rim. Others come from wear; for example, slid-flat spots and thermal cracks from excessive braking, burst hub
from improper wheel mounting, and chipped flange from the flange striking guard-rails and frogs. For cast-
steel wheels, many defects are measured with the wheel-defect gage; the tread-worn-hollow and out-of-round
gages measure defects carrying the same names. The steel-wheel gage is used for inspecting and measuring
most defects on wrought-steel wheels.
Each time a wheel under a freight car turns, the wheel adjacent to it on the opposite rail also turns the
same amount. The reason for this is because of the solid and fixed connection between the wheels: the axle.
Axles are the object of our studies in the following section.
Section II. Axles
Railway car axles have two principal functions: they hold the wheels to track gage, and they transmit the
weight of the car and its lading from the journal bearings to the wheels. Figure 2.22 contains a drawing
showing the parts of an axle designed for friction bearings, and figure 2.23 shows the parts of an axle designed
for roller bearings. Note, in figure 2.22, the end collar designated "A"; you find this missing in the axle
diagramed in figure 2.23. Both kinds of
Figure 2.22. Axle With Friction Bearings.