Cycloidal RPM reducer 15 :1 for TT gear motors.

[robothut]

SO all the new Pro robot dogs and bi peds has had me wondering how they are doing the gear boxes on the motors these days Then I remembered a gear motor I had back in the 1980's that was government surplus and when I opened it up there were no gears just this funny lobed ring that some how moved around inside. Turns out there are several version of this gearless gear box and they have advantages over normal gears. For one they can be made smaller. They can be made with no backlash "slop". They can not be back turned, so positions can be held with out using power They run silently and as it turns out they can be 3d printed so much easier than gear reducer units.  Some times they are called Hypocycloid or cycloidal or even wobble drives. They are related to Harmonic reduction units and Strain wave gear drives.

Here is a you tube on a simple 12 too 1 cycloidal drive I designed that is designed to work with a TT type gear motor. So when using the fast RPM TT gear motor that runs close to 60 RPM at 3 volts no load you can now have a 5 RPM output speed for sequenced control or what ever in a small inline design that has few parts.

 

[robothut]

Here is the unit assembled.

[robothut]

I will show a basic toy design that can use this function soon. Here is the insides.

[robothut]

The STL files are on thing-I-verse "I hope, you never know with thing-I-verse".

https://www.thingiverse.com/thing:4444667

[RoboDerby]

I already said it in a YouTube comment. But I’ll say it again. Frickin’ brilliant John!

[ROBODUDE]

AWESOME !!!!

[Andyman]

Such a simple design yet very effective.

[Brian..]

Very clever, John.  When I took my electric screwdriver apart, this was what I found inside. It puzzled me no end. I wonder how thin the housing can be made? And how small the diameter? Anything to tame those cheap yellow motors. 

 

How did you manage to suppress the wobble from the mechanism? 

[robothut]

The diameter would be set by the number of Lobes in the housing and the quality of your 3d printer. I went with a 40mm outside diameter and 12 lobes and that could be printed by any 3d printer. I have a version with 21 lobes in the same size housing that I will play with soon. As for thin, yes it could be made about 1/2 and thick as the one I made, I was just taking advantage of the long drive shafts from the TT gearmotor and a few other things and made mine beefy. You could adapt it down to the smaller N type gear motors . But as is it already takes up less space than a flat gear set up would to give you a 12 second per rotation speed with the fast TT motor. The slower TT gear motor would give you 24 to 30 seconds per revolution on 3 volts, making for a nice sequencer for multi action robot designs. Also ball bearing can be added to the shaft and the off center drive cam and output part, but for the simple toys we built I do not think there would be a reason to do that.

[Golddalek]

preety coOL...many ways to make a mouse trap...I like it.Way to go John.,!