[mazinsaber]

Hi
I am trying to figure out the way to estimate the power, torque, and rpm for 12v-24v DC motor that I want to purchase to rotate two rubber rollers facing each other. The rollers used to pull weed plants from the soil. The rollers dimensions are 12 in length and 2.5 in diameter each. Thanks!

[ebaines]

You're going to have to tell us (a) the force required to pull the weeds out of the soil and (b) the speed at which the weeds need to be pulled.

[mazinsaber]

Thanks for the quick reply. Basically, the speed is about 0.0037 ft/s, and the pulling force is 0.2248 lbf.

[ebaines]

For a roller that is 2.5 inches in diameter, or 1.25 inches in radius, the torque it needs to apply 0.2248 lbf is T = 0.2248 x 1.25 = 0.28i lb-in. The power required is P = F x V = 0.2248 lb x 0.0037 ft/s = 8.3 x 10^-4 lb-ft/s = 0.0011 watts.

Are you sure of your numbers? You're saying that the roller turns at only 1/3 RPM? Also, 0.2248 lbf is not much force - I was expecting you to say that the forces needed is more like 10 lbf, and the speed around 5 in/s.

[mazinsaber]

Thanks Ebaines again for your reply. Well, the numbers was taken from article, the weed plants they pulled was about 1 in height, so they don’t need too much force for pulling. In my situation the weeds are bigger, but I am still don’t have the exact force for pulling that why I will ask a weed scientist to figure out this situation. I appreciate your help, and I will figure out those numbers. Thanks!