I have a question about my awesome Speedmaster pro (311 model). The manual says not to over wind the watch, which makes sense. I noticed that when I wind it until it stops, if I were to add a bit more pressure turning the crown in the same direction as if I were winding further, the ticking sound of the watch running increases, almost as if it were running in double time. I'm guessing it's normal, but what is technically happening at this point? Is this one of the reasons why Omega says not to over wind? I should probably buy a vintage Speedmaster also, you know, just to be safe, right?

 

No.

You should probably buy 3, 4, or 10'vintage speedies to be safe!

 

Winding a manual watch.

You are winding the mainspring into a small tight coil and the only thing holding it from spinning in the barrel is the tail of the mainspring which is "bent backwards" so that it catches in the wall of the barrel.

As the spring uncoils, the windy bit in the barrel centre is held stationary by the click or ratchet, therefore the only way to release the force is for the outer end of the spring to push the barrel around in a circle. This is what powers your watch.

If the spring has been wound tight (the first "stop feel") your spring is now an almost solid coil and if you wind harder you are in effect, transmitting all of the extra force through the winding train, through the barrel and into the running train.

Do not do it.

This is my understanding of the issue, happy for further education.

Cheers

Jim

 

As Jim stated, winding past the point of being fully wound, you are putting more power into the system than the spring would on it's own. This added torque in the wheel train will cause the amplitude of the balance wheel to increase, so the wheel turns further than it should in each direction as the balance oscillates back and forth. Once it reaches a certain number of degrees (the specific point varies depending on the design of the watch) the impulse pin, or roller jewel, on the balance wheel will come around far enough to strike the outside of the pallet fork horn.

This striking causes a rebound effect, and the balance travels back in the other direction faster than it would if it was just being moved by the balance spring. This causes the balance to go too far in the other direction, again striking the fork horn, and this continues to happen until the power is reduced. This goes by several names, such as galloping (because it sounds a bit like a galloping horse), knocking, and rebanking.

This video shows what happens on a manual wind watch when you turn past the point of full wind - if you look at the top left of the frame you can see the crown and ratchet wheels turn as I crank on the stem to cause the knocking, and then let off and the rate returns to normal.

Knocking can be caused in a manual wind watch by doing what you are doing, but it can also have other causes, such as a mainspring that is too strong, incorrect lock on the pallet fork jewels, or in an automatic watch a fault in the barrel such as too much (or too strong) braking grease.

When the watch is knocking, it can run at a very fast rate - I've seen upwards of 900 seconds a day fast on the timing machine. This is one reason why Omega advises against this, but also it will put additional strain on the tang end of the mainspring, which is spot welded to the primary mainspring body. Although you would have to crank very hard to deliberately break the spring in one go, doing this repeatedly will cause fatigue and possible failure at this point.

I made the video above about 6 years ago now to illustrate this, but since then Lititz Watch School has produced a video showing it in slow motion under a microscope where you can actually see the amplitude build until the roller jewel hits the outside of the fork horn - if you go forward to about 1:40 in the video it will take you to just before that happens:

Hope this helps.

Cheers, Al

 

Doesn't get much clearer than that. Archer, you're an astonishing resource to have on the forum!

 

Wow, great explanation with videos! Thank you very much for explaining exactly why you should not over wind a watch.

 

Excellent explanation and vids! Al you are a great resource. I'm slowly learning new things daily.

 

Al, cheers right back to you, Sir! Thank you so much for the well detailed explanation and illustrating videos. I'll be sure to never hear that sound come from my Speedy again. I should probably still get a vintage piece though just to be absolutely safe.