English lever pocket watch very low amplitude

[clockboy]

This is an fusee English lever pocket watch. The customer said that it was only running for a few minutes and then stopping. On first inspection the amplitude was almost non existent but strangely was running. I presumed a good service would resolve this issue BUT alas the same issue. I stripped again and inspected every part with a microscope and found a bent guard pin + the banking pins had been bent. Apart from this I could not find anything. The balance pivots show some scoring but just a tiny touch it swings fine. Believe it or not, the amplitude now (see vid) is twice as much as what it was. My suspicion is the pallet is not the original and the horns are just a touch short so the impulse pin is not swinging the hairspring on impulse. Just wondering if anyone has come across this error,I'm a bit lost at present.

 

 

 

 

[rodabod]

With the pallets removed, does the train feel like it’s running freely? And how about as you increase the winding power?

If the power delivery looks respectable, then I’d check for something else obvious like mis-locking. How do you adjust the banking pins in terms of their orientation?

I knocked up this crude little brass tool recently for correcting some banking pins on a JLC. It’s easier with modern movements are you are more or less just uprighting them. 

[watchweasol]

Hi  Whats the balance like when fitted on its own, is the rotation the same or is it a better swing. Balance spring looks a little small ?.

[Joseph111]

I have had a similar problem with a (Swiss) lever escapement. It appears to be caused by the pallets of the lever being slightly too far from the escape wheel and under engaging. I think the escape wheel may be released slightly too early which causes it to push the lever back the other way due to it engaging the other pallet too early. I think this then means that the lever never allows the balance wheel to release.

My problem was ultimately due to a missing pin that aligned the escape wheel bridge which I still haven't fixed properly (as I haven't had time to make a new pin) but have managed to get it going without (it is my own watch) by carefully adjusting where the bridge is with a screwdriver.

Edited April 5, 2020 by Joseph111
Slight clarification

[clockboy]

Thanks Guys. The train of wheels run free with no issues. I did the locking test suggested in the  various  books I have and the lock is good and equal using the banking pins as a gauge. The banking pins had both been bent in one direction and I just put them back vertical and straight. The guard pin had been bent further away from the roller which I have also made vertical and straight. These adjustment that had previously been made I suspect had been done trying to resolve this issue.  Tomorrow I will polish the roller jewel and horns first, if no improvement then I will first bend the guard pin away again to see if it improves. I am sure this is where the fault is. It is the impulse pin not realising correctly or the guard pin rubbing.The biggest problem with these English watches is there is no easy visual access to see whats happening.

[clockboy]

UPDATE: It looks like I have found the fault. I followed meticulously Henry B. Fried's tests from his book.  "The Watch Escapement"   and the escape passed all of the tests . So I concluded the only other fault it could be is the balance/hairspring. I removed the roller table (not easy as this has at the H/S underneath as well) and Hairspring for close inspection. When I assembled the balance and gave it a puff of air it spun BUT stopped abruptly. This is not good, it should spin and slow gradually.  See vid and the picture, which is not the best quality and I took it using my mobile through my microscope. The end of the staff is wedged shapped and very badly scored. I have tried to repair the staff but now it is way too short so I will have to make another staff. What fun !!!

 

 

[watchweasol]

Hi  Thats some stop, Pivot looks well worn.  Good luck with the turning.

[clockboy]

3 hours ago, watchweasol said:

Hi  Thats some stop, Pivot looks well worn.  Good luck with the turning.

Thanks just a bit annoyed with myself not spotting this fault earlier. 

[Tmuir]

Atleast you now have found the problem and it can be fixed.