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# Hypocycloid gearbox for Nema 14/17

by JEdren Jan 18, 2013

### Thing Apps Enabled

Hello, I have been working on a 100:1 hypocycloid gearbox to be connected to a NEMA 23 stepper motor. I have been able to get it running and it is giving me the speed reduction that I wanted, but it is not giving me enough torque. It was only able to lift about 2.5 ft lbs and I was curious if you have tested this gear box for torque, or if there are any factors that you have ran into that may have not let the full torque be exposed. Mathematically it should be giving me really high torques but I cannot seem to get the torque out of it. Anything you can help me with would be great! Thank you, Eric

Its seam that the ratio of your gearbox give 64:1 instead of 56:1

dual ratio the way it work is if gearbox are like this:

9 -> 8 (first gear) 7 (static, move because of first) -> 8 (output final gear)
stage 1 = teeth count (first rotating gear 8)
stage 2 = teeth count (last rotating gear 8)

ratio = stage 1 * stage 2 = 64

Trying to print this today. What do you do about the tolerances? My parts fit together so snugly I can barely get them apart again.

Hypocycloid Gear Test

Hey this is fantastic! and just the solution to a very current problem. I will make a print and test this.

Any chance of a version for m5 output bolt?

Or if you can share your design files I could do it myself (.stl sucks in Rhino...)

I am actually working on a single step (1:8) with a m5 output at the moment.
I use an old academic version of solid edge so I think there might be very few that can read these files... But I will try to at least make a 2d .dxf file of the gears.

Thanks! The 2D would get me far. But actually if you aim to upload the 1:8 design soon I might just start with that.

Any news with the 1:8?

I printed all the plastic parts. I don't have the bearings yet, so can't test it fully. It seems that the gear fits just a bit too tightly and won't rotate freely. I printed a second one at 95% in X and Y. It now seems just a bit too loose. I'll keep playing and see if I can find bearings as well.

Awesome thing! I hope to use it on my dual extruder to reduce the load on the NEMA 14's and keep them cooler (if necessary).

Would it be possible for you to modify the file to recess the M3 heads?

Do you mean in the top case piece so that the heads are flush with the outside?

yes