The pulley wheel used in Pump Aid's Elephant Pump uses an angle iron rim and off set spokes like a bicycle rim. These two features make the wheel considerably stronger. The rim is then lines with two strips of car tyre instead of two rims. Care must be taken to cut the edge of the two strips as shown on the right of the below picture and not like that shown on the left. If the tyre strips are cut as shown on the left the rope does not slip with the normal rope tension due to the sharp (acute) angle.