A shaft running at 500 r.p.m. carries a pulley 100 cm diameter which drives another pulley in the same direction with a speed reduction of 2:1 by means of ropes. The drive transmits 250 H.P. Angle of grooves is 40°. The distance between pulley centres is 200 cm. The coefficient of friction between the rope and pulley is 0.2. The rope weighs 1.2 kg/m and has a safe allowable stress of 175 N/cm2. It is recommended that the initial tension in the rope should not exceed 800 N. Find the number of ropes required and rope diameter. Calculate also the length of each rope