With all of the steel tanks that seem to have accumulated in the garage (~ 50 between my buddy and I), tank tumbling was becoming expensive, so I ordered about $100 in parts from the Surplus Center and the local home improvement store and built my own.
The tumbler is powered by a surplus Gear Motor, which turns a keyed shaft which has been ground down and covered with vinyl hose. This is the drive roller which turns the tank.
The rollers themselves are basic conveyor rollers on 1/2" cold rolled steel, which has had both ends threaded with a 1/2" NC die. This rod is also covered with some PVC Conduit spacers to keep the rollers in place.
The motor easily handles two tanks at once (either 7 1/4" or 8" O.D.). The two tanks shown are a pair of little HP 80's that had some rust in the bottom from not blowing out the valve prior to filling the tanks.
We generally tumble our tanks with ceramic tumbling media along with some Blue Gold industrial cleaner, which is used for Oxygen Cleaning the cylinders and valves.
After the tanks are tumbled, they are dried quickly with compressed Scuba Air, inspected and the valves are replaced using a little Christo-lube on the threads and a Viton Tank Neck O-ring. Note that the the tank O-rings are static and should NOT be lubricated.
Here is a list of some of the parts I used:
Note: the keyed shaft needs to be turned down on a lathe or ground down to size. See Robert Evans' improved Tank Tumbler for alternate methods for the drive roller.
The motor that I used is no longer available (sold out), but the Surplus Center does have another motor that should work just as well.
The other basic parts were found at Home Depot.
Frequently Asked Questions about building this tank tumbler:
One of the changes I would make in the design if I were to rebuild it would be to support the drive shaft with a Pillow Block Bearing near coupling to the motor. As it runs now, the coupling supports all of the weight of the tanks and tumbling media and that is more stress than it really needs.
I was asked about grinding down the shaft, so I checked my tumbler, and I ground the shaft down to just over 1.25", something like 1 5/16", which matched the ID of the clear plastic hose that I put over it. The outside diameter of the hose is about 1 5/8", so clears the thickest part of the shaft in the center. I have two sections of hose, one near each end that drives the tanks when tumbling.
With the Bodine gear motor above, if you do the math, the final speed of a 7.25" tank should be around 72 RPM. This is just slightly higher than what Global recommends (25-50), but it seems to work just fine. Global states that speeds above 75 are too high. One tumbler like this was built in Oregon using the same motor and a speed circuit was added to slow the motor down, but there was no discernable difference in performance.
For spacing, I just eyeballed a 7.25 OD tank and mounted the shafts on 8" centers. That puts the distance from the rollers to the drive shaft at about 5 3/4", which seems to work well for both 7.25" and 8.00" OD tanks.
For tumbling media we use (20 lbs/tank) of ceramic media that we purchased from Global. It is reusable, and will last for several years (or as often as we use it for a lifetime) before it gradually loses its effectiveness as the edges round down. The "pellets" are about 3/8" in length and 1/8" outside diameter. I understand this type of media is readily available from several industrial suppliers, which means I likely paid WAY too much for!
If you do order the Bodine motor above, the start capacitor and relay are unnecessary. Just wire up the Run Capacitor, plug it in and the motor has plenty of power to start turning two tanks full of media.
Robert Evans built a much improved version of this tank Tumbler. See the results of his hard work here. Craig Miller also built an even better version of my Tumbler, dubbed "Boydski Version 3 Tumbler".