Patent ID: 6895866

Claim:
A rail road freight car having: at least one rail car unit, said rail road freight car being supported by three piece rail car trucks for rolling motion along rail road tracks; at least a first rail car truck of said three piece rail car trucks having a rigid truck bolster and a pair of first and second side frame assemblies, said truck bolster having first and second ends; said first rail car truck having a suspension including first and second spring groups mounted between said first and second ends of said truck bolster and said first and second side frames respectively; said rail car truck suspension having a natural vertical bounce frequency of less than 2 Hz when said rail road freight car is unloaded; a first set of friction dampers mounted between said truck bolster and said first side frame assembly, a second set of friction dampers mounted between said truck bolster and said second side frame assembly; and said first set of friction dampers including at least a first friction dumper and a second friction damper, said first and second friction dampers being independently biased, and said second friction damper being mounted more laterally outboard than said first friction damper.