (Feb 24, 2013)

GTTIME said:


> You can favorite a thread rather than necro a thread and clog up the forum with your bookmarking.


.... a bit harsh.....


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## GTTIME (Jun 28, 2009)

Vlciudoli said:


> .... a bit harsh.....


It wasn't intended to be harsh nor do I think it was. There were at least two threads which it was done at the same time. So I made the comment.


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## mjoranga (Jul 19, 2015)

GTTIME said:


> It wasn't intended to be harsh nor do I think it was. There were at least two threads which it was done at the same time. So I made the comment.


Yeah, I made a comments on those 2 threads as that's the one I want to check out when I got home... Like I said, didn't know about some options because I was using my phone and haven't got the hang of Tapatalk features. For that I apologize and if it bothers You that much... Sorry


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## Bigdaftboy (Jul 28, 2014)

drunken monkey said:


> No, I see them as suppositions because you are making assumptions based on your observations without any firm facts.
> As I said before, you may well be right in your assumptions but it is wrong that you make those assumptions to be known, confirmed facts.
> 
> I can say that the next Ferrari V8 will have more bhp than the current one in the 458 Italia.
> ...


You were right about Ferrari then lol


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## jawshoe (Oct 24, 2016)

i'm still having a hard time getting the answer i was looking for. So approximately what year or serial did the 2500D movement begin being used?


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## Iowa_Watchman (Jun 16, 2013)

jawshoe said:


> i'm still having a hard time getting the answer i was looking for. So approximately what year or serial did the 2500D movement begin being used?


Should be serial numbers 8525xxxx and higher.


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## mjoranga (Jul 19, 2015)

And that's probably late 2010 to 2011 just before they release the PO 8500 right. ? 

Sent from my SM-G900F using Tapatalk


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## injurylawyer (Nov 7, 2008)

Mystro said:


> On a side note. the Planet Ocean only has had the 2500C movement from its introduction. It has recently received the 2500D movement. Only time will tell what if any advantages or disadvantages the 2500D movement has over the 2500C.


I know the post is from some years ago...I know most of the Planet Ocean's had the 2500C movement but when did the 2500D movements start shipping with the watch? I am curious as I have a Planet Ocean that was purchased in April 2011 and was tyring to figure out whether mine would have the C or D version. Any insight would be appreciated.


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## sportsmaven20 (Sep 16, 2010)

injurylawyer said:


> I know the post is from some years ago...I know most of the Planet Ocean's had the 2500C movement but when did the 2500D movements start shipping with the watch? I am curious as I have a Planet Ocean that was purchased in April 2011 and was tyring to figure out whether mine would have the C or D version. Any insight would be appreciated.


From Iowa_Watchman above (post #130)...2500D movement should be serial numbers 8525xxxx and higher.

If your serial number is 8525xxxx or higher, then you have a 2500D movement...if your serial number is lower then 8525xxxx, then you have a 2500C movement.


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## cybercat (Aug 8, 2013)

injurylawyer said:


> I know the post is from some years ago...I know most of the Planet Ocean's had the 2500C movement but when did the 2500D movements start shipping with the watch? I am curious as I have a Planet Ocean that was purchased in April 2011 and was tyring to figure out whether mine would have the C or D version. Any insight would be appreciated.


Quick n easy way to spot = the datewheel fonts are different on the PO with 2500D from the 2500C.

Old post from 2017 (post #628 in WRUW thread) explains with pics :
The WRUW Mega thread!

Will.


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