Modern train locomotives are powered by several electric motors which each turn a live axle and a pair of wheels secured to the axle by a press fit. The body of the locomotive is placed on journal bearings on the portion of the axles outside of the wheels, and the electric motor is secured between the wheels. The motor, the portion of the axle between the wheels, and a set of gears are housed in an assembly which includes two motor support bearings. One motor support bearing is adjacent the inside surface of the hub of the gear on the axle, and the other support bearing is adjacent the inside surface of the hub of the wheel on the side of the axle which is opposite the axle gear. The motor support bearings are tapered roller bearings which require closely controlled axial end play to obtain optimum life while at the same time avoiding overheating and possible seizure in use. However, the best performance and longest life are obtained with minimal to slightly preloaded end play.
In known locomotive assembly processes, the wheels and bearings are press fit on the axle with a gap between two selected pieces of the assembly. The gap is measured and one or more shims are assembled into a shim pack which fits snugly in the gap, setting the end play of the bearings. However, the end play cannot be accurately set at a low tolerance using this method, and the end play increases significantly in use, resulting in relatively poor long term performance. Thus, there is a need for improved methods for setting the axial end play of motor support bearings used in locomotives, to reduce end play in assembly and in use, and improve performance and product life.
Accordingly, one object of this invention is to provide new and improved methods for setting the axial end play of tapered roller bearings.
Another object is to provide new and improved methods and apparatus for setting the axial end play of press fit tapered roller bearings.
Still another object is to provide new and improved methods for setting the axial end play of motor support bearings used in locomotives.