DIY tank tumbler

[Dave in PA]

I am building a tank tumbler based on the Global one. I have a 60 RPM gearmotor similar to the one they use. Everything I have read suggests 45-60 RPM tank speed ideally tumbling. The Global one looks like they use a 2" dia drive roller. That roller is coupled directly to the gear motor, therefore it is turning at 60 RPMs. That would, if my math is correct, give me a 16.5 RPM tank speed, based on 7 1/4" dia tanks. My dilema is that I can use a 2" diameter boat roller for a drive roller (that was my plan) but will that give me sufficient tank RPMs? Do I need to use a larger drive roller to speed up the tanks?

 

[phunk]

Well if there's no gearing between the motor and the roller, then you'd need a roller the same diameter as the tank to get 60 rpm for the tank. Otherwise, with a 2" roller and a 7 1/4" tank, you'll need the roller doing about 215 rpm to get the tank around 60 rpm.

 

[Dave in PA]

Yes, I know that, my question is do I really need a larger drive roller? The most common commercial tumbler doesn't use a larger roller.

 

[phunk]

If your motor is 60 RPM, you either need a large diameter roller on your drive shaft, or you need about a 1:4 gear ratio for your 2" roller.

If the commercial tumbler doesn't use a larger roller, then it uses a faster motor.

 

[captain]

I think the solution to this is to determine what is the best tank RPM and work backwards to determine the size roller needed to attain it.

 

[rcontrera]

For the Global tumbler, the center roller is turning at 60 RPM which translates into about 25 RPM for the cylinder. Even Global's tumbler instructions say that you need to turn the cylinder at between 25 and 50 RPM for optimal results.

http://www.gmcscuba.com/library/Educational%20Bulletins/Repair%20and%20Testing/TANK%20CLEANING%20&%20TUMBLING%20TIPS.pdf