Author Topic: Common Clock Gear Trains  (Read 16807 times)

JoeComunale

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Common Clock Gear Trains
« on: September 09, 2005, 02:56:14 PM »
Center     3rd         3rd         Escape     Escape     Ticks         Pendulum     Wheel      Pinion     Wheel     Pinion       Wheel       Per Min.   Length
===============================================
112         14           105        14            60            60           39.14"
96           12           90          12           30             60           39.14"
80           10           75          10           30             60           39.14"
64           8             60          8             30             60          39.14"
75           8             60          8             32             75          25.53"
80           8             72          8             30             90          17.39"
108         12           100         10           32             96          15.28"

Excerpt from "Making Clocks" by Stan Bray (workshop practice series  #33)

Damon Miller

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Wheel counts
« Reply #1 on: September 10, 2005, 07:41:42 PM »
A helpful clock designers aid is a program called "Clockaid" it can be downloaded at
 www.chapter124.com/clockaid.htm
I have found that the program was developed for involute (metal gear) but can be used or modified slightly to accommodate cycloid (wooden gear).

JayRay_Hughes

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Common Clock Gear Trains
« Reply #2 on: September 20, 2005, 05:17:30 PM »
Do you all know of any rules that I may want to apply when choosing gear trains that are not in tradition or the favorites posted in list.

One rule i know about is: Pinion to wear ratios should never ruduce to a ratio of a interger.......

for example:    49:7 ratio will reduce to 7:1 ratio or the integer 7.

The rumor is integer ratios will wear faster.......I don't know if this is true but i will buy it.

Offline rabbit

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ratios
« Reply #3 on: September 29, 2005, 04:48:25 PM »
JayRay-
There are two schools of thought, and I accept both.
With an "integer ratio", the same pairs of teeth (gear/pinion) always mesh on each revolution. With a non-integer ratio, each pass puts a different pair of teeth in mesh. (Some fractional ratios are also called a "hunting ratio" because a given tooth "hunts" the other gear.)

Some say integer ratios lead to "bad" wear, but in fact it can be a blessing with HAND MADE wooden gears. If you cut them with a scrollsaw - or even some machining techniques - every tooth is slightly different. If you cut them like I do, some teeth are quite a bit different! With integer ratios, you can try different timing meshes, and get that "bad" tooth to mesh acceptably with an "equally opposite bad" tooth on the other gear. Or sand one or the other to get a decent mesh. When you get it to work, mark a tooth on each gear and always put it back together with that timing mark. (did that make sense?)
I have also "profile sanded" gear teeth by fixtureing them in my crude depthing tool - a little shallow - and running a piece of sandpaper between them as they turn. This technique dictates the timing marks, because the gears will shape each other to a "perfect fit" (although probably far from a "perfect profile").

A non-integer ratio undoubtedly spreads out any wear associated with an imperfect tooth to the entire other gear. It would seem like this would "reduce wear", but my experience is just the opposite. One really bad tooth can wear EVERY tooth on the other gear (similar to my "profile sanding" above), and can eventually foul the whole mesh. Non-integer ratios require that every tooth be as close to perfect as possible. I know that's what we strive for anyway, but to me wooden clockbuilding is an exercise in dealing with reality: One of my realities is that I can't cut a perfect gear. But that doesn't stop me from using hunting ratios. They're not that hard to get right. If you get "close enough", the break-in wear (if I can call it that) will make every tooth the same.

The bottom line of my rambling is: use whatever ratio works for what you're trying to do. A well-meshing wooden gearset - no matter what ratio - won't wear out for a long long time. I have wooden gears that were made with a hand coping saw and a rasp that have run for years without any noticeable wear. I've read of wooden clockworks, windmills and other wooden-geared machinery running for over a hundred years.

p.s.  the disclaimer: this rambling does not address the EFFICIENCY or ACCURACY of the timepiece!
- rabbit

Offline jrbeall

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Joe's wheel and pinion list
« Reply #4 on: January 03, 2006, 05:53:12 AM »
Joe, are your numbers for 8 day or 30 hr. trains?

JR

Offline panistefanin

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Re: Common Clock Gear Trains
« Reply #5 on: June 05, 2017, 08:06:08 AM »
Excellent post. Thank you very much!!
mybestwestern