reactionsgreenspun.com : LUSENET : Elevator Problem Discussion : One Thread
According to two major manufacturer's layouts, the overhead reactions (loads in the down direction)for basement-machine elevators are about double that of conventional overhead machines, for the same speed and capacity.
Can someone explain this?
-- Ted McG (email@example.com), September 21, 2000
Know how a block & tackle works? Count the rope groups. Add up the forces. When the machine is in the basement there are 4 vertical ropes instead of the usual 2 with an overhead machine. Each rope is tensioned to the weight of the car or counterweight. Each deflection pulley/sheave at the top is being pulled downward by the forces on a pair of ropes, and there are 2 deflection sheaves. So the total downward force on the building structure is approx 4 times the weight of the car.
An interesting sidelight is that the traction machine is being pulled UP by ~2X the weight of the car. So make sure it is bolted down tight.
-- Don Vollrath (firstname.lastname@example.org), September 22, 2000.