Constant contact side bearing

An improved three piece side bearing for a railcar, said side bearing comprising:

• a) a cast bottom housing having a base with a flange mounting plate adapted to be attached to a bolster of a railcar truck;
• b) said bottom housing having an upwardly extending cylindrical wall section, said wall section having relatively thin walls and not being subjected to a compressive weight of the railcar;
• c) said bottom housing also having a cylindrical, center post extending from said base to a position above said plate;
• d) (a) a top cap having a wear resistant surface for engaging the bottom of a rail car,
• e) said top cap having downward depending cylindrical walls that telescope inside the extending walls of the bottom housing, said depending cylindrical walls terminating in abutment edges that engage the bottom housing to limit vertical reciprocation of the cap relative to the bottom housing;
• f) said top cap also having a center post section extending downwardly in vertical juxtaposition with said cylindrical center post of said bottom housing for also assisting in limiting vertical reciprocation of the top cap relative to the bottom housing, and for supporting the wear surface of the top cap;
• g) a continuously formed one piece, generally cylindrical elastomeric compressive spring having a top surface contacting said top cap, a bottom surface contacting said bottom housing, and a centerbore passing through said spring, said spring being formed of an elastomer having a ratio of plastic strain to elastic strain that is greater than 1.5 to 1, the molecular structure of said spring being oriented as a result of plastic deformation of said member in at least one direction, and
• h) said depending cylindrical wails of said top cap and said upwardly extending cylindrical wall section of said bottom housing being provided with at least one cooperating vertical guide for maintaining the alignment of said top cap with said bottom housing.