Body Side Bearing A steel plate or wedge, fastened to the car body at each side bearing location to act as the interfacing member with the truck side bearing. In North America the body side bearing characteristics are specified by AAR Standard S-235.
Bolster Pockets (or Wedge Pockets) Cavities in the sides of the truck bolster, designed to contain the friction snubbing system wedges. They provide the mating inclined surfaces for the sloped sides of the friction wedges to bias the vertical faces of the wedges against the column wear plates in reaction to the force of the wedge springs. This creates the normal force against the column wear plates providing the desired friction force that limits bolster vertical motion.
Cage The metal housing, fastened directly to the truck bolster, that contains the side bearing components.
Column Pressure The normal force exerted by the friction wedges against the side frame columns. This force, multiplied by the coefficient of friction between the wedge face and column wear plate, is the snubbing force (friction force) that limits bolster vertical motion for damping undesirable dynamics.
Constant Damping Truck Trucks having a friction snubbing system such that the force of the springs biasing the friction wedges against the side frame columns remains unchanged as the bolster moves vertically. Ride Control™ trucks are the more common example of constant damped trucks.
Control Point Gage Gage used on Ride Control™ trucks for measuring the space between the pocket slopes across the bolster end, referencing the casting work points, or control points, that define the location of the sloped surfaces.
End Closure A specially shaped steel plate, used to “close” the normally open ended Stucki cages for proper containment of the resilient elements.
Extended (Long) Travel Side Bearing A side bearing which is designed to vertically compress 5/8” from setup height to solid height.
Friction Wedge (or Shoe) A wedge shaped metal, or urethane backed metal element that fits into truck bolster pockets (or sometimes in the side frames of certain truck designs). The wedges are biased to the columns by compression springs, providing an energy dissipating friction force that impedes bolster vertical motion and a normal force that acts to hold the side frames square to the bolster.
Hockey Stick Term applied to a specially designed “pry bar” or lever to depress Ride Control™ friction wedges sufficiently to allow the insertion of pins through the sides of the pockets and wedges.
ISB Resilient truck side bearings that incorporate a free rolling roller, providing the high hunting control of resilient side bearings and low curving resistance of roller side bearings.
Pre-Load The compressive force or load borne by a resilient, constant contact side bearing at a defined compressed height, usually 5 1/16" for standard designs.
Resilient Side Bearing (RSB) A constant contact type side bearing that utilizes some form of a resilient element to maintain a compression force and proportional shear restraint between the truck and car body, the purpose is to control truck hunting.
RFE Acronym for “Resilient Friction Element,” a friction wedge developed and patented by A. Stucki Company that incorporates a resilient pad on the sloped surface of the friction wedge.
Set Up Height The specified vertical dimension measured from the truck bolster to the body side bearing that a constant contact side bearing is compressed to, under the weight of the car body, to yield the design pre-load for optimum performance.
Slope Wear Plate Steel plate applied to inclined surface of the bolster wedge pocket, acting as replaceable wearing liners to protect the bolster pocket from wear. Hardened steel or stainless steel when used with all metal friction wedges, but mild steel can be used for Stucki RFE’s.
Standard Travel Side Bearing A side bearing which is designed to vertically compress 1/4” from setup height to solid height.
Threshold Speed The speed at which wheelset lateral oscillations become consistent, and of sufficient magnitude to intiate truck hunting.
Truck Hunting A dynamic lateral instability of wheelsets that occurs particularly under conditions of light vertical loading and high speed during which wheelsets oscillate laterally with respect to the rails. Hunting causes severe truck component wear, structural and lading damage and derailments.
Variably Damped Truck Trucks having a friction snubbing system such that the force of the springs biasing the friction wedges against the side frame columns increases as the bolster is depressed vertically. Barber™ trucks are the more common examples of variably damped trucks.
Wedge Height The vertical location of a specified point of a friction wedge referenced usually to the top of the bolster. It is a measure of the effectiveness of the snubbing system, the higher the wedge, the lower the effectiveness.
Wedge Rise The increase of wedge height measured from the new nominal condition that occurs as a result of wear of the mating metal faces of the column snubbing system.
Witness Groove Wear limit indicators cast into the friction wedges at corners of the vertical or wearing face that define the maximum allowable wear of the friction face.
© 2007 A. Stucki Company. All Rights Reserved.