Abstract: An empty or loaded railroad brake control device includes a valve adapted to communicate a brake cylinder pressure chamber with a supplemental volume reservoir when the railroad car is not fully loaded. The valve is held in the closed position by a spring, but when a car is less than fully loaded, a load sensing device determines the relative position of the sprung and unsprung portions of the vehicle and transmits this information to the valve which opens to communicate the supplemental volume reservoir with the brake cylinder pressure chamber. The valve includes a pressure release valve, adapted to release the pressure from the supplemental volume reservoir when the brakes are released. An overpressure valve permits partial build-up of the pressure in the brake cylinder before the supplemental volume reservoir is connected.

Abstract: A power cylinder unit, adapted for use in truck mounted, self-aligning railway freight car tread brakes comprises a housing, a bulkhead which seals the housing, and a rigid, but moveable piston rod. The housing includes an annular bearing adapted to provide lateral support for piston rod and a spring which urges the piston toward the bulkhead. The combination of the housing, the bulkhead and the piston head define a gas-tight space to which the brake operating compressed air is passed. The piston head includes three circumferential grooves adapted to receive a bearing ring, a fluid sealing ring and a lubricating ring. The cylinder may be eccentrically mounted.