Treadmill motor shaft.

J81

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I’ve just wired a treadmill motor to a speed controller.

I want to connect a 150mm sander backing plate to the shaft, but I'm not sure what type of shaft it is.

It looks threaded, but it isn’t?

What would be the best type of coupling?

Thanks.
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If you don’t want to use the poly-V belt like original, then make a hub to press on or slide on and retain with a set screw?
 
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If you are making the disc backer, I would integrate the hub @jwmelvin suggested so that you only have a single assembly to balance and true to the shaft. Please post more images as you progress!

And welcome to H-M!
 
I’m building a direct drive tumbler.

It’s trial and error. First time doing something like this.

Im not sure if the motor will have the required torque at low speed. So I might have to go belt driven.

I wasn’t sure what that type of shaft was called. Poly-V is new to me

I was planing to use something like this, but I thought set screws required a flat section on the shaft.FDFB79F9-415C-41BE-B4D3-BE669B8B6D90.jpeg
 
That should work well. If you experience slipping with the set screw on the shaft as it is, you can always add a flat to increase the torque capacity.
 
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I admit I probably have the least knowledge in this area of anyone on the forum. Total novice.

I was proud when I took the treadmill apart and salvaged the motor :)
 
Use of a flex coupling like you depicted will require that the driven shaft have well supported bearings. That type of coupling is used to compensate for misaligned shafts. Depending on your design, a rigid coupling might serve you better.

Based on your comment above, I would assume that you don't have a well equipped machine shop. More than likely, a lathe would be required t make a "close fitting hub or coupling as the likelihood of the poly-V pulley being a diameter that would fit standard bore diameters is small.

Also, my understanding of how a tumbler works, the rotation has to be a low enough rpm that the tumbling media can fall due to gravity, thus mixing the media a parts (vis. a front load washing machine or cement mixer). Too fast and the centrifugal force will just keep the media pinned to the outside of the drum. (One can calculate the maximum rpm fairly easily, depending on your drum diameter.) My guess is that you will probably want something like 50 rpm. Most treadmill motors have a rated speed of around 4,000 rpm which would be an 80 to 1 reduction. As you surmised, this may require some means of mechanical speed reduction in order to achieve your desired speed.

A small gear box would be my choice as it is difficult to obtain large speed reductions with a single pulley arraignment. I would suggest maybe the front end of an old drill or similar. Drill or drill/driver motors operate at similar speeds and are geared down to usable speeds at the chuck.
 
Front end of a drill is a great idea!

I had a quick look at gearboxes but they were expensive and I didn’t know what I was looking at tbh.

Would something like this work?
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I now realise how idiotic my previous post was :)

How would I connect the motor shaft to the gear box?
00E8DAB6-0DCD-41E2-A8EF-203318DDF014.png
 
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Do you already have the tumbler tank / setup? If so, would you kindly post a picture of it?
 
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