Here are a couple of internet pictures, this is a flightmaster 911 with a Delrin brake and then a 861 from a MKII. I just had a quick look in MWO who suggest that it was introduced in 1971

 

That's hilarious - the plastic brake "improved the movement's longevity"

 

Such a shame about the caseback

 

I'm assuming delrin reduced cost in some way, more that it being better in any measurable sense.

 

I think the Delrin brake does improve longevity, by causing less wear to the the wheel.

 

My question to you would be how does the wheel wear exactly from the steel brake?

 

Friction?

 

From what?

 

Applying some force to the wheel, plastic brake on metal wheel seems more gentle and forgiving than metal brake on said delicate wheel.

Come on let’s end the suspense, what am I missing?

 

Fixed!

@johnnylarue : Be patient and wait for love. It’ll be worth it. Don’t settle for less.

Now back to another delrin brake debate...

 

Force isn't equal to friction. I'm just trying to encourage you to think it through...

For the wheel to "wear" there would need to be both force and movement while the brake is acting on the wheel.

 

I see, so the brake is not stopping the wheel, just holding it in place? I am not a watchmaker so I assume some friction in this process and don’t fully understand the mechanics involved.

Are you saying it is not a performance improvement and just a cost cutting exercise?

 

I know Delrin parts were liberally used in the Lemania 5100 (and presumably its Omega equivalent?) under the pretence that they were more effective at absorbing shocks, much to the chagrin of we collector types. I don’t service watches so I can’t comment on how many of those parts have failed over the years, but I do know that movement has a better-than-average durability rating...

Moreover, I wonder how much money could have been saved in manufacturing an 861 by subbing in a single specialized plastic part for a relatively simple metal one?

 

What I can say, is omega would not have kept using a steel brake in the display back models if they thought it was less reliable or notably inferior. In truth, they didn't want customers seeing plastic in their high priced timepiece.

 

It's okay - you are pretty much there even though you are not familiar with the technicalities. First, the name "brake" is completely misleading, and the proper name for this part is "blocking lever" and that more accurately describes it's function. When people think of a brake, they think of how a brake on a car works, and that is not at all how this works. I just shot a coup0le of videos in slow motion using my phone, and have edited them down and uploaded to my YouTube channel that will illustrate how ridiculous the claim made by Omega's marketing team is.

In the video below I show the process of stopping an already running chronograph on a Cal. 861 (that is in my own 1971 Speedmaster). You will see that when I press the stop pusher, the operating lever moves the cam, and two main things happen. One is that the coupling yoke moves away from the central chronograph wheel, and the teeth on the coupling yoke wheel and the chronograph wheel are no longer engaged - this stops the wheel chronograph wheel moving.

The second thing that happens is that the blocking lever (in this case the two piece steel version) swings in to hold the chronograph wheel in place, so it doesn't move and you can read where the hand is that is attached to the other end of this wheel. These two things happen very close to each other in terms of timing, but the teeth of the coupling yoke wheel are only very slightly engaged with the teeth of the chronograph wheel - in fact Omega calls for the teeth of the coupling yoke wheel to only mesh to 1/3rd the depth of the very fine teeth on the chronograph wheel, so almost as soon as that coupling yoke just starts to move, the chronograph wheel is no longer being driven. Here is the video - first from a distance and second zoomed in on the phone so the quality goes down a bit:

The next question should be: "Hey Al, how many chronograph wheels have you replaced on vintage Speedmasters with the steel brake, due to excessive wear on the teeth?" My answer is "zero" so the idea that the steel versions cause excessive wear on the teeth of the chronograph wheel, is just simply not the case. I won't say there's no wear on these, because if the watch gets a jolt when the chronograph is stopped, it may cause the hand to move and there would possibly be wear at that point, but in the big picture it's insignificant.

That "simple metal one" is actually two parts, not one. One of those two parts is an assembly in itself, with the pin added, so in total there are three parts. To machine those three parts, assemble two of them into one part, making sure they are in tolerance, deburred, etc. is not cheap. In contrast you make a die for an injection molding machine, and pump out the single piece plastic brakes by the tens of thousands before you need to replace the dies. It's a no brainer that the plastic version would involve significant savings when comparing the price of the two parts. If you look at the context of the whole watch it's not likely much, but that's not how production improvements work in an industrial setting - cost savings are largely done through smaller incremental changes like this. I think to put this in today's context is a mistake. Remember this change was made during the height of what would be the quartz crisis, and Omega was looking for any type of savings they could find I suspect.

I don't have the prices handy, but what Omega charges for the two steel parts compared to one plastic is quite different - I know I've put the numbers up before. Anyway, have to run so I'll let you all consider this for a few hours...I'm off to go taste and buy some wines...

Cheers, Al

 

There’s no debating that the Delrin brake is a visual blight on an otherwise very handsome movement, so that’s understandable.

As for the rest, only an experienced watchmaker (looking at you, Archer!) could provide the kind of anecdotal evidence we need to establish the relative viability and longevity of Delrin in a 50-year-old movement. Looking ahead, I would wager not even the folks who created Delrin can say definitively how its molecular structure will hold up in 100 years, but I imagine they’d confidently assert that it certainly won’t rust.

 

Other hypothesis, is that the brake will at least damage the triangular shape of the chronograph wheel and will make teeth less pointy.
And when activating the chrono it may increase the risk that a tooth of coupling yoke wheel will meet a "flat" tooth of the chronograph wheel and stop the movement.

But you may have to use intensively your chronograph to be exposed of such risk of hammering the triangular shape.

 

I'm in the process of signing up for a second OF forum account so I can Like this twice.

 

Ha! Thanks, for the encouragement @airansun. I'm about 95% settled on the on the long-term beauty potential of the Euro watch with the yellow lume. Now just working on shipping details and establishing whether the total pre-service cost is viable. Note that I've been after this watch on and off for a few years now so I'm having to weigh the patience strategy against my own life expectancy at this point.

Thankfully I've kept a folder of some of the nicer all-original MKII's that have come and gone over the years and this one seems to measure up in the bang-for-buck department.

 

“Hey Al, how many chronograph wheels have you replaced due to damage from the steel blocking lever damaging the teeth?”

Answer...zero.

For the price discussion, this is from this summer, the last time this debate happened in earnest....

“ the plastic one is one piece, and costs $88 Canadian at the moment, where the steel version requires two pieces and they are $105 and $88, so the steel version is more than double the price.”

I’m sure it will happen in another 6 months or so...

Cheers, Al