Motorizing a grain mill - would this work?

I've a 1950's wood lathe. It's powered via a belt to a 1/2 HP capacitor motor. On the motor and on the lathe there is a nest of 4 pulleys. The belt is on a 1'' pulley on the motor and, up top, the belt goes around a 3" pulley on the lathe. This reduces the speed of the lathe from 1750 to 1/3(1750) = 583 rpm.

OK, the plan is to run a second belt from a 1" pulley on the lathe to a 1 7/8" pulley on the grain mill. The speed will therefore be reduced further to 1/1.875(583) = 311 rpm.

I'm pretty sure my math is correct but I'm a bit worried about the set up. Does it sound feasible? I mean, I wouldn't want to knacker the bearings in the lathe or anything.

Cheers!

I'm just going to mark this spot till the morning when I can do the math. I think you will be increasing the speed in the second step. You are going from 1" to 3" to 1" to 1 7/8?

iaefebs said:

...till the morning when I can do the math...

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Ha!

Yeah, from 1" to 3" to 1" to 1 7/8.

Wouldn't ya know it. There is a problem with rotation. The nested (is that the right word?) lathe pulleys are only accessible from the back. That means if I hook up the grain mill from the back it will turn in the wrong direction. Dang! It's never easy, is it.

Cheers

Turn the mill around and the direction of rotation will be correct.

Are you mounting the second 1" pulley in the chuck?

In the 1st step from 1" to 3" you are correct it will reduce the rpm to 583. In the second step you are going from 3" to 1" which will increase the speed back to 1750. 3rd step is from 1" to 1.875" which will take you to 933 rpm.

iaefebs said:

In the 1st step from 1" to 3" you are correct it will reduce the rpm to 583. In the second step you are going from 3" to 1" which will increase the speed back to 1750. 3rd step is from 1" to 1.875" which will take you to 933 rpm.

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How could you use the 3" pulley twice?

bja said:

How could you use the 3" pulley twice?

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I believe the 1" pulley is connected to the 3" pulley; see the picture above. I think the OP's concept is valid in terms of reduction but may have hit a snag on direction of rotation. Question I have relates to the math - does one calculate increase/reduction based on diameters or based on circumference of the pulleys? I'd have thought circumference but it seems most use diameter.

Hamaki said:

I believe the 1" pulley is connected to the 3" pulley; see the picture above. I think the OP's concept is valid in terms of reduction but may have hit a snag on direction of rotation.

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Though I may not have been clear, this was my point. Turning the mill 180* will solve the direction issue.

Question I have relates to the math - does one calculate increase/reduction based on diameters or based on circumference of the pulleys? I'd have thought circumference but it seems most use diameter.

Click to expand...

Either will work but using diameters are easier.

Having a twist in the belt will reverse the direction of turn of the pulley.

Thanks for the replies.

Bja,
I've just ordered the JSP BareBones Mill:




Unfortunately, it doesn't look like turning it 180 will help - looks like drive shaft only extends on one side only. (Unless, of course, I can unbolt the whole thing and reassemble the shaft on the other side)

iaefebs,
Yeah, sorry for the confusion. That "pulley spindle" is one piece, so if the 3" pulley is turning at 583 rpm, then so is the 1" pulley.

Hamaki,
Yes, I believe using circumference is correct, but the pi's cancel out, so you can just use diameter:

Speed of A pulley / Speed of B pulley = (pi * d) of pulley B / (pi * d) of pulley A

flars,
Wow. twisting the belt. Never heard of that before. I'll give it a go!

Cheers!

flars said:

Having a twist in the belt will reverse the direction of turn of the pulley.

Click to expand...

Do you have room below to flip the motor?

check out the wiring diagram on the motor. Some motors can be rewired to run the opposite direction.

Octavius said:

Thanks for the replies.

Bja,
I've just ordered the JSP BareBones Mill:
View attachment 194736

View attachment 194737


iaefebs,
Yeah, sorry for the confusion. That "pulley spindle" is one piece, so if the 3" pulley is turning at 583 rpm, then so is the 1" pulley.

Cheers!

Click to expand...

I saw that after my post, when hamaki mentioned it. I missed the picture. Sloppy help on my part. Twisting the belt is one option, How is the shaft attached to the drive roller on a malt mill? If it is threaded in then you will be unthreading running in the opposite direction. If it's one piece than you shouldn't have a problem. By looking at the picture it appears that when flipping you might need to make some spacers.

The formulas I used for setting up a table saw. Horse power of the motor will be the limiting factor.

D = diameter of pulley on motor
d = diameter of pulley on mill
Um = revolutions of motor spindle
Uk = revolutions of mill

D = d x Uk / Um
Uk = D x Um / d

MrNatural,
Don't really have room below to move the motor. But - good thinking!

iaefebs,
Don't know how the JSP mill is built - I'll start another thread, asking JSP owners.
Not sure I understand you about making spacers - could you elaborate a bit?

bja,
Yeah, I took the motor apart and, to be honest, I don't want to mess with the wiring. I was always useless at soldering.

Cheers!

Octavius said:

MrNatural,
iaefebs,
Don't know how the JSP mill is built - I'll start another thread, asking JSP owners.
Not sure I understand you about making spacers - could you elaborate a bit?
Cheers!

Click to expand...

When the manufacture machines the rollers it is easier to make the drive and driven rollers the same. Then they will tap and thread a hole on one side of a roller to have the longer shaft needed to attach a hand crank or motor to. The thread is made so that the shaft is always moving in the direction it would tighten. When you flip it over and drive, it will try to unscrew itself.

The spacers are necessary because the rollers are not located on the center line of the mill. The distance from the grain enter side is greater than the exit side. When you flip it over, the exit side is up and to close to the hopper. You will have to shim it up. None of this is a deal killer. I had to do it to my direct drive mill because it ran best in that rotation.

iaefebs,
OK, now I get it. Many thanks!

Since, the grinder is attached to a table and being driven by a lathe, are you fastening the table to terra firma? Certain belt tension will be needed in order to keep the belt from slipping when torque increases. How will you adjust tension? Will you have to move the table to adjust tension? Is the table heavy enough to absorb the torque and tension without moving or flipping over, when the lathe is turned on with a hopper full of grain? Maybe, call a local heat/cool contractor or junk yard. They might have a 110 volt, belt drive blower assembly from a furnace laying around. Get the motor and cradle, it will have a belt tensioner mounted to it. The motor might be reversible. I have the adjustable JSP and use a drill. Instead of using a table, I bought two pieces of 3/4" aluminum angle from HD. Drilled the angle to match the threaded screw holes in the bottom side of the end plates of the mill and screwed the mill to the angles. I set the angles across the top of the mashtun and grind right into the tun..... In my application, it is leaner and better feng shui. Just a few thoughts. Good luck with your build.

Vlad, Thanks for the post.

Good point about it tipping over unless done correctly. I haven't started thinking yet about that aspect.

Maybe I should just bite the bullet and buy a 12" pulley from Grainger. I do have another motor (that is reversible!) but it is only 1/4 HP. Would that cut it? A dedicated table, holding both the motor and mill, yin and yang, would be a bit safer.

Cheers!