I built one years ago but it worked OK.

First I built a rectangle from Bed Frame angle iron. I mounted two
self aligning bearings at each of the short sides to hold 5/8 inch rod
parallel to the long sides. I made a couple of pulleys from some two
inch solid round bar and put one on each piece of 5/8 rod at one end.
I ran a heavy duty O ring (From some form of Caterpillar Dozer) on
those pulleys.

I mounted an old washing machine motor under the frame and welded legs
to the frame so the motor was not on the gound. The motor had a 3 inch
pulley and it drove an 8 inch? pulley attached to one of the 5/8
rods..

I used the commercial plastic barrels as they lasted forever and
weren't too expensive. The rectangular frame was long enough to run
three barrels at a time.

I only used self aligning bearings as a mate gave me them and the
housings. The 5/8 rod driving the barrels gave a really large amount
of downwards gearing.

Bob T (in Kojonup WA)

On Thu, 19 May 2005 09:16:33 -0500, Rex B wrote:

One standard 5- or 10-gallon propane tank, empty, flushed etc
Cut a square door in the side, hinge it, add a hasp or something to keep
it closed.
Line it with rubber sheet, held with good contact cement. The spray
bedliner might also work, you can get in in aerosol cans at any parts store.
Support it on a "Vee-block" of 4 inverted wheels - the stationary ones
that are used with casters.
2 additional angeled wheels at the ends keep it from moving axially.
Any small electric motor with a very small-diameter pulley on it.
Belt runs around the outside of the tank between the door and the top
(or bottom). Use a long thin flat serpentine belt. Might need a simple
spring tensioner.
Add rocks, carborundum power.
You'd probably want to tape the door after filling to make sure you
didn't leak carborundum all over the place.
- -
Rex Burkheimer
WM Automotive
Fort Worth TX

Christopher Tidy wrote:
Hi all,

When I was about 8 or 9 years old I really, really wanted a stone
polisher. I think they were rather expensive and also (probably wisely)
my parents thought that I would be bored having to wait months for
results, so I didn't get one for my birthday. Anyway, I woke up in the
night and it occurred to me that a stone polisher (or rock tumbler as
some people call them) would make a great home shop project.

I figure I can make a drum (probably cube-shaped) from welded 1/4"
plate. The drive is going to be more of a challenge (I don't have a
great deal of cash to spend on this). I reckon I probably need about a
30 rpm drum speed and 50 W of power for a small polisher. But the drive
needs to be sturdy and energy efficient if I'm going to leave it running
in the shed all year. A mulit-stage belt drive will be fiddly and
probably not very energy efficient. It seems to me that the best
solution would be an oil-filled worm and wheel gearbox, but I'm not sure
where to scrounge one from. Can anyone think of pieces of industrial
equipment which use a suitable gearbox, which I could look out for in
piles of junk etc? Has anyone built one of these before? Any ideas would
be welcome.

Best wishes,

Chris