Movement evolution

I wasn't sure where to put this thread, but since this can apply to any watch brand of any vintage, I suppose this is the best place. I think there are some well known changes that have happened in various watch movements that people are aware of, for example the switch from steel to the plastic "brake" in the 861 movements, even though the steel is still used on watches with display backs.

Another is a symmetrical clutch bridge in the 321 changing to an asymmetrical design, and the shape of the regulator going from a sharp pointed style to the "lozenge" style (and along with that a change to the balance that many aren't aware of). But other more subtle, and often hidden from view, changes also happen on various movements, and I wanted to illustrate some to show people that movements are almost constantly going through small changes for different reasons.

So sticking with chronograph movements for a bit, here are some observations people might find interesting.

Sticking with the Cal. 321, this is the friction spring that is used for the chronograph wheel - this spring prevents the wheel and the central chronograph seconds hand from having that stuttering motion you sometimes see when it isn't adjusted properly:



You can see that the spring is a forked shape at the spot where it would contact the underside of the chronograph wheel, and there is a relief machined into the wheel train and barrel bridge that is centered on the hole in the bridge where the center wheel can be seen. Here is an earlier version of the 321, and you can see this is a different design:



Here the friction spring doesn't have that forked end, and it's offset to only contact one side of the chronograph wheel. The relief machined into the bridge is also off center.

So the differences here aren't just what you can see in those photos, and here is a shot of the two screws that are used to hold these springs in place:



On the left is the screw that is used for the very first photo with the forked spring. You can see it has a small shoulder on it, and this means that when the screw is tight, the spring can float - in fact this is one of the first checks to be made on the chronograph mechanism as you are assembling it. The one on the right is for the older version, and the spring is held rigid when the screw is tight. Here are both screws and both springs:



What is sometimes difficult is to figure out why these changes were made. My guess here is that the forked spring does a better job at controlling the stutter of the wheel, and therefore the hand, and this design continues through the 861, 1861, and even the new 3861.

Here's a shot of the dial side of the same movement shown above in the first photo:



The lowest arrow points to the hour recorder stop lever - this is what prevents the hour recording wheel from turning when the chronograph is turned off. The upper left arrow points the the stop lever spring, and the right arrow points to the hour recorder hammer. Note the shapes of all three of these parts. Now let's look at the earlier movement:



So you can see that the stop lever has a different shape in some areas. The area where the spring engages with the lever is deeper, and the part of the spring that meets the lever is larger and more squared. The end that interacts with the hammer is also quite differently shaped, and you can see that the pin on the hammer that contacts the lever (to move it out of the way when you reset) is much larger.

Closer view of the spring:



Closer view of the hammer:



In the above photo you can see the shape of the stop lever where it contacts the larger pin of the hammer. Here is a view of both designs in profile - new stop lever on the left, and the early design on the right:



And here a view of the area where the pins contacts these same parts - new one on the right here:



So why were these changes made? Good question, because the older design looks far more robust than the new design does, so this one I don't have a good answer for.

Turning now to something other than a chronograph, here a center wheel for a Cal. 550 series automatic. Note that in the end of the center wheel there is a brass bushing installed:



This bushing is what the center seconds pinion goes through, and it helps keep that pinion from wobbling all over the place. It is a press fitted part, and I've had numerous watches come in with this bushing either half falling out, or completely missing. Omega has redesigned this part to eliminate the separate bushing entirely, and now is is integrated right into the shaft of the wheel:



This change is considered a mandatory upgrade by Omega, so when a watch comes in with the old style, they want it upgraded to the new style to prevent failures down the road.

I'll post more examples when I have time, but what I wanted to illustrate is that movement designs are not static, and things are always being tweaked for various reasons. Some could be for quality issues, others for cost savings, but the designs many think of as being constant, really are not in many ways.

Cheers, Al

Here are a couple of changes found on the 861 series. The spring for the coupling yoke on early models is different than the one for later models, as seen from the underside:



The top one is found on the earlier models, and the bottom one is found on later models and through the 1861 series. The difference is that small step that is machined into the later version. Here they are in situ, first the older style:



The spring simply butts up against the coupling yoke in this design, and now the later version:



Here you can see that the spring overlaps the coupling yoke. Again not 100% sure of why this change was made, but my suspicion is that this change was made to keep the spring from disengaging from the coupling yoke if there was a shock. Note that both of these watches were old enough to have the steel brake, so the change to this part appears to pre-date the change to the brake material.

Another change that happened in the 861 series is to the hour recording wheel. Here is what the wheel used to look like:



This wheel is under the dial and the post that is on the wheel is what the hour recording hand is attached to. You can see there is a "heart shaped" cam that is attached to the wheel, and this is what the hammer contacts to reset the hour recording hand. The cam used to be attached to the wheel via a small screw, so if needed the cam could be changed (or the wheel) if either of them wore out. The problem with the design is this:


This is how the watch in question came in - the screw had fallen out of the cam, and the hour recording hand would not reset as a result. This one was easily put back together, so it was still fine, but this was not an isolated thing (it was the second one I'd had that came apart inside a month) and this was obviously something that Omega wanted to solve, so this is what a new wheel looks like:



The cam is now riveted to the wheel, so this is all one assembly. If any parts of it is bad, the whole thing is replaced. This change was made some time ago because I've never seen the came and wheels for sale separately, so these are actually not all that common in the 861's, and I tend to see more of them in 321's (this is the exact same part in both watches).

Cheers, Al

+1. Fascinating stuff, Archer. A somewhat related question: Do we know for certain at this point whether Omega will phase out caliber 1861 In favor of new caliber 3861? If there is no definitive answer at this point, what is your opinion? Thanks!

I don't think anyone knows "for certain" if that's what will happen. I find it unlikely that they would develop the 3861 and only use is in a couple of LE's though...

Omega publishes three levels of technical documentation that I have to keep track of, and updates are made on a regular basis.

The first are the technical guides for each movement, which include exploded views, order of assembly, indications where to oil and what oil to use, as well as a list of parts.

The second level is called "General information for Calibers" and these are for each movement "family." So this will cover a range of movements that are all related or based off one another. For example the document for the 550 family covers the 550, 551, 552, 560, 561, 562, 563, 564, 565, 750, 751, and 752 movements.

The third level is called Work Instructions, that are less product specific. These tell you things like general rules and procedures for lubrication, hand fitting procedures, quality control checks, pressure testing, and all kinds of tasks that happen in the shop that apply to a variety of watches.

It's in the second level documentation that if significant design changes are made, that you will see the reasoning documented. These documents also may include other information than just part upgrades, so for example if I look at the new Cal. 3861 movement for the anniversary Speedmasters, the technical guide shows all the thing I mentioned above. But in the General information document there are already a couple of part upgrades, they list what the end shakes of all the wheels are, all the chronograph checks, etc. So there is a lot in these documents.

Omega didn't always publish such documents, and even the modern technical guides that tell you where to oil are are really a fairly new thing - in the past watchmakers were expected to know this stuff through their training, but as movements became more complex, these guides started to include more information.

So for parts that are upgraded, in many cases the part number will change, but not always. If it does change the document will give you the old and new part numbers, or will tell you physically how to tell the old part from the newly designed part. Of all the things I've shown in this thread so far, the only one that is shown in one of these general information documents is the change in the center wheel bushing from having that pressed in bushing to having the style that is integral to the wheel. All the others would have happened presumably before these documents existed.

So even though the 550 series movement hasn't been made for several decades, this is a fairly recent change, and many discontinued movements continue to have upgrades made to them.

Every time a document of any sort is updated, it is published in the news section of the Omega Extranet - this is not a public web site, but is an internal Omega site where technical information is. So every day when I log on, the front page that comes up will show me any updates, and when I see one, I download the documentation, and review the changes. Yes it an be a bit to keep track of, but for common movements I service I know all the upgrades that are needed, so I don't have to check the lists every time. For movements that I might not get that often, I do check it when I have the movement disassembled, the parts are all cleaned, I've checked them all for wear, and I'm gathering the spare parts for the service.

Generally I replace parts if they are worn, or if a mandatory upgrade is specified. Typically once an upgrade to a part is made, the only version that is available is the new one, so if a part like the center wheel is worn (which is common) then I'm replacing it for that rather than for the upgrade. Typically if I am replacing a part on a movement, I itemize each part on the invoice, and specify the reason for the replacement. I didn't always do this but it lets the owner know why I'm changing what I'm changing. This is all documented in the service documentation I provide with the service as well (photos and description step by step through the service), but not everyone reads those so I started putting the reasons on the invoice. If I replace a part for rust I'll say that, or wear, and if it's a mandatory upgrade, that's exactly what the line item on the invoice will say for that part.

Yes, other brands do these sorts of upgrades as well, but again these are published internally and to those with access usually via a parts account.

This is all part of the work done during a service that people aren't really aware of, as it happens "behind the scenes" so to speak.

Cheers, Al

Are the recording marks engraved in the hour recorder bridge also a feature that can be divided into the early/later 321 categories? They seem to appear on watches from all periods, yet some movements don't seem to have them.

That feature doesn't seem to have a set pattern to it that I have seen.