Author Topic: A question of ratios  (Read 6800 times)

Nick

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A question of ratios
« on: November 03, 2006, 09:08:06 PM »
Hello all,

I'm a blacksmith in Upper Michigan, and a lot of my work is small and intricate.  A bladesmith friend of mine likes to tease me about it, and tells people one of these days I'm going to make a watch.  So, I'd like to make a clock and give it to him as a gift.  That's a bit of my background, most of my experiance is in metals, and that's what this clock will be (I'm actually not very good with wood at all!)

Even though I'm not building a wooden clock, I have some questions about clockmaking that I hope someone can help me with.

I think I've got the basics of the clock worked out, it's based on a 16th century clock.  I've studied several clocks, both metal and wood, and I hope I've come to a solution that's both functional and basic.  As a first attempt, I don't want to overdo it to much.  I've learned some of the terms, but please forgive any gaffes I make.  If I'm not clear enough I'll try to explain better.

The clock is a verge and foliot escapement.  The crown wheel is connected to the drive wheel by a pinion, then the drive wheel is connected to the wheel with the hour hand with another pinion.  I've seen clocks made with this 5 gear system, but I've also seen them with another gear and pinion between the escapement wheel and the drive wheel.  I don't know which is more efficient, but I went with the simpler method to make it easier to construct, though for future projects, who knows?

This is how many teeth for the gears I've figured out, in order from crown wheel to hour hand wheel.  I admit that this is gained through observation of other clocks, not math.  That's one of the reasons I'm asking for help.
 
Crown wheel: 49
pinion: 10
Drive wheel: 100
pinion: 4
Hour wheel: 50

Is this completely off base?  I can post the sketches I've made if it'll help, or a picture of the clock that's closest to what I'm planning.

Thanks,
Nick

Offline Bruce Robertson

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  • Bruce Robertson
A question of ratios
« Reply #1 on: November 04, 2006, 07:03:54 AM »
Nick,
I have plans for a pocket sun dial, It could be constructed fairly quickly and your friend would get off your back! email me for plans, [email protected]

Dave

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A question of ratios
« Reply #2 on: November 04, 2006, 01:48:12 PM »
Hi Nick, heres a train from one of J Wildings books, how to make a simple 16th century style clock  isbn  0 903512 47 5 . Main wheel 72 teeth- 2nd and hour wheels 48 teeth- crown wheel 20 teeth. The main wheel carries a pinion of 4 pins which drives the hour wheel. The crown wheel has an even number of teeth and the escape arbor is off set to make the esc work but you can use 19 or 21 and adjust to suit. All wheel are 1 module, the escape wheel needs a fly cutter, hope this helps, Dave ps ever thought of joining the mlhorology group at yahoo

Nick

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A question of ratios
« Reply #3 on: November 04, 2006, 04:36:05 PM »
Dave,

Thanks for the info, a couple questions to clarify:
I found an early 20th century text on Project Gutenburg that states the crown wheel should always have odd number of teeth.  Was that incorrect, or does it not matter that much?

"Main wheel 72 teeth- 2nd and hour wheels 48 teeth- crown wheel 20 teeth. "
What is the 2nd wheel?

And last, what do you mean by fly cutter?  I haven't come across that term while I was studying clockwork.

I haven't seen the yahoo group, this is actually the first forum I found for clockmaking.

Thanks,
Nick

Dave

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A question of ratios
« Reply #4 on: November 05, 2006, 12:48:44 PM »
Hi Nick, from the numbers given, you could say that the main wheel is No 1, next wheel No 2 and then the escape wheel. The 2nd and escape wheels have pinions of 8 leaves. You could have an escape wheel with either 19 or 21 teeth. A fly cutter is made from carbon steel that is shaped to match the profile between the escape wheel teeth. In other words, it matches the waste metal that is removed from the wheel rim, hope this helps, regards Dave