Main brake = mounted on shaft of the elevator machine
elev. first slowed by dynamic braking of the motor, then brake operates to clamp the brake drum, holding car still at the floor
dual safety system
#1 centrifugal governor or electronic speed sensor = cuts off power to the traction motor and sets the brake if over speed
will usually stop the car
#2 safety rail clamps = actuated by the governor, mounted to bottom of the car, one on each side, clamping the guide rails by a wedging action bringing the car to a smooth stop.
Buffers = oil or spring buffers, placed in elevator pit, not to stop a falling car, provide partially cushioned stop if over travel occurs at lowest level.
Overtravel = occurring down or up sensors de-energize the traction motor and set the brake
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