Will 1/4 HP motor work for MM3 mill?

I used a gear motor to motorize my MM3 3 roller mill. It has 40 in/lbs of torque. Not enough. Kept jamming and I've come to find out that this mill requires at least 50-60 in/lbs of torque.

So I'm looking to see if another motor will work. Does anyone know if I'm doing this correctly?

I dug around the garage and found I have a 1/4hp blower motor. I tried to calculate the torque using this formula.

T = (5252 * HP) / RPM
T= (5252 * .25) / 173

If I reduce the RPMs to 173 with a gear box I get 7.59 foot/lbs of torque.

Multiply by 12 and I get 91 In/lbs of torque.


Is this correct?

I'm concerned because it seems like a lot of people suggest you just go for a 1/3HP to 1/2 HP motor. But 91 In/lbs would seem to be good enough, no?

Thanks for the help. As usual, I only find the right threads on here after I make a purchase and then have issues to use as search terms. Gotta laugh.

Cheers.

Sounds like you'd be alright with that motor. But you didn't factor in the loss to the gearing (but you should be okay after that too)

Other people who have gone from a 1/4 to a 1/2hp may have been running a much higher RPM, and therefore not getting enough torque. Remember you could run it fine one a 1/100hp motor if it was geared down enough (it would just take 3 days to mill 1lb), and you could have problems with a 10hp motor is it ran crazy fast.

I think I'm going to keep this motor and go with a 15:1 reducing gearbox. This will give me 115 rpm. With 15% loss from the gearbox I'd still have 116 in/lbs of torque. Three times with I have now.

It's slightly slower, but nothing that should ruin my day and I should have plenty of torque.

I think I'm going to order the gearbox from THIS SITE.

Dgonza9 said:

I think I'm going to keep this motor and go with a 15:1 reducing gearbox. This will give me 115 rpm. With 15% loss from the gearbox I'd still have 116 in/lbs of torque. Three times with I have now.

It's slightly slower, but nothing that should ruin my day and I should have plenty of torque.

I think I'm going to order the gearbox from THIS SITE.

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Looks good to me. 115rpm is about 2 rev per sec, which is at the high end of what a person could turn it at, so that's not too slow.
If you don't already have one, a big hopper would be nice. When doing large grain bills you could just fill it and walk a way.

I have a groschopp gearbox, great deal. I use it on my mm3-2 and couple the gearbox to the mill with a lovejoy spider coupler.

I do wish the mill had a key slot though, i might add one. I went with a 10:1 on a 1/2 HP and the retention screw on the lovejoy couldn't secure the coupler tight enough until some shaft damage "secured" it... i found it when doing some work on the mill and it took me an hour to carefully remove it. doh!

Yeah Dongza 1/4 HP should work fine. I would go for your 91 in-lb vs the 115 RPM. I like that better. My motor is 1/3 hp, 100 in-lb, and 175 RPM.

I am still getting sticking with my mill too though. I'm gonna call Fred again. I've done everything he suggests. Argggh!

Also oustide91219 - I did the same thing. Had to expand the chuck flat on the motorized roller wider so that it wouldn't jump and damage the shaft.

FYI - someone told me (wasn't it you outside?) that Grosschopp is not going to make the NEMA gearboxes anymore. Order while you can. These things are sweet!

A 12lb fly wheel would really smooth the operation of the mill, it's too bad it's not set up for that.

Wish that I had seen this thread yesterday. I just ordered the same motor. Oh well!

SankePankey said:

Yeah Dongza 1/4 HP should work fine. I would go for your 91 in-lb vs the 115 RPM. I like that better. My motor is 1/3 hp, 100 in-lb, and 175 RPM.

I am still getting sticking with my mill too though. I'm gonna call Fred again. I've done everything he suggests. Argggh!

Also oustide91219 - I did the same thing. Had to expand the chuck flat on the motorized roller wider so that it wouldn't jump and damage the shaft.

FYI - someone told me (wasn't it you outside?) that Grosschopp is not going to make the NEMA gearboxes anymore. Orderp while you can. These things are sweet!

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You're right. I emailed grosschopp yesterday and they do not have the NEMA gearboxes anymore. He told me it would be a 6 month lead time to get any.

So I wound up buying a different gearmotor. This one is 130 in/lbs at 72RPM. Slower than I wanted, but oh well.

The issue is, it requires a capacitor. I called Bodine and he gave me the specs. It calls for a 2.7uf/240vac capacitor. I'm wondering if a 3uf/370VAC capacitor will work as that's the closest I can find for now. My understanding is that the VAC rating is the maximum it can take, so 370VAC should still be fine, correct?

I'm not sure about the 3uf vs the 2.7uf, though. Anyone familiar with these things?

Was a pretty good deal, though. I actually got two of these motors (was a package deal) from ebay. so I will likely have an extra motor in case anyone needs one.

ChuckO said:

Wish that I had seen this thread yesterday. I just ordered the same motor. Oh well!

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Hey Chuck,

I just got two brand new bodine gear motors 110VAC from ebay. Came as a package deal for $110. Has 130 in/lbs of torque and 75 RPM. Not the fastest, but if you wind up needing a motor I'll happily send it to you for $55 plus shipping.

I just have to figure out the capacitor on these things, but they should only be like $10. Well, I'll update once I get everything. If your motor doesn't work out, PM me. Don't feel bad. I now have a motor from surpluscenter.com and the 1/4HP blower motor, plus I just bought the two bodines! Better not tell the wifey. This one didn't work out as planned!

What kind of mill did you buy? I've heard the gearmotors from surpluscenter.com are okay for two roller mills.

FYI- I have heard that you don't need CAP start on a gearmotor if it's high enough torque. The cap start will just jump start from off rather than a ramp up to speed. This can be a problem if you have a low torque motor and want to start with the hopper full, but not a problem if you start empty.

I have a GE motor and I can't remember if it has CAP start. I think that info comes from Fred Francis if I remember correctly.

Why did you need cap for that motor?

Dgonza9 said:

Hey Chuck,

What kind of mill did you buy? I've heard the gearmotors from surpluscenter.com are okay for two roller mills.

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I bought a Crankandstein 3 roller mill, so I need the higher torque. I've PM'd you about the gear motor.

Wife already knows about purchase of inadequate motor, so I'm in the doghouse as I write this.

I will probably have an extra gear motor to find another use for in the future.

Chuck