cheap and easy grinder motor speed reduction

[nearbeer]

Thank you for looking at my post. I am trying to come up with a cheap and easy way of reducing the speed of an electric grinder motor. I want to use this motor to turn a homemade muller (to make kitty litter into a good source of bentonite clay). I calculated the diameter of a pulley to get my rpm from 1750 to 60 would be around 21". This diameter would be difficult to come by (I think) and very expensive if I found one.

I have thought about using a speed controller that you hardwire into a router for reducing the router rpm's. Any thoughts?

Bottom line is that I do not have a lot of money to throw at this problem. I have thought about making a large pulley out of plywood but I don't think this will hold up. Your thoughts, comments, and suggestion are greatly appreciated.

In search of my next cold one,

NearBeer

[Al_The_Man]

You did not say if you already have the motor & also the power required? although at 1750 rpm it is most likely a 1 phase 4 pole motor.
If so, your options of speed reduction come down to gearing, rather than electronic speed control, the router versions will not work.
Because they are no longer very polular, one of the cheapest ways is the AC stepper motor, these can usually be had very cheap on ebay and can be run direct off 120vac.
The common RPM on 60hz is 72 rpm.
They often come with gearboxes attached for 8 to 3.5 rpm, if this is not too low, to give significant torque.
Al.

[Andre' B]

Large slow speed pulleys like that can easily and cheaply be made from plywood. Since the circumference is so long you generally do not even need to cut a groove.
I bet it would hold up better then you think, just glue 2 or 3 sheets together to make it 2" or so wide.

[handlewanker]

What's a kitty litter muller? not a Middle Eastern holy man?....LOL.

By bentomite clay I take it you are going to use it for greensand casting?

If so the clay wants to be fine like powder, yes?

I use a liquidiser (blender), (makes vegetables into a puree etc), to make almonds into flour for making almond muffins, and it reduces a cup full of the nuts (used DRY) to a fine flour in about 2 minutes.

This would probably work for the Kitty litter too if that is what you want it for, but the blades might want looking at after a while.
Ian.

[nearbeer]

Hadn't thought of using a blender (liquidiser)...

I was fortunate to be given another electrical motor, a 50:1 gear reducer, and a variable speed motor a few days ago. Haven't had a chance to build my muller contraption (yet) but I think it will be good start.

Thanks Ian for the idea in case mine doesn't work out.

/R,

NearBeer