I know the calculations are around somewhere, cause they came with the belt grinder I bought. I just don't know where I put it.

what I am talking about is the calculation that tells you your shaft speed if you are going from a motor shaft at X rpm's, using a pulley of N dia. going to another pulley of L diameter. what is the shaft speed of the shaft pulley L is on. Is that clear as mud?

I have a motor that I think is 1725 rpm's, it is only 1/3hp I think, from a paint sprayer, but it is what I have so I thought I would hang it on a hinge from my table and get a shaft that sits far enough off the edge of the table that I can use maybe a 6" wheel and try to polish with that.

I know that the local bearing supplier would be able to figure it out, but I plan on finding the parts e-bay or junkyard so need to figure it out on my own.

thanks guys.

Red

Motor RPM * Motor pulley Dia/Final pulley dia = final shaft RPM

It's a simple ratio of the pulley dias. If you have a 2" pulley on the motor N, and a 4" pulley on what you're driving L, then the rpm of what you're driving will be N ove L, or in this case, 2/4 or 1/2 of your motor speed.

If you're looking for a certain surface speed, you will need the circumfrance of the driving wheel on your grinder, and to get the distance it will be 2XpiXR, and then multiply that by the rpm of the shaft. Let's say you have a 8" grinder wheel, the circumfrance of that wheel is 2XPiX4(1/2 dia) or in this case 25.1". If you gear down your motor 1:3, you're driving wheel will be turning at 575 rpm (1725 motor) and you're surface speed will be 14,433 in/min or dividing by 60, 241 in/sec.

Red,

Use what you got, but I'll tell you right now that 1/3 hp is frustratingly slow. Take apart an old washing machine and get a 1/2 or 3/4 hp motor. To me 1/2 is the smallest I'd recommend to anyone, unless you put a 4" wheel on it and use it for small stuff.

If you do that, use an arbor like this and you have a cheap setup:

quote:

Use what you got, but I'll tell you right now that 1/3 hp is frustratingly slow

I used a 3/4hp for 6 & 8" wheels.

1/2 is painful, 3/4 is okay on an 8"...

I want a baldor 12"!!!

jeffe

I have another option actually. I have a chinese motor pulled off a Craftsman compressor, it is a 220volt 5hp. 3450rpms. I'll have to figure out a way to mount it and wire it up, but it works (I tested it when I pulled it off the compressor).

I ALMOST setup the Baldor 1.5hp 2800rpm that runs my grinder on a pulley instead of direct connect to the shaft, then I could have rigged it up to run a polisher too. Oh well, too late now.

Red

Jeff, I gave one to a friend of mine. I bet he would talk to you.
Butch