English Longcase Strike Problem

[svenedin]

If this problem has been covered before my apologies for repeating. I also apologise for not posting a pic but the clock is possibly fixed now and is back in the case.

The issue I have here is a strike problem with an English longcase clock with standard rack striking. Having overhauled this clock I noticed that it would tend to "limp" coming up to warn (as soon as the pin on minute wheel starts to engage with the lifting arm). The clock would still run but would lose power and almost stop until the rack was released at which point power returned.

I examined the movement on the bench. Everything worked fine with no power and released easily. With power on the strike train (provided with a finger) and the gathering pallet stopped on the rack stop pin, it became apparent that it was difficult to lift the rack hook and too much force was needed on the lifting arm to do this. This is what was causing the clock to limp when coming up to warn. Somehow the force of the gathering pallet on the stop pin caused the teeth of the rack and the rack hook to engage in such a way that it was hard to raise the rack hook. I decided to bend the stop pin upwards a little so that the gathering pallet stopped a little sooner. This seems to have eased the problem for now.

I just wondered whether this is a problem others have encountered and whether I am making a silly mistake. This is no evidence that the rack or rack hook have ever been modified so I just don't know why they tend to "lock" in this way. The cam shape of the gathering pallet suggests that if adjusted correctly it should slightly move the last tooth of the rack and the tooth of the rack hook away from each other so the rack hook should release with minimal force. I am puzzled as to how to adjust this correctly.

 

[R&A]

I would think that if the rack being lifted causes a power loss then decrease the spring tension on the rack. Not knowing which movement this is. I just did one similar to yours and had a power loss as the hammer lifted. I thought it was the spring tension on the hammer. I looked closer at the winding arbor and it was oblong. Who ever tried to polish the arbor before me. Well polished the arbor out of round causing a power loss. Plus I would check to make sure that the hammer is not lifting in warning , causing the movement to work to hard in warning. This would cause a loss in power. This might give you some different choices to check. Good luck.

H/C

 

[svenedin]

Thanks for the tips but the hammer is not being lifted in warning and I have tried it with the hammer off completely. It is also not the rack tail spring. Again I have tried it without. This is an English long case movement from circa 1800. The issue seems to be that with the gathering pallet stopped on the stop pin after the last strike there is too tight a lock between the rack hook and the last tooth on the rack. I can't work out why it is so tight to unlock. It must be some abnormal alignment

 

[R&A]

The one I was referring to was 1780. Check the tail, maybe bent. And needs to be adjusted. Or the arbor that hold the gathering pallet is bent. Take a micrometer and check the roundness of all the pivots on the strike train?

H/C

 

[svenedin]

Ok but they didn't have micrometers then! It is running and striking ok so far. The movement is contemporary to yours. I said 1800 but actually more likely 1790. Trouble is all the work over the 212 years. These movements should run like farm machinery in my opinion. They are primitive in a way by factory standards but yet extremely fussy where it counts. Truly hand made and very annoying! Still I love this movement.

 

[tom427cid]

Hi,
I have encountered this problem before,I found that the rack hook had worn just a bit and was acting like a locking taper. A couple of passes with a file to change the angle on one of the pieces and a small bit of grease has seemed to eliminate the problem.
Hope this helps.
tom

 

[svenedin]

Thanks Tom. You maybe on to something there. I had a look at the rack teeth and the rack hook under magnification. I couldn't see any wear on the rack hook but they was a bit on the rack. I thought it was probably not the cause but maybe it is. Somehow the angle of the gathering pallet on the stop pin creates a tight lock. My bend of the stop pin appears to have remedied the problem and the clock is not struggling badly to warn but it still isn't the easy release that I think it should be.

 

[svenedin]

Well this clock has been going well for a few days and I will see how it runs for the full 8 days. I have to admit that it probably requires more specialist attention than I can give it to bring it up to excellent working order. This was more a proof of concept of a clock that had been a non-runner for decades. The holes and pivots appear pretty good but there is a lot of wear on some of the pinions and that kind of work is beyond me. When finances allow it will have a professional overhaul and at least I have caused it no harm. In fact, my efforts have revealed a nice clock which is worthy of some money spent on it.