13. A fan is driven by an electric motor turning at 1800rpm. The transmission is done via a flat belt an pulleys; the diameter of the pulley on the motor shaft is 480mm and that on the fan shaft is 320mm. The belt is 100 wide and 3.5 mm thick while the coefficient of friction between belt and pulleys is 0.8. The density of the material of the belt is 1150kg/m and its permissible stress is 12MPa. If the distance between the axes of the shafts is 1400 mm find the power capacity of the belt. Hints: -Find the angles of contact between belt and the pulleys (from diametrs of the pulleys and the distance between axes); -Find the maximum allowable tension in the belt (F1) from the allowable tension and the cross section dimensions; -Find centrifugal force; -Find the tension in the slack side of the belt (F2). -Torque is (F1-F2)r (radius of smaller pulley); -Multyply torque by angular velocity (of smaller pulley) to find power capacity of belt. Note you can also just do: P=(F1-F2)V, where V is the linear velocity of the belt.