Grain mill shaft and lovejoy couplings

[Smellyglove]

90 Seconds was a ballpark guesstimate. But I don't think I'm that far off. about 7 KGs @241 RPM (241 is with no load on the motor).

 

[Bobby_M]

Finding a gear motor with enough power is the tricky part. The 2" rollers require quite the torque. I've been looking for a 200 RPM-ish gear motor at 1HP and 120 volts for a long time now.

 

[Smellyglove]

Mine is a 0.5HP with a 6:1 gear ratio built in. I tried sticking some grains in between the rollers before powering up, then it couldn't turn the rollers. But if I do it "normally" (just pour in the grains and power up the motor) it works great.

My motor is three phase/single phase. Just need to rewire it to get single phase. Maybe you should add three phase in your searches and ask if it's possible to rewire it to single phase.

 

[sandyeggoxj]

Mine is a 0.5HP with a 6:1 gear ratio built in. I tried sticking some grains in between the rollers before powering up, then it couldn't turn the rollers. But if I do it "normally" (just pour in the grains and power up the motor) it works great.

My motor is three phase/single phase. Just need to rewire it to get single phase. Maybe you should add three phase in your searches and ask if it's possible to rewire it to single phase.

Where did you get the motor? I'm shopping for one too.

 

[AnOldUR]

The 2" rollers require quite the torque.

I'm guilty of thinking of mill speed in terms of RPM when I should be thinking surface speed. A 2" roller will crush grain almost twice as fast as a 1-1/4" roller at the same RPM's. It's the surface speed of the roller at the grain contact point that's important, not the roller's shaft RPM. If we're saying that 200RPM is good for a 1-1/4" roller mill like a Barley Crusher, than around 125RPM will give you a similar crush and crush rate with a mill having a 2" roller. The same HP motor can be used in either case because the additional torque required by the larger roller is offset by the mechanical advantage gained by using a gearbox or sheaves to reduce the surface speed.

 

[Bobby_M]

That's true. To date, the only thing I ever used for my 1.5" crankandstein is my dewalt cordless on "low speed" which is listed at 575 RPM. I'm sure the load pulls that down a little, maybe to 450rpm. So, 1.5*3 is 4.5" of travel per revolution x 450 for 2025 inches per minute.

Since 2" * 3 = 6, 2025/6 = 337 RPM

While I do want my shop mill to make good time, I'm also considering the dust impact of running it fast. I figured 200 RPM would be good then. Finding a 200 RPM motor that still pulls over 100 inch pounds means 3/4HP or more (I'm pretty sure). I've seen some nice small motors listed for 140in/lb and then see that it's geared to 20 RPM. Great.

PS: yes, I'm aware I'm calculating with pi rounded down to 3. I'm building a Timex, not a Rolex.

 

[Smellyglove]

Where did you get the motor? I'm shopping for one too.

I'm living in Norway, EU so I guess it won't help you much. But I found one on what would be CG for you guys.

As a (a bit funny sidenote) I found a guy who has over 40 metric tonnes of motors stowed away in almost every corner in his house, yard, garage, shed and you name it. Picture an Emmet Brown from Back To The Future, but with motors. An eccentric guy. After about 30 minutes about motor-talk, which I know nothing about, I sort of hinted that I should be going by getting back into my car. Mr Brown here didn't stop talking so I had to roll down my window (after I startet the engine) and continued to talk with him as I was slowly pulling out of his driveway as he walked by the car almost sticking his head into my window. Great guy.

 

[Smellyglove]

I'm guilty of thinking of mill speed in terms of RPM when I should be thinking surface speed. A 2" roller will crush grain almost twice as fast as a 1-1/4" roller at the same RPM's. It's the surface speed of the roller at the grain contact point that's important, not the roller's shaft RPM. If we're saying that 200RPM is good for a 1-1/4" roller mill like a Barley Crusher, than around 125RPM will give you a similar crush and crush rate with a mill having a 2" roller. The same HP motor can be used in either case because the additional torque required by the larger roller is offset by the mechanical advantage gained by using a gearbox or sheaves to reduce the surface speed.

So how fast am I actually milling if my motor is 241RPM (don't mind the load) and I have 2" rollers? Should I get a slower motor, in a perfect world?

Sorry, but I suck at math. A thirdgrader would out-math me.

 

[AnOldUR]

That's equal to about 380RPM with a 1-1/4" roller mill. Still a reasonable number. To a large extent, it's about how happy you are with the results of your crush. Too fast can shred the husks and effect lautering.

The earlier discussion had more to do with HP requirements and that larger rollers will require a higher horsepower motor for the same RPM at the roller. If you're not stalling you mill, you're good.



edit to answer your question:
You're milling at about 125 SFM
(Is my machinist is showing through? :cross

 

[Smellyglove]

That's equal to about 380RPM with a 1-1/4" roller mill. Still a reasonable number. To a large extent, it's about how happy you are with the results of your crush. Too fast can shred the husks and effect lautering.

The earlier discussion had more to do with HP requirements and that larger rollers will require a higher horsepower motor for the same RPM at the roller. If you're not stalling you mill, you're good.

But I'm doing a 2" roller mill.

Nevertheless. I'm happy about it, it's giving the same results as my LHBS which I used for about a year and half. They have a six-roller. Doesnt mean much to me other than my calculations when it comes to crush and extractions are more or less the same, gives med me maybe 1 or 2 points on the good side. I'm just happy I'm saving a fortune (after the mill, motor, gas expenses for the car driving to and forth the LHBS , etc has been "paid down", which will take my whole lifetime, but still). I'm rolling stock MM-setting. The LHBS cost at getting it crushed there is about 20% extra.

I''ve been so happy with the crush (even though it's finer than I expected when buying own mill and motor) that I don't feel the need moistning the grains to get more intact husks. If I feel I need softer crush with the current setting I can always moist the grains before crushing.

 

[Bobby_M]

Maybe it will help someone else trying to do this, but with my MM2-2.0, I tested that it takes about 17 revolutions to run 1 pound of grain through. I tried to maintain a constant 60 or so RPM but it's hard with a drill. I counted out 17 turns. Even if you round it up to 20 revs per pound, that's 3lbs per minute at 60 RPM. A 12 pound grain bill in 4 minutes at 60 RPM or 3 minutes at 90 RPM. Since I have a big ass hopper, I can let it run.

 

[AnOldUR]

:cross:

 

[Smellyglove]

that's equal to about 380rpm with a 1-1/4" roller mill. Still a reasonable number. To a large extent, it's about how happy you are with the results of your crush. Too fast can shred the husks and effect lautering.

The earlier discussion had more to do with hp requirements and that larger rollers will require a higher horsepower motor for the same rpm at the roller. If you're not stalling you mill, you're good.



Edit to answer your question:
You're milling at about 125 sfm
(is my machinist is showing through? :cross

sfm?

 

[AnOldUR]

sfm?

Surface Feet per Minute. It's the rate that the surfaces pass each other at the contact point measured in feet per minute. In this case it's based on the circumference of the rollers, but one object could be stationary.

 

[Smellyglove]

So I'm actually at double speed of what's recommended. Damn that I didn't think about physics before I got the motor.

 

[AnOldUR]

Lot of people run them that speed and faster using a pistol drill. If you're happy with your beer and your lauter, there's no need to change it.

 

[sandyeggoxj]

I'm living in Norway, EU so I guess it won't help you much. But I found one on what would be CG for you guys.

As a (a bit funny sidenote) I found a guy who has over 40 metric tonnes of motors stowed away in almost every corner in his house, yard, garage, shed and you name it. Picture an Emmet Brown from Back To The Future, but with motors. An eccentric guy. After about 30 minutes about motor-talk, which I know nothing about, I sort of hinted that I should be going by getting back into my car. Mr Brown here didn't stop talking so I had to roll down my window (after I startet the engine) and continued to talk with him as I was slowly pulling out of his driveway as he walked by the car almost sticking his head into my window. Great guy.

Ah yes, Norway! My ancestors hail from Norway.

I would like to meet that guy!! I keep checking my local classifieds hoping to score a motor. Someday.

 

[Smellyglove]

Ah yes, Norway! My ancestors hail from Norway.

I would like to meet that guy!! I keep checking my local classifieds hoping to score a motor. Someday.

You'd end up a bit wiser when it comes to gears. For instance that some excavators only have 60-90 HP engines, but with all that gear reduction they are able to lift stuff clocking in at over two metric tonnes.