Cross section of pulley1, pulley2 , pulley3 and pulley4 are as shown in figure. Center of Pulley 1 and pulley 2 are placed on same horizontal line. Center of pulley 1 and pulley 2 are fixed. Pulley 1 and pulley 2 can rotate about their center. Center of pulley3 and pulley4 are also placed on one horizontal line. Pulley 3 and pulley 4 can also rotate about their center. Center of pulley 3 and pulley4 are joined with one stationary plate.Pulley 3 and pulley4 are simply supported on pulley1 and pulley2.Now we apply some load or weight on stationary plate. Finaly this force is applied on pulley 1 and pulley 2 in vertical downward direction because pulley 3 and pulley4 are simply supported on pulley 1 and pulley2. Tangential componants of these force helps to rotate pulley1 , pulley2 , pulley3 and pulley4. If you want to remove pulley3 and pulley4 , stationary plate is directly simply supported on pulley1 and pulley2 then also pulley1 and pulley2 can be rotated.Pl visit http://www.energyefficiency.zoomshare.com/