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9 comments
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Join Date: Nov 2007
Posts: 23
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Gear Reduction

08/18/2011 11:23 PM

I am not sure if it was the beer last night that killed the only working brain cell or not but I can't seem to understand this 50:1 reducer. There is a small motor that has a friction clutch unit that you can see is not round. This slides into a flexible tube that is bolted solid to the shaft. On the out side of the tube there teeth that could engage the inside of the outer housing that also has teeth. There is a couple of thousandth clearance between the tube and housing. When you run the motor with the tube on it it will turn very fast in one direction. You can touch it and it stops turning due to the clutch. Now with it turning in one direction and you slide the outer housing on as soon as the teeth engage the rotation of the tube reverses and slows down. I don't under stand the principal of how it revers and slows down. Can some one explain this to my old dead brain. Many thanks.

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#1

Re: Gear Reduction

08/19/2011 12:12 AM

Wonder if your dealing with a planetary gear system, which seems likely it would be for a 50:1 ratio. After everything is reassemble, can you stop the out-put shaft just by touching it? Or is this a trick question??

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#2
In reply to #1

Re: Gear Reduction

08/19/2011 12:31 AM

Allow me to wonder with you. If he takes down that one box, some gears will probably show. I also have seen it just with friction wheels without teeth.

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#4
In reply to #1

Re: Gear Reduction

08/19/2011 2:08 AM

dj95, Not a trick question and no you can't stop the output shaft if is in the housing. With out the housing it can be. What is strange to me is in the housing with just the output shaft and not the motor you can turn the as the teeth just touch. If you apply any pressure to the center of tube end of the output shaft so that it engages the teeth it lock tight. And that makes sense as the teeth on the housing don't move. But when the motor is inserted with just a friction fit to the tube and you start the motor turning clockwise the tube rotates counter clockwise very slowly. If there were gears where there is a solid connection I could understand the reduction via size and also the reversal. Tried to up load a video but this will not take videos. Is this any help?

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#3

Re: Gear Reduction

08/19/2011 1:10 AM

Alas, the picture isn't clear enough to tell exactly what is happening. Nor is the description. The guess about planetary makes sense, though.

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#5

Re: Gear Reduction

08/19/2011 5:54 AM

Look at the HARMONIC DRIVE description and you will find the answer !

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#6
In reply to #5

Re: Gear Reduction

08/19/2011 10:33 AM

I was thinking harmonic drive also but I wasn't sure from the pictures. GA!

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#7

Re: Gear Reduction

08/20/2011 4:38 PM

The "harmonic drive" possibility seems to be a good candidate, but I can't see the flexible element in the picture. It might also be a "cycloidal reducer", such as Sumitomo. Depending on how one parses the terminology, either of these could be considered variants of "planetary."

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#9
In reply to #7

Re: Gear Reduction

08/22/2011 5:10 AM

According to all input about cycloidal reducers they work with an EXCENTRIC shaft and NOT with an eliptic bearing. I would suggest you have a better look at both cycolidal reducers and harmonic drive.

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#8

Re: Gear Reduction

08/21/2011 8:14 PM

Thanks to all. Followed the links and it is a harmonic drive and now under stand how the critter works. Many thanks to all who helped.

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