(1) The internal brakes are located within the brake drums. Each internal
brake has two brake shoes (1, fig. 4-22). The outer surfaces of the brake
shoes are fitted with brake linings. Each shoe is anchored at one end on
an anchor pin on which it pivots. The other end of each shoe is free to be
pushed out or pulled.
(2) An S-shaped cam (2) on the end of the camshaft is mounted between the free
ends of the two brake shoes (l). Rotation of the cam (2) forces the shoes
(1) out causing the brake linings to contact the drum.
(3) A brake shoe tension spring (3), near the free ends of the brake shoes (1)~
retracts the brake shoes (1) from the drum and holds them in a retracted
position until the brakes are applied.
H871 Brake System Schematic