RPM for Motorized Mill

How slow is too slow for a gear motor to run my mill? a lot of threads suggest 120 rpm is fine.....but is somethign under 100 rpm manageable?

The proper RPM is really dependent on the size (diameter) of the rollers in your mill. A large roller being spun at the same rpm as a smaller roller is going to move material a lot faster. What you really want to know is surface speed. For example:

A ø1-1/2" roller turning 120rpm has a surface speed of ~565" per minute
(ø1.5in * pi * 120rpm = 565in/min)

If you wanted to match that surface speed with a ø2-1/2" roller you'd only need to turn it at ~54rpm
(ø2.5in * pi * 72rpm = ~565in/min)

You want your drive roller to be under 200, I think mine is at 170ish. Anything slower will just take longer to mill.

Monster recommends anywhere from 150-250 but says you can even go upwards of 300 if you're will to deal with more flour.
I'm running at 250 and don't have any problems.

There's nothing wrong with milling slower. You'll just get a little older waiting for your grain to crush

well i was hoping to find a bodine gearmotor model 0650 or 0651. 170 RPM, 45 in-lb torque or 116 RPM, 68 in-lb torque. However they seem to be in short supply on ebay, but i have found a few that will run at a speed of like 80 RPM........of course that means there is more torque....

but im thinking that is tooo slooow.

Often, the higher the torque, the slower it goes...(there may be some math in there!)

My beast will crush rocks or break the mill trying - but it turns at 62 RPM. so I load up the hopper and go clean equipment.

Like others have said: slower is fine, it'll just take longer.

Also, as I mentioned before the real speed you're worried about is surface area speed, not RPM. You really need to compare RPM, Roller Diameter and Length to get an accurate comparison of speeds. RPM on it's own means little unless the mills being compared have rollers of identical size.

I have a Monster Mill 2-2.0 and have a 80 rpm motor. No issues, and I can mill about 20lb of grain in 6 minutes.

Like others have said it just takes alittle longer to mill. The difference is 3 vs 6 minutes. I would go with whatever is cheapest and the time difference doesn't matter.

I picked up a free 1/6 HP Delco motor that runs at 1725 RPM and plan to use it for my Barley Crusher mill. Will this motor work or should I look for something larger? I've read that I might need a rather large (maybe 12") sheave to get the RPM's down to the right speed.

Keano41 said:

I picked up a free 1/6 HP Delco motor that runs at 1725 RPM and plan to use it for my Barley Crusher mill. Will this motor work or should I look for something larger? I've read that I might need a rather large (maybe 12") sheave to get the RPM's down to the right speed.

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300 is usually the max speed, so the math says -

1750 / 300 = 5.8

you need to reduce your motor speed by a 5.8:1 ratio

a 12" sheave on the barley crusher needs a 2.06" or smaller sheave on the motor.
many larger sheaves don't have 3/8" bores (if I remember correctly, the Barley Crusher has a 3/8" shaft) so you may need to sleeve it.

Keano41 said:

I picked up a free 1/6 HP Delco motor that runs at 1725 RPM and plan to use it for my Barley Crusher mill. Will this motor work or should I look for something larger? I've read that I might need a rather large (maybe 12") sheave to get the RPM's down to the right speed.

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It will work fine. You will need sheaves, yes, if I recall correctly the barleycrushers rollers are 1.5" same as my crankenstein. I run a 10" sheave and a 1.5" sheave.

Edit: See this link:
http://***********/component/resource/article/1171-motorize-your-grain-mill-projects

Edit 2: if you look at some of my past posts I've linked every part you'd need other than motor to make it work, including the sleeve to make the 1/2" sheaves work on the 3/8" mill shaft. When I get near a computer I'll look it up again as well. I should just put them in my signature.

Thanks. I'll give it a try soon and report back.

phoenixs4r said:

It will work fine. You will need sheaves, yes, if I recall correctly the barleycrushers rollers are 1.5" same as my crankenstein. I run a 10" sheave and a 1.5" sheave.

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Where did you pick up your sheaves at?

Keano41 said:

Where did you pick up your sheaves at?

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Grainger

The larger one was expensive, but honestly I'm glad I did it. Tightened the mill down and conditioned my malt. Won't look back.

I have 3 motors for grain mills in classifieds