Retarder control valve assembly and system for rail cars

A pilot controlled springless retarder control valve, comprising:

• a hollow cartridge body having a sidewall bounding a bore having a first end and an opposite open second end, the sidewall including at least one side opening connected to the bore between the first end and the open second end and a valve seat disposed about the open second end;
• the first end of the bore having different diameters and containing a differential pilot piston member having pistons of different diameters, the differential piston member being movable within the bore responsive to pressurized air pilot signals, a spool connected to the differential piston member for movement therewith and extending through the bore to the open end, and a poppet connected to the spool and movable therewith relative to the valve seat between a closed position in sealed relation therewith wherein pressurized air will be prevented from flowing past the valve seat, and a fully open position spaced from the valve seat to allow flow of the pressurized air therebetween and through an air flow path of the bore bounded generally by the differential piston member and the poppet;
• and
• the differential piston member, the spool, and the poppet being configured so as to be movable solely by the pressurized air pilot signals when present.