Mill motorizing help needed.

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Plan9

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I'm trying to motorize my Crankandstein mill.
I have a 1/2" 550 rpm drill. I sized a belt and pulleys to step it down to 180 rpm.
I got everything put together and started to test it out.
It's running fine, speed looks good. Drop a little grain in, looks good.
Drop a handfull of grain in, mill binds, drill keeps spinning.
I've tried loosening and tightening the belt, it just spins when a fair amount of grain is in.
I widened the gap, with the same result.

I've hooked the drill directly to the mill and there is no stopping it. The speed is just too fast.

I would prefer to use the pulleys, is there something I'm overlooking to stop the spinning?
 
What are the sizes of your sheaves (proper name for "pulleys" used in belt drives)?
 
Yeah, you've got the smallest possible drive sheave. I'm guessing it's the drive sheave that slips? Switch to larger sheaves, but keeping the same ratio. Larger sheaves = more contact area between belt and sheave = more friction = less likelihood of slippage. Also, your belt tension probably isn't high enough. Push against the belt midway between the sheaves - if they're 12" apart or less, you should barely be able to move the belt.
BTW, the Crankandsteins can be run at 250-300 rpm with no problems.
 
Yeah, I'll probably move the 3.5" to the drive, and pick up new belt and a 8" for the mill.
 
Use moisture to condition your grains the night before. Then speed will be much less of an issue
 
Have you looked into a HTD belt drive system instead? Use it with a short jackshaft suported by a couple cheap pillow bearings with the drill motor on one end of the jackshaft. At the other end a sprocket plus your speed ratio reduction sprocket on the mill with a HTD belt drive. This is a more positive drive without adding extra side loading to the mills 841 oilite bushings.
Check below, sprockets, belt and pillow bearings are cheap from a good bearing supply house. A 25.4mm or 1" wide belt will handle 100# working load, 226# breaking strength per 1/8" of width. Clean, strong, no slipping or oil and wear of a chain drive.
http://www.sdp-si.com/D795/79501012.pdf
 
I think a jackshaft may be overkill with the small speed reduction I'm doing here.
Most guys motorizing mills are stepping down from a few thousand rpm.

I do like the idea of the pillow bearing. I'll probably use a longer shaft with the drill, and support the end with the bearing. That will help keep it lined up.

I'm also going to step up from a 3L to a 4L belt. I think that was a little undersized.
 
I think a jackshaft may be overkill with the small speed reduction I'm doing here.
Most guys motorizing mills are stepping down from a few thousand rpm.

I do like the idea of the pillow bearing. I'll probably use a longer shaft with the drill, and support the end with the bearing. That will help keep it lined up.

I'm also going to step up from a 3L to a 4L belt. I think that was a little undersized.

The added jackshaft was for two reasons, 1st to maintain belt tension in a fixed position, 2nd was to allow the drill motor to be mounted or be supported by the jackshaft. Simple, takes care of two problems plus a HTD belt drive instead for less belt tension on the mills bushing for a longer life.
 
When you mentioned a jackshaft, I pictured a 2 belt system with 4 sheaves. A double stepdown system.
That would have been overkill. :D
 
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