Quote Originally Posted by tonybroad
If you know the torque of your engine you can use

Torque (Nm) = Force(N) x Distance (radius of your pulley in metres)

so Torque/Distance = Force

And if you don't know the torque but do know the power being transmitted, then

Force(N) = Power(Watts) / Velocity(m/s)


Velocity(m/s) = Revs(rpm) x 60 x 2 x pi x radius(m)

Note that the Force derived by either method is strictly the differential tension between the two sides of the belt. If the return side is close to slack then the Force is the RADIAL load on the bearings.

The AXIAL load on the fan bearing is the thrust; on the other end the axial load will be low.