Hi all,
I've had a bit of a look around trying to find an easy explanation of how the co-axial movements differ/improve on traditional lever movements. Does anybody have something simple? perhaps with comparative pictures side by side?

Edit: title should say "lever"

 

Title fixed.

Archer is the man to answer.

 

Probably the easiest way of showing how they differ is through the models they had at the training given by Omega that I attended. I shot these iPhone vids of each type.

Here is the Swiss lever escapement:

And here is the Omega co-axial escapement (2-level design shown):

In terms of the "benefits", with the Swiss lever escapement during the impulse phase there is sliding friction between the pallet fork jewels and the escape wheel teeth. This surface requires lubrication to reduce the friction between these surfaces. Typically Moebius 9415 is used for this, and it's a sort of a thixotropic grease, where it is more of a grease like substance under normal conditions, but liquefies under pressure, so it does a very good job of staying in place on the escape wheel and pallet fork jewels. In the past straight oil was used here, and it was easily flung off the surfaces that needed it.

With the co-axial, the impulse is done with more of a direct push with the jewels, and not two angled surfaces sliding on each other. In theory this requires no lubrication, but practically there are 30 points on the Omega 2-level co-axial escapement that must be lubricated. The 3 level escapement drops this down to 10 points. Here the oil on the co-axial wheel is used more for cushioning than it is for reducing friction.

The only benefit that Omega claims is increased service intervals. However, as I have said many times on various forums, the escapement is only one area of the watch that requires servicing.

Now if you want a truly lubrication free escapement, at a bargain basement price there are the Sinn Diapal watches, that use a Swiss lever escapement. However the escape wheel is treated with an anti-friction coating, and requires no lubrication at all on the escape wheel teeth of pallet fork jewels.

Hope this helps.

Cheers, Al

 

Another enlightening information from Al. Thanks !!!!

 

I figured, but I didn't want to put out the Archer sign just yet! (can we get a mock-up like we do for desmond!)

 

So, let me see if I understand. In the swiss lever:
The parts here are the balance (up top), the lever (middle) and escapement wheel (bottom).

Where I have 'circled' there will be friction when the balance wheel is released. It is this friction that is removed in the co-axial?

In the co-axial, the balance wheel is the top rectangular thingo, and the escapement is the middle wheel, which has a bottom wheel and a star thingo on top of it???? (Sorry all of the technical terms!

The bottom wheel is, for this simple model, effectively redundant? (i.e. it doesn't have a direct equivalent in the first model), so the 'co-axial' bit is the fact that the escapement has a wheel thingo AND a star thingo?



Also, wouldn't there be a small amount of sliding friction in the circled bit here (or is this the push friction you were talking about):


Thanks again!!!!

 

Explaining how escapements work is not easy without being able to talk face to face, but I'll try....

Let's start with the lever escapement. Yes the top part is the underside of the balance wheel with the impulse pin (roller jewel), then the pallet fork (or lever) and then the escape wheel. Here is a shot of the pallet fork inside a watch (Omega Cal. 861 I believe) and it shows the working surface of the pallet jewel - there is a small drop if oil placed on that jewel.



The picture you posted above of the lever escapement shows the escapement in a locked position, and although there is a bit of sliding friction when the escape wheel tooth unlocks from the side of the pallet stone, the major friction I was referring to is during the impulse. This is when the impulse pin (roller jewel on the bottom of the balance wheel) is inside the fork horns of the pallet, and the escape wheel tooth is pushing on the pallet fork. This is what gives the impulse to swing the balance wheel around.

In this photo, you can see the tooth part way across the face of the pallet stone, and this is what it would look like when the tooth is giving the impulse to the pallet fork, Here the wheel is rotating CCW, so the tooth is moving from right to left, pushing on the jewel and causing the lever to flip, and push on the impulse pin on the balance:



Lubrication here is important, and too much or too little can cause problems.

In the photo of the co-axial escapement, the terminology is a little different...

At the top we still have the underside of the balance wheel, but in addition to the impulse pin (roller jewel) there is another jewel in the roller that looks like a pallet stone. Next we have the pallet fork, and it is a different shape that the lever style obviously, and it has 3 jewels instead of 2. Next is the co-axial wheel, with the star thingy on top, to use your terminology. And he last one is the intermediate escape wheel.

There is sliding friction in this escapement between the teeth of the intermediate escape wheel, and the upper co-axial wheel teeth (those are the star shaped thingies). This is actually the trouble spot in the 2-level design, and this can cause issues with the function of the escapement, and what is known on WUS as "the stopping problem."

Now the shape of the jewels in the pallet fork and the extra one on the roller are similar to what is in the lever escapement, but the working surfaces of those jewels are all quite different. The angled surface that is the sliding surface on the lever, is merely clearance on these jewels, and it's mostly the sides of the jewel that are in contact with the various parts.

There is a tiny bit of sliding happening at the point you circled, but I can't stress enough how small it is in relation to the lever escapement.

The lower teeth on that co-axial wheel are very small, and very sharp. Just how small? Well here is a little demo for you to show you how small...

Here is a Cal. 2500 mounted in a movement holder that is specifically designed for checking and oiling the co-axial escapement:



Here I have used a regular old straight pin to show the size of the hole that I oil through on the dial side of the movement:



Now moving to the microscope, here is that same pin beside the co-axial wheel:



And finally, here is the wheel under 50X power, showing how I have oiled one of the teeth on the co-axial wheel:



Hopefully you can see the drop of oil I have placed there. I can assure you it is very small, and this is the oil that helps protect the wheel from impact damage. If the wheel is not properly lubricated, you end up with this sort of damage to the teeth:



So the contact between the jewel and this tooth is almost a "point contact" rather than two large areas that are sliding against each other as you have in the lever system.

Anyway, I hope this helps.

Cheers, Al

 

I think I understand......
THanks again for devoting so much time and effort to us "ooo shiny" collectors!

 

Now that you've absorbed Swiss Lever and Co-axial knowledge, it's time for you to look at the AP version

 

Now that you've absorbed Swiss Lever and Co-axial knowledge, it's time for you to look at the AP version

 

This is an updated Robin escapement...invented in the late 1700's...

Cheers, Al

 

ahh. my brain is hurting. but i like the video

 

Buy this book and your head will explode:

 

That is the standard textbook for people in watchmaking school - it didn't make my head explode...

If you don't like the math inside, you can just look at the pictures.

Cheers, Al

 

I hope you are right Al, I've just ordered a copy.

 

It's been suggested to me before, but I'm certainly no writer...besides I'm too busy fixing watches. Had another Speedmaster come in this week - I think that brings the total to 14 in the shop. That's not counting other Omegas and other brands...