Friction Force of Rotating Shaft

[calypsoman4]

I'm analysing the forces on a vacuum roller brush in an effort to determine the power and rpm's that will be required of an electric motor to rotate the shaft. At anyone time there will be three contact points with the bristles to the carpet. Assuming we want the roller brush around 5000 RPM, what is the maximum friction that would be felt? (assuming nylon bristles) How much Torque would need to be applied to shaft to keep it rotating when in contact with the carpet? (this is a design problem so all dimensions are up to me just having trouble on how to represent this situation.)

 

[swraman]

well you know the torque put on the shaft y the bristles will be the (frictional force) * (radius of shaft). you know what the radius of the shaft is, but you have to somehow estimate the frictional force between the carped and the nylon bristles.