"SteveB" wrote: I want to make a roller for a 55 gallon plastic barrel to
mix up potting soil. It doesn't have to be huge, and it won't be turning a
lot of weight.
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The weight will not be centered unless the drum is completely full or
completely empty, so may take quite a bit of torque to get it moving.

I have another suggestion: Hang the drum from two V-belts. Drive the
V-belts with two small pulleys on a horizontal shaft. That will give you
quite a bit of speed reduction. If you drive the shaft with a V-belt from a
motor shaft, you can get whatever further reduction you find you need.
Total cost should be moderate.