Fig 1Lift safety gearDrag across to scrub · space plays · ← →−300 ms · 1.00 m/s ↓ · running
Governor rope: runs with the car until the governor grips itFlyweights, rope-grip shoe, safety lever and wedgesHoist ropes, which part at 0 msA car runs down at its rated 1.00 m/s when its hoist ropes part. It falls freely, and the governor sheave turns with it, because the governor rope is tied to a lever on the car. As the sheave speeds up from 64 rpm, its flyweights swing out against their spring. At 1.23 m/s one opens the overspeed switch (motor off, brake on). At 1.32 m/s, 33 ms after the ropes part, the other knocks the trip (set to 1.30 m/s, a little late because the flyweights lag the speed) and a shoe drops onto the rope. The rope stops while the car goes on, so the lever is pulled up and lifts the wedges 12 mm into the rails. From there friction drags them home and the progressive gear brakes the car at 0.6 g: it comes to rest 321 mm below where the ropes parted, 348 ms later, with the rope slipping through the grip. Time runs at one twentieth.