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double fusee bracket clock

rajeshvyas

By rajeshvyas
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rajeshvyas Member

rajeshvyas

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oldhippy, thanks. yesterday i tried with 20" same brass (0.8mm thick) hand but it did not worked it stopped between 7-9 position. then i reduced the length to 18" + reduced the thickness to 0.6mm and it worked-and still it is working keeping perfect time. can u suggest me the best suitable (especially for such large size clock) some more light metal for making hands? i am also planning to make rib to give more strength.   

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Tudor Distinguished Member

Tudor

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Aluminum would be my choice if it needed to be longer. You can go quite thin and place a center crease in the hand to stiffen it along it's length (or curve it)

You can always "skeletonize" whatever hand you choose too, and I think the counterweight idea was already mentioned, for the opposite side of the pinion.

Poising the hand on it's pinion should eliminate the "positional error" of the load on the movement, so it's not faster after noon as compared to before noon. Something crude would do- it wouldn't need to be "balance wheel" perfect.

I have often pondered this with wristwatches (poising the hands), but there isn't much point, due to the infinite positions the watch is kept in at any time. But a clock on the wall is always "noon up" so it's a bit easier to manage I think.

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oldhippy Distinguished Member

oldhippy

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The movement is all ready fitted with the counter weight. Aluminum will be to flimsy and skeletonized hand will not be in keeping with this movement. I'm pretty sure the movement is the type that would be over hanging a shop or in a large hall type room. 

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rodabod Distinguished Member

rodabod

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I think I’ve only just understood this “counterweight” query. So, there is already a counterweight attached to the motion works..... if you disengage the going train then you’ll be able to judge what length of hand counteracts the built-in weight. 

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rajeshvyas Member

rajeshvyas

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rodabod, yes the counter weight is already fitted to the movement. now to judge the length of minute hand if i disengaged the counterweight then how i will know the load carrying capacity of the movement? i have already tried with 18" brass 0.6mm thick hand which runs perfectly OK. today i am increasing the length to 20" and again try. if 20" works well i guess i must stop more experiment and finalize the length! 

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rodabod Distinguished Member

rodabod

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One thing to watch out for is the excessive positive drive that you could get if the hand was significantly heavy and falling (so, say at the 15 minute mark).
 

Recoil escapements are good at dealing with varying drive/amplitude, but it doesn’t necessarily make it a good idea to design it to vary significantly. 
 

 

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