Planetary Gear Clock

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Tailmaker
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Planetary Gear Clock

Post by Tailmaker »

This is a project that has been sitting unfinished for 6 years. It started out with the idea to build a fully wooden wall clock without rotating axles or bearings, using a differential planetary gear set (a.k.a. Wolfrom Gear). FWIW, the gears are not using the typical involute shape but cylindrical shaped teeth to allow for an easier rolling self supporting configuration.

While that worked reasonably well, the intent was to use a 2-second pendulum with two pawls to drive the serrated seconds ring but I never got that to work reliably. The wooden gears just have too much friction and adjusting the 4-foot-long pendulum got fussy.

I finally gave in and dropped the pendulum idea, using instead a small synchronous gear motor that drives the seconds ring with precisely 3 rpm derived from the 60Hz mains frequency.

Finished clock:
ClockFinished.JPG
Cutting the gears:
DSC00567.JPG
Components finished:
DSC00569.JPG
Gear set back side:
DSC00573.JPG
Gear set front side:
DSC00574.JPG
Short Video:
https://youtu.be/6ij7_hXSDpM
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jfederer
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Re: Planetary Gear Clock

Post by jfederer »

Wow! And here am I, tackling Clayton Boyer's "Solaris" and thinking it's complex!
Joe Federer

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TReischl
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Re: Planetary Gear Clock

Post by TReischl »

Oooooo, that is NICE!
"If you see a good fight, get in it." Dr. Vernon Johns

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TomWS
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Re: Planetary Gear Clock

Post by TomWS »

Very nice job! It looks beautiful AND interesting!

Tailmaker
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Re: Planetary Gear Clock

Post by Tailmaker »

jfederer wrote:
Sat Feb 05, 2022 9:38 pm
Wow! And here am I, tackling Clayton Boyer's "Solaris" and thinking it's complex!
I think it is less "complex" to make than the Solaris. After all, just a handful of gear triplets in a shallow assembly.
Admittedly it took me about 50 times more to envision and design that thing than to build it. While you can easily calculate the resulting gear ratio of a Wolfrom gadget from the gear set's teeth numbers I don't know a way to directly calculate the teeth numbers for a targeted gear ratio. I ended up writing a program to just figure that by trying out the millions of possibilities given some mechanical and dimensional constraints. I used 1:12 for the hours hand and 1:30 for the minutes hand. I did not find any combination to create a 1:60 Wolfrom gear. For that reason, the seconds ring has two 0-59 seconds halfs.
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Creation in Wood
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Re: Planetary Gear Clock

Post by Creation in Wood »

Great gear clock
Thank You
Doug

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Leo
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Re: Planetary Gear Clock

Post by Leo »

LOVE IT!!! :) :)
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Re: Planetary Gear Clock

Post by ozymax »

Another interesting time piece Tailmaker. :)
I think your move to a synchronous motor was a good one.
A few years ago I made a wooden Numerchron clock for my niece and discovered just how good the synchronous motors were at getting a reliable tick over.

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Re: Planetary Gear Clock

Post by Bobtail Farm »

Splendid.

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Re: Planetary Gear Clock

Post by 270mag »

This is exactly what I've been looking for. Did you use the gear maker gadget? Is there a CRV file available?

Tailmaker
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Re: Planetary Gear Clock

Post by Tailmaker »

270mag wrote:
Mon Jun 27, 2022 9:31 pm
This is exactly what I've been looking for. Did you use the gear maker gadget? Is there a CRV file available?
No, I did not use the gearmaker gadget (neither M. Wandel's GearGenerator). These make involute gears that are good for power transmission and low friction loss. The self-supporting gears of my clock need however a constant contact engagement so that they also act themselves as bearings. That was accomplished using gears with cylindrical tooth shapes. Disadvantage of this type of gear is higher friction and the need for very precise machining.

That gear design can be done manually with usual 2d-drawing tools but is a bit cumbersome. So I wrote a little BASIC program to directly generate the g-code for the gear teeth. For that reason I only have .crv files for the functional shapes that are not the gear teeth (holes, cutouts etc.). For the gears I may still have the g-code using a 2mm bit but trying to build another clock with these files would probably be difficult and subject to some failed experiments.
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Re: Planetary Gear Clock

Post by 270mag »

Neat. Thanks.

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