Portsmouth Block Mills in 1808. The machines were of 22 types and totalled 45. They were driven by two 30 hp (22.4 kW) steam engines. The machines included circular saws, pin turning machines and morticing machines. With these machines 10 men could produce as many blocks as 110 skilled craftsmen. A pulley-block has four parts: the shell, the sheave, the pin for locating the latter in the shell and a metal bush, or coak, inserted into the sheave to save wear between it and the pin. Blocks can vary in size and in the number of sheaves. The process of making the shells
Elevator poor energy efficiency. Gearless traction machines are low-speed (low-RPM), high-torque electric motors powered either by AC or DC. In this case, the drive sheave is directly attached to the end of the motor. Gearless traction elevators can reach speeds of up to , A brake is mounted between the motor and gearbox or between the motor and drive sheave or at the end of the drive sheave to hold the elevator stationary at a floor. This brake is usually an external drum type and is actuated by spring force and held open electrically; a power failure will cause the brake