tumblers and the electricity they use cost money. so does the grit. now suppose you cut those costs, you might use sand, but a guy on yt did a year long run with sand and never got a polish, but burnishing did, as would a tiny bit of polish, we may think.

so a half gallon juice bottle, no pillow blocks though i am getting some. running thread goes through the wood and that's the bearing. friction tape over the fuel hose because it slipped. you can see my tail is too small or on too short a stick.

i am thinking the best setup would link the two shafts with a pair of o ring pulleys to make the drum turn easier. on the end the cap turns the tightening way. a well placed cheap ball bearing from ebay would be nicer. the 4 bearings, you can buy just the bearings for like $6 without the pillow blocks, and you would then drill a hole for each, not all the way through so the bearing is trapped, and a screw to block it coming back out.

i found some nice little quartzite and such in some driveway pea gravel, and they would look cool on top of the soil in a potted succulent, eh? the little fan was supposed to help the idle shaft turn, but it did not work.
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https://www.youtube.com/watch?v=eSrYVauOCG4