Need Help

[Sean Murphy]

I have a steel drum which I use to tumble gravel and other items in. It is 14' long and has a diameter of 5'. We rotate the drum at approximately 30 to 40 rotations per minute. The drum itself weighs around 2 tons and the material inside is roughly 1/2 a ton. The drum sits on 4 wheels (two on each end). There is a chain welded to the middle of the steel drum and underneath is a motor with a sprocket bolted to the frame that the tumbler sits on. This motor is currently a hydrulic motor of which i have no idea how big because its very old and the plate and information on the motor is gone. With the information presented is there a way to figure out what HP motor i need to turn this drum (which has little friction) at 30 to 40 rotations per minute.
tumbler3.jpegtumbler2.jpegtumbler1.jpeg

[jboggs]

Not considering friction, the torque you will have to produce comes from the fact that the mixing action requires the mass inside the drum to rotate to an off-center position before it falls back on itself. That torque would be the product of the weight of the internal mixture and the HORIZONTAL distance to the vertical line along which the CG of the mass lies. It is the same effect you see after you stop mixing. The drum tries to rotate backward until the CG of the internal mixture is at bottom dead center.

If you know the density of the mixture, careful observations during mixing should enable you make a good estimate of the approximate cross sectional shape of the mass, and from that you could calculate the CG. Be sure to consider effects of maximum and minimum charge loads. Both the weight and the torque arm length will be affected by that. Add in a factor for friction, safety, (and then double it for good measure) and you should be good to go.

[Sean Murphy]

Thanks for the help