Collected Information on Rock Tumbling
My 31" Truck Tire Rock Tumbler
Last update (this page): March 16, 2008
As mentioned elsewhere, I don't worry about mixing rock types during
coarse grinding. Everything goes in my big tumbler with the 31-inch
tire for a barrel. You can read the (original)
nearby shows the
revised door design
(as of November 2003), including a screw-eye I added to the edge of the
door after drawing up the revised design (grin) to make it easier to
pull it off the "slurry glue" when opening it. This picture shows what
it looks like when the door seal or the rim seal leaks a little! Also
note the supports I had to add after all to keep the tire upright. You
can't see the rollerskate and rollerblade wheels between the supports
and the tire.
nearby is a side view.
nearby, taken without a flash, shows the tumbler in motion.
The tire tumbler, by the numbers:
31x10.5x15 tire = 31 inch diameter, 10.5 inch width, 15 inch diameter
rim (fairly common size, but old style measurement).
1 revolution in 6.3 seconds => ~9.5 RPM => 0.87 MPH => 21
If a tire lasts 6 months, that's ~3800 miles before the inside wears
~204 watts => 4.9 KWH/day => ~34 cents/day for electricity used
for coarse grinding only (usually 30 grit).
Loaded with 2 gallons of rocks, 1 gallon of water, 2 cups of coarse SiC
(silicon carbide) grit => ~3 lbs or $4.50 => $1.12/day.
Total < $1.50/day 4 days per load, typically results in 1 gallon of
rocks ready to polish => ~$6/gallon (or ~12-15 pounds).
"How long does it take?"
Most rocks are done in 1-3 runs; sorted after each run into various
- ready to polish,
- return for more grinding, or,
- give up and toss it in the rock garden
Coarse-ground stones then move to smaller tumblers for fine grit (220),
pre-polish, and polish; one week per cycle, yielding 1 gallon (12-15
pounds) of polished stones every ~3 weeks.
Two, screwed to the inside wall from the outside (between tread
grooves); $1 or so each. These increase tumbling action.
Slurry in a hurry:
~4 gallons of mostly-dehydrated mud per month.