I am interested in determining the radial force on the contact surface of a pulley and a flat belt under static tension. Can't find anything in the handbooks. Appreciate any information available.
If the pulley is truly static, then the radial force is twice the belt tension.
If the pulley is rotating under load, then calculate torque associated with load (T = 5250*P/N where T in ft-lbf, P in hp, N in rpm) and convert torque to force based on pulley diameter, and multiply be a belt factor.
Here is a reference with belt factors for various configurations. You may find some lower numbers in other references (I know many people use 1.5 -2.0 for Vee belts)