Pocket watch 25mm looses time

[PaulRepairShop]

3 minutes ago, oldhippy said:

Where did you get a new complete cylinder balance from? They haven't been made in decades. 

It was a complete balance from a 10 1/16 ligne pocket watch, sourced from a large inventory of identified (ligne) parts I took over from a retired watchmaker. These vintage parts are indeed quit old, specially the parts for cylinder movements, and often usefull for repairs. The appearence of the balance is the same as the original one, looking at the no of spokes (3), wheel diameter, rim thickness  and rim cuttrough (round on the upper side and flat on the lower side) and blue hairspring (no of coils same as the damaged original one).

My previous experience with cylinder escapment pocket watches is that they can be more precise in timekeeping than this one: rather #sec/d instead of #min/d. And this one is about -2min/d or even worse when the mainspring gets more unwound.

[oldhippy]

There's your problem something like that is not interchangeable. To the naked eye it might look identical but it is not. Cylinders are not compensated so time keeping is not as good if it is out by about 5 minutes a day that is accepted, the really old P/W's which only had one hand would be out by about 20 minutes or more a day.   

[nevenbekriev]

OK, what is important when replacing cylinder is the diameter of cylinder, overall length and the height of the mouth. Diameter of course can be judged by the hole of the old balance - the new one must fit there tight. But, if You replace the balance completely, then You need to check 2 more things of greatest importance: one is that the outside cylinder diameter is small enough to get free between wheel teeth, and the other is that cylinder inside diameter is big enough that the tooth can get in with small free play. Of course, if You movement works flawless, then all this for sure is fulfilled.

2 min/day is not much. For replacing the entire balance from different unknown caliber, this is rather perfect match. Of course, the movement needs to be adjusted as the regulator to be able to make movement slower as well as faster than  0 sec/day. In You case, You can check if it is possible to decrease the depth (the distance between cylinder and the wheel) and still have enough drop lock. This will make the movement faster enough. If the depth can not be reduced without loosing the drop lock, then You always can shorten the hairspring to make the movement faster.

If You have moebius 8200, then wash the wheel and the balance and apply just a little grease on the cylinder surfaces where the teeth touch. Then compare the amplitude.

Edited November 17, 2024 by nevenbekriev

[PaulRepairShop]

2 hours ago, nevenbekriev said:

OK, what is important when replacing cylinder is the diameter of cylinder, overall length and the height of the mouth. Diameter of course can be judged by the hole of the old balance - the new one must fit there tight. But, if You replace the balance completely, then You need to check 2 more things of greatest importance: one is that the outside cylinder diameter is small enough to get free between wheel teeth, and the other is that cylinder inside diameter is big enough that the tooth can get in with small free play. Of course, if You movement works flawless, then all this for sure is fulfilled.

2 min/day is not much. For replacing the entire balance from different unknown caliber, this is rather perfect match. Of course, the movement needs to be adjusted as the regulator to be able to make movement slower as well as faster than  0 sec/day. In You case, You can check if it is possible to decrease the depth (the distance between cylinder and the wheel) and still have enough drop lock. This will make the movement faster enough. If the depth can not be reduced without loosing the drop lock, then You always can shorten the hairspring to make the movement faster.

If You have moebius 8200, then wash the wheel and the balance and apply just a little grease on the cylinder surfaces where the teeth touch. Then compare the amplitude.

Thanks for your indepth response! At the rebuild I checked the interaction between the cylinder and the teeth: the outside diameter is correct and sits well between two teeth were the teeth have enough moving space, also the inner diameter is correct were a tooth can run freely before it leaves the cylinder via the exit impuls. The height is also good were the teeth do not touch the upper and lower edge of the open gap cylinder.

The distance between the cylinder and the wheel is as close as possible and cannot be decreased.

I intend to the decrease lenght of the hairspring and check any (expected) improvement in time loss.  I used Moubius 941 for the same; is 8200 a better choice for the cylinder escapement?

[nevenbekriev]

33 minutes ago, PaulRepairShop said:

The distance between the cylinder and the wheel is as close as possible and cannot be decreased.

I intend to the decrease lenght of the hairspring and check any (expected) improvement in time loss.  I used Moubius 941 for the same; is 8200 a better choice for the cylinder escapement?

What I meant is that You need to increase the distance between the wheel and cylinder as much as possible (to decrease the depth) This leads to increase of the rate.

Sorry if I say things that You already know, but I actually don't know what You know. In cylinder movements like the one You show, there is upper and lower balance cocks that go together and they together can be moved in order to regulate the depth. Once the depth is regulated in the factory, holes are drilled and pins placed to fix the downside cock to the plate. But, when cylinder is replaced, this regulation not always is good anymore and then the pins can be slightly bent or removed or holes enlarged to allow slight movement of the cocks in order to find correct adjustment.

Yes, I believe that 8200 is better and there will be increase of amplitude.

[oldhippy]

If the cylinder is correct and has no wear then it is the weight of the balance and the length and strength of the hairspring. Be careful because of age these hairsprings can be brittle.    

[PaulRepairShop]

8 hours ago, oldhippy said:

If the cylinder is correct and has no wear then it is the weight of the balance and the length and strength of the hairspring. Be careful because of age these hairsprings can be brittle.    

I will first decrease the length of the hairspring (e.g. 1 mm) and check the effect on the rate. Also have to aligh the balance wheel dot/nick indication with the middle dot ( 1 of 3) stamped on the mainplate. Let you know the result.

I also noticed that the watch runs on time in case the mainspring is fully wound, during unwinding the rate then gets worse (upto 2 min/day). At full wind the amplitude is about 90 degrees.

[PaulRepairShop]

On 11/18/2024 at 7:29 PM, PaulRepairShop said:

I will first decrease the length of the hairspring (e.g. 1 mm) and check the effect on the rate. Also have to aligh the balance wheel dot/nick indication with the middle dot ( 1 of 3) stamped on the mainplate. Let you know the result.

I also noticed that the watch runs on time in case the mainspring is fully wound, during unwinding the rate then gets worse (upto 2 min/day). At full wind the amplitude is about 90 degrees.

Decreased teh length of the hairspring by 1 mm and regulated the collet to align the balance wheel nick to the middle nick (1 of 3 nicks) on the mainplate. The pocket watch runs very well now within a rate of 20 s/d (hanging position, so crown up).