Fully-functional Hand-cranked Hypocycloid Speed Reducer Model

by otvinta3d Oct 13, 2016
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Saw this in Design World. You beat me to making the model. Nice job!

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I followed your instructions precisely and used the exact screws you specified. Everything worked perfectly. On models that require screws, I usually tap the holes first. It was unnecessary this time.

Secondarily, I have a question about the theory of the thing. Some of the models, designs, and videos show a single disk, some have two. What are the pros and cons of 1 or 2 disks?

This is the 2nd one of your 'masterpieces' I have built (the first was the multi-stage planetary drive). Are there any more?

About the Hypocycloid Speed Reducer: I thought, if I built it and had the parts in my hand, and assembled it, I would understand how the speed reduction occurs ...and... why the input is (say) clockwise and the output anti-clockwise. Wrong! I still don't understand how it works.

Looks great. This was one brilliant invention, no doubt.

I would recommend building our Rubik's Cube solving robot next.

is the gearbox backdrivable? Thanks

No, definitely not.

Is all cycloidal gearbox also not backdrivable or only for this design. I am very like this design, it is very compact but backdrivable is essential requirements for me, could you give some advice. Thanks

Hard to say. Our 3D printed model does not seem to work well when the large wheel is used as the driver, but if it were made of metal, things could be different.

Thanks for letting us know. The guy didn't even bother to make an attribution to us.

Well if it's any consolation that video is why I looked this Thing up.

Oh and he has added this to the description: SHITTY 3D PRINT MODEL ATTRIBUTION

make of that what you will

Please add to the description that this requires countersunk wood screws to assemble correctly. I purchased a pack of dome-head machine screws from Home Depot and they required heavy modification with a hand drill and file to make them work for attaching the cams to the shaft. Alternatively, I feel like the design could be modified to work with printed pins, since the screws simply act as pins anyway. There's no need for threads.

This model requires a few metric M3 Philips-head screws, and that is already mentioned in the description. Wood screws of any kind are not needed. Neither is drilling.

Yes, but the screws have to be wood screws (countersunk head, sharp tip). A machine screw does not work.

All our models use the same assembly hardware, flat-head metric M3-12 Phillips head screws:


and also metric M3 nuts.

Wood screws are not needed, and machine screws work just fine.

I suppose it doesn't need a sharp tip, but it does have to have that countersunk head. Not just any machine screw will work. Perhaps you could add that image to the description?

You are right. The term "Phillips" does not unambiguously describe the screw. We will just add a picture of the screw to the list of pictures to avoid confusion in the future. Love the make, BTW, thanks.

How is the backlash on this gearbox?

No backlash is built into this model.

what's the gear ratio on this?

1:11. Eleven is the number of "teeth" or petals on the cycloid disk, which is less by 1 than the number of pins.