Clock Question #5

Hi,

I want to make the W.R. Smith Skeleton Wall Clock. It calls for a 108 tooth great wheel but with the change gears and hole plate I have with my dividing head I can't make 108 divisions. I got to thinking about it and it seems like the great wheel only transmits the power to the time train so can I just make the great wheel with any tooth count {105, 97,96,113,etc.] that I'm able to do with my dividing gear? I n other word the great wheel tooth count doesn't affect the accuracy of the time keeping?

Thanks,

Mark

144 people have read your question so you deserve an answer, Mark.

I don't know that much about clocks, but I do know that the ratio of hours to minutes to seconds gearing is critical (although I have a clock where the 'seconds' hand goes round in 45 seconds). The ratio of these gears to the escapement is also critical, but the initial drive wheel (great wheel) as you suggest only connects the string or the spring to the rest of the works. A smaller great wheel will (may) need a slightly heavier weight, and will run down a bit quicker, so as long as you mount the clock fairly high up, it should work ok. Or change the size of the winding drum to compensate (if weight driven).

Thinking more about it, any clock with a fusee has a variable drive ratio (as though its great wheel changed in size as the spring ran down).

Why doesn't a web site for Model Engineers recognise the word fusee, I wonder?

Cheers, Tim

Mark Seeing that its a skeleton clock just make sure that you can plant a smaller wheel otherwise smaller or larger is ok Incidentally I cut two 144 teeth wheels for a regulator in two goes of 72

Roy

If you have a dividing head 108 should be easy enough to do? If it is a 40:1 head then every 10 holes on a 27 hole plate will do it. If 60:1 then every 10 holes on an 18 hole plate. If 90:1 then 15 holes on an 18 hole.plate.

Hi,

Thanks everyone for the replies. My dividing head uses change gears from the mini-lathe and a homemade hole plate with 22,25, and it was supposed to be, 36 holes.The reason I can't do 108 teeth is because the 36 hole circle on my homemade hole plate somehow got made by me with only 35 holes.. If I had a 54 tooth gear I could do 108 divisions with the 22 hole circle. But that wrong hole circle has always bothered me so I've finally decided to make a new plate with at least the one row of 36 holes.

Mark

Standard dictionary - you need to add it to your local one.

Neil