In the diagram below there is a hoisting system set up to lift a 1000 lb. unit up a radio tower. This unit is used for painting towers and is lifted using a capstan hoist. As the unit is lifted, it will be tagged with a 6ft. (adjustable) tag line with a pulley that travels up the end of the load line that goes to the capstan hoist. The purpose of this is to hold the unit away from the radio tower as it raises. I am trying to get an idea of how much force the traveling pulley on the tag line will see as it travels up the load line. As the unit is raised higher, the tag line will pull the load line closer to the tower and the ground. This pull will create a sag in the load line and I am having difficulty with calculating the force on the pulley. Do you have any ideas of how to calculate the force on the tag line/tag line pulley?