Restarting a stopped balance wheel after winding + amplitude question

[meillier 0]

Hi.

 

Sorry if this is answered in another post. I have spent a LOT of time searching for that answer here and online and really couldn't find anything besides one post for another forum which I will include down below.

 

Essentially, my 6 months old TAG Grand Carrera Calibre 36 started to not hold its charge so much for about 1 week or so before I found the watch completely stopped and unable to get it to after winding it a bit.

 

My question was, given that the balance is at this point no longer oscillating. Even if I give the watch a good wind, what will get the balance wheel to start again.

I mean at this point, the pallet jewel is in contact with the tooth of the escapement wheel. Adding more tension to the main spring by winding the watch only make the escapement wheel push harder against the pallet wheel.The escapement wheel is thus solidly locked in position waiting for the pallet fork to be moved and disengage the escapement wheel.

 

So my two questions are:

 

1/ Restarting the balance wheel

Do you have to give the balance wheel a little manual push to get the watch to run again? how does the watch get started again? Shake it to dislodge the pallet jewel from the tooth of the escapement wheel?

I have read that it should start by itself automatically but understand how though.

 

2/ having the balance wheel oscillate with the right amplitude.

say you were to manage to dislodge the pallet jewel, the following post is the only answer I found that explains why a balance wheel keeps oscillating as opposed to slowly losing momentum over time:

 

 

Energy is transferred from the escapement (and thus ultimately from the mainspring) to the balance spring every time the pallet moves from one side to the other.

 

Suppose we start when the balance is freely rotating, with the impulse jewel not touching anything. The pallet is resting against one of its banking pins, held there because the geometry of the pallet jewel that is currently in contact with the escapement tooth was designed to do just that - hold it against the pin. As the balance rotates back towards its neutral position, the impulse jewel moves into the slot in the pallet fork, and the balance starts pushing the fork away from its banking. At this point, the balance is actually transferring energy *to* the pallet fork and escapement wheel.

 

But as soon as the pallet fork moves a few thousandths of an inch, the pallet jewel moves away from the escapement tooth enough to unlock the escapement, and the escapement wheel starts rotating forward. The escapement tooth slides along the angled face of that same pallet jewel, and the angles and arcs are now designed to transfer energy in the other direction, to the balance. The mainspring applies torque to the escapement wheel, the escapement wheel tooth slides along the pallet jewel end, and this pushes the pallet fork in the direction it's already going. The pallet fork "catches up with" the impulse jewel and the other side of the fork starts pushing on the impulse jewel, speeding up the balance a small amount. This continues until the impulse jewel leaves the slot in the pallet fork, the pallet fork is stopped by its banking pin, and the other pallet jewel locks the escapement wheel from moving any further (not necessarily in that order).

 

So each time the balance interacts with the pallet, it first uses a little energy to unlock the escapement, but then gets "kicked" by the escapement through the pallet, for a net gain in energy.

 

The above was written with a standard lever escapement in mind.

 

Assuming this is correct, will the balance wheel slowly build up momentum at each new push until it reaches the amplitude it is designed to have for the timing to be correct?

I read somewhere else that on an 7750, the balance wheel need to oscillate with an amplitude of roughly 270 degrees (I forget the exact range).

 

PS: Although I love the watch I bought and it is of good quality (~350$ model from a TD), my gut feeling it was very poorly lubricated causing the balance wheel to come to a stop after whatever low grade oil they used built up some gunk in the jewels. (hence why it is recommend to have the watch serviced when you first get it).

I say that because although manually winding the watch was very smooth when I first got the watch, it is now very rough. The same thing happened on another watch. I took it apart and checked the barrel bridge which has 2 wheels. The teeth are fine but turning it manually is also very rough on that one. Probably need good cleaning and proper lubrication....

 

thank you.

[cwazy1 0]

if i were in your situation the first thing i would do is to firmly give the watch a 'turn' much like turning a doorknob.

 

if that doesnt work, take your balance assembly out and reset it.

 

you should be good after that!

[Dendo 93]

My guess is that you can give the balance wheel a little push but it will run for a few seconds and sieze up again. It sounds to me as if you need to get it serviced and properly lubricated.

 

The correct amplitude is determined by several factors but not related to the energy going in. Obviously if no energy is going in there will be no amplitude at all but the balance wheel is like a pendulum and is designed to move at the same frequency regardless of the energy (wound spring potential energy) that exists. Having said that the amplitude does differ somewhat with how much the watch is wound, the position of the watch etc.

[meillier 0]

Thank you for your feedback. Appreciate it.

 

Cheers,