Combined Hydraulic/Lever Rear-wheel Shoe-expander
Combined Hydraulic/Lever Rear-wheel Shoe-expander In this case the cylinder bore (Fig. 28.42A) supports both inner and outer pistons. The outer piston uses a pressed-steel dust-cover welded to it and is grooved to carry a rectangular-cross-section rubber dust-seal. The inner piston uses a cup seal with a seal-spreader and a retainer-spring to preload the cup seal against the cylinder wall in the released position of the brakes. The tapered end of the cranked lever is housed in a triangular slot formed in each piston. This lever is located and pivoted on a pin in the body. During application of the foot-brake, the fluid pressure pushes the inner and outer pistons until the leading shoe is forced against the drum. Consequently, the hydraulic reaction of the fluid forces the cylinder body to slide in its slot on the back in the opposite direction, until the trailing shoe is engaged against the drum. Actually, the cylinder body and pistons float between both shoes and provide an equal shoe