I would also like to make a rock tumbler, like another poster. My plan is as follows.
I will use a used tire as the rotating vessel. I grew fond of used tires after my generator project.
The tire will be bolted to a large plywood ring that will have a hole larger than the internal diameter of the tire, just enough to go a little bit over the widest point of the tire.
There will be a board screwed to plywood and serving as a "diameter" of the plywood ring.
There is going to be a horizontal shaft, mounted in bearings. (see below). The shaft will be made either from a steel pipe nipple, with flanges on both ends, or from a solid 3/4" diameter piece that I already own. On one side, a sprocket will be bolted to the flange. On another, there will be an adaptre plate to attach the "diameter" board securely, but it will be removable for cleaning purposes.
The sprocket will connect via chain to a 3/4 HP 60 RPM gearmotor with a keyed shaft and another (smaller) sprocket. My friend will give me that gearmotor (I gave it to him 3 years ago, but he did not use it).
My expense will be sprockets, nipples and the shaft (maybe).
My question is about bearings. I have a variety of bearings, about
100-150 lbs of bearings. I have some sealed bearings, some needle bearings 1 1/8" ID. Huge stuff for tractors and tanks, tiny ones etc.I also have something I like, spherical bearings 3/4" ID. They are not pillow blocks because they do not have a "base" to be screwed to something. Nevertheless, they are nice because they can survive misalignment. (I also have some 1/2" ID spherical ones, but I need a bigger shaft).
My misgiving about them is that I am not sure what shaft to use. I have a solid steel 3/4" shaft. But how would I mount a sprocket on one side, and a plate holding the wheel, on another? I can easily drill and tap a coaxial hole on both sides. But I have great doubts that the bolt's tension would be enough to hold it during days of operation. I do not have a welder.
I could try to thread both ends on my lathe, but I expect this to become a pathetic failure. And I do not think that there will be a suitable NPT flange at my home improvement store (although I am not sure).
I can probably drill smaller parallel holes and tap them and put in little 8-24 screws or some such.
i