First let me start off by saying I was a liberal arts major so I need some help with some formulas I've researched. I'm rotating a hollow cylinder that is 8ft in dia. x 8 ft long. The cylinder weighs 3750 lbs and will be filled with 20,093 lbs of watered sewage sludge. Total weight = 23,843lbs. The cylinder sits and rotates on 4 free spinning rollers. The water drains off over a 6 hour period and the remaining dry material weighs approx 6000 - 7500 lbs. I assumed that a drive package with enough torque to turn the cylinder with the full load of watered sludge would also turn the cylinder with the dry material, even though the material has changed and the dry material has an angle of repose that the drive package will have to overcome when turning the cylinder. Any insight or suggestions on that assumption would be helpful. I understand that Torque=Moment of Inertia * angular acceleration Moment of Inertia of hollow cylinder = Mass * r^2 First question: Can mass be expressed in lbs or does it have to be Newtons? As I understand it, there is a difference in mass and weight and I'm not sure how this affects the calculations. Second question: I've seen different ways of calculating angular acceleration. I understand it to be: Ang. acceleration in rad/sec^2 = change in velocity/ change in time * 2(pi) I may be incorrect and this is where I need help. The tank rotates at 0.04 rpm. (yes it's really that slow) and the acceleration time is from 0-0.04 in 5 seconds. Once I determine the torque required I can determine hp and size a drive package appropriately. Thanks in advance!