What size pulleys?

I bought a concrete mixer recently at the auction. Anyway, the big pulley was a bit mangled and needs replaced. But I got to thinkin'. There may come a day I need to mix up a batch well away from the nearest electricity. Since I ain't gonna tote an 80 pound bag very far away from the tractor, why not convert the mixer to run off the PTO? I know hooking the 540 rpm directly to the bevel gear would be way too fast. So my question is, what sort of reduction ratio would I need?
 
Dan:

Here, hope this helps.

Doc
a153845.jpg
 
Dan:

I realize that the chart is for much higher speeds than what you have - but it all depends on where you place your decimals. LOL

Personally, If I were going to do something like that, I would go with a double reduction set-up, - a 2" pulley on your PTO shaft & a belt to an 8" pulley with another 2" pulley on the same shaft as the 8", but behind it. Then another belt from the 8/2 to another 8" pulley that is connected to the bevel gear. 540-135 First 4 to 1 reduction, then 135-33.75 for the Second 4 to 1 reduction. Not knowing the size of your bevel gear, you may have to adjust the size of the pulley that connects to it (probably smaller).

Doc
 
You set it up as a ratio, and solve for x. You know the rpm you want, Let's say 100 for argument's sake. Current pulley size/ current rpm as X pulley size/current pulley size, and solve for X, simple algebra. Or just plumb an old car transmission into the drive line, that'll give you 3 speeds to choose from...
 
Actually, dad ran the pto to the bevel gear direct, was meant to be that way. You run the tractor at idle, not full pto speed. Doesn't take any power to run one. What's the pto speed at idle?

Paul
 
To add to what Paul said.

The standard speed for an electric motor is 1650 rpm. A tractor pto at idle maybe around 150 rpm or lower.

So a tractor pto is already considerable lower rpm to start with.

If the pulley on the electric motor is 2 inches and the driven pulley is 12 inches that will give the rpm of about 250 or so.

Measure the 2 pulley diameters and get back to us.

Gary
 
Dan,
I just measured my pulleys. 2" on the motor, 14" on the mixer. 7:1 ratio. So if you have a 1650 rpm motor, it should be around 235 rpm on the top shaft, then the cog will slow it down from there.

Don"t forget if you are going to mix off the PTO you likely will be running at idle, so that will change your calculations quite a bit, versus 540 RPM where your tractor is around 1700-2000 rpm.
You may be closer to 1:1 at idle, versus 2.3:1 (540/235)

This is on an old post WWII Sears & Roebuck that I inherited from the wifes grandpa.

Hope this helps,
Rick
 
For a little more than the cost of re-doing the drive train on the cement mixer, you could buy a small gas powered generator to power the electric motor on the cement mixer.

Carry the generator around on a trailer or in the loader bucket, along with the cement, sand and water used to make the cement. The generator will use less fuel than the tractor will use at idle, and the generator will be availble for other uses, like powering electric saws, drills, pole saw, and lights as you complete your projects.

Be sure to keep a belt in the mixer's drive train, it acts as a slip clutch.
 

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