Question

A lift operates in a vertical mine-shaft to a depth of 600 m below ground level. It has a cage of mass 300 kg, which can carry a maximum payload of 500 kg. The cage is suspended on a steel wire cable 20 mm in diameter. The cable has an effective steel cross-sectional area of 180 mm2 and a mass of 1.64 kg/m. The lift is operated by a winder mounted on a framework 10 m above ground level.

Answer 1

A differential band brake is to be mounted on the same shaft as the winding drum, to slow the cage's descent and to stop it at the 600m level. The rate of descent is to be restricted to 4.5 m/s, and the cage is to be brought to rest at the 600 m level in a distance of 6.0 m. The effective radius of the cable on the winding drum is 1.5 m. The mass of the rotating parts in the last stage of descent is estimated to be around 1100 kg, with an effective radius of gyration of 1.2 m. Hydraulic actuation of the brake lever-arm is proposed.
Therefore;
a) Estimate the required braking torque for the lift.
b) Calculate the torque for the steady descent and stopping conditions.