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• #48642
brutusamiga
Participant

I need your help as I am at a lost here. I am working on a British GF clock. The clock runs ok but every so often the weights do a free fall of about 1/2. Bushings are fine and the clock has been properly serviced and oiled.

I thought that the problem is caused by faulty chains so I decided to measure the links fer foot and order new chains. It came to 43 1/2 LPF. I simply counted the links and thought it would be a reliable method but then I came across a formula to determine the correct LPF:

a: measure center to center of 2 teeth (in inches)
b: divide by 2
c: result of step b = x
d: 12 divided by x = LPF

Doing this gave me a result of 42 links per foot.

The only way I can explain the discrepancy is that the sprockets are worn. A few of them are visibly worn but still in a fair condition. The chain is still in a good condition.

Am I correct in concluding that a 43 1/2 LPF chain will have this effect on a sprocket that need a 42 LPF chain?

Let me add that all three chains are exactly the same.

Your expert opinions are appreciated. This is the first time I am dealing with such a problem and I need to be absolutely sure of the correct chain before I place an order (it needs to travel from the US to S.Africa).

Bernard

#53728
arutha
Participant

Hi Bernard,
looking at your pictures would suggest that the material used to make the chain is too thick, can you confirm if it is the same material thickness as your old chain or is the chain in your picture the original chain?
The sprocket teeth look ok. It is also worth checking your clicks, make sure the teeth are in good condition and the retaining spring is doing its job. Check the rims of the sprocket wheels as if these are bent then that could help to throw the chain. Try swapping the wheel that slips with another (if they are identical) and see if the same wheel still slips.
Let us know how it goes
Regards,
Paul

#53729
david pierce
Participant

Bernard,
From the top picture it looks like when the chain is wound, the sprocket tooth is up against the weight side of the link. As the clock runs, the weight and chain move downward until their combined weight overcomes the friction of the chain guide. At that point the chain links will slide to the other side of the sprocket tooth which is about 1/2 of a link.
david

#53730
brutusamiga
Participant

Well guys, a friend of mine offered to lend me his set of 42LPF chains from one of his grandfather clocks. The original 43 1/2 LPF chain slipped on several places but the 42LPF fits very well and does not slip at all. The clock is back on the test stand now. I think that sometime or another the chain was replaced with an incorrect set.

Thanks for the replies.

#53731
willofiam
Moderator

Hey Bernard, just for curiosity sake could you post a picture of the new chain your using, preferably on the chain wheel? thank you and great subject, keep om keepin on , William

#53732
brutusamiga
Participant

This 42LPF chain is working perfectly. After weeks of searching for the problem and listening to different (VERY different) opinions, I can finally rest. Nowhere in the US can I find a steel 42LPF chain so I will order it from Meadows & Passmore (UK).

#53733
willofiam
Moderator

Hey Bernard, congrats on figuring this out and thanks for the pictures. initially to me it looked like the chain was not sitting down into the chain wheel fully, would be insightful to see how thick the link is compared to your original chain links, where did you get the formula for links per foot? I would think 43 1/2 links per foot would be a smaller than 42 links per foot but it doesnt appear that way. I do not know enough about the chains to know if you can get different thickness links, if that makes any sense? This is a great subject but to me we still have unanswered questions, or is that just me? Have a great day, WIlliam

#53734
brutusamiga
Participant

I fully agree; this is interesting and understanding this topic might make our lives so much easier when we are confronted with this problem.

I still need to understand why a 43 1/2 LPF chain in GOOD shape does not work, but a 42LPF works perfectly.

The formula I got here: http://mb.nawcc.org/showthread.php?64198-wrong-chains-on-a-1930-s-Mauthe

Tomorrow I’m going on a 3 week holiday and when I return I will tackle the cuckoo with the music box I can’t sync.

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