Hello, I'm trying to size a motor for an application that I'm working on. The application involves winding paper with two motors. One motor will unwind and the other motor will rewind. However, I'm trying to figure out what the motor power rating should be. Here's the worst case scenario: Very non-elastic paper, winding to a diameter of 15 inches, at 15 lbs of tension at 50 feet per minute. Here is my thought process, and I would like to know if anyone can pick out any incorrect assumptions. As the paper is rewinding, the diameter will get bigger. However, because this diameter is get bigger, that means that it will take less revolutions per minutes to obtain a constant tangential speed (feet per minute of paper). In other words, as the diameter of the rewinding paper grows, the RPM of the winding motor will slow down. Theoretically, this motor should operate at a constant power consumption. This is due to the fact that at a small winding diameter, the motor will not have to supply a lot of torque, but will have a large rpm to obtain the 50 feet per minute tangential speed. But once the diameter grows larger, the RPM will decrease but the torque has to increase since the tension force is further from the center of the motor shaft. Using the formula that Horse Power = Ft-lbs X RPM / 5252, let's calculate the power when the roll is 15 inch diameter. The torque required would be 15 lbs at 7.5 inches. This would equate to 9.375 foot-lbs. To achieve a tangential speed of 50 fpm at 15 inch diameter, that would be 50 /( 2 x pi x (7.5/12)). The 7.5/12 represents the radius in feet. This would equate to 12.739 RPM. Putting this into the horse power formula, this would require .02273 horse power. But my question is, is this number fair enough to determine the power rating? If the motor is accelerating, obviously it will require torque to accelerate it. However, if the motor is moving very slowly and accelerating very slowly, this should be a small force. So my questions are the following: Are the assumptions I made above correct? .02273 HP seems very low. And what would be an appropriately sized motor?