and heaviest capacity axles are designated F. Because of the tremendous amount of friction generated between
the bearings and the journals, much of the wear on axles and many of the defects occur at the journals.
However, axles do bend and break, and collars and wheel seats do become worn. Thorough inspections must be
made of the axles to prevent axle failures and hotboxes. When an axle is found defective or worn to the
condemning limits, it should be removed from service and marked with the appropriate symbol.
First we talked about wheels; then we discussed axles. Now we are ready for explanations of how the
wheels are matched, mounted, and dismounted from the axle. The third and final section of this chapter is
devoted to these explanations.
Section III. Wheels on Axles
Railway wheels are pressed onto axles under high pressure. The fit must be exact for the wheel to remain
seated on the axle under the extreme stresses placed upon it in service. To insure a tight and secure fit, wheels
must be selected that fit the dimensions of the axle upon which they are to be mounted. The two wheels chosen
for a particular axle must also match each other.
During the mounting process, the journals, the wheel seats, and the wheel bores must be protected and
lubricated to prevent damage that could develop into serious trouble later when wheels and axles are placed in
service. The wheels must be exactly centered on the axle and exactly the right distance apart or they will not
roll true. Unless the mounted wheels and axles are going into service immediately, proper provision must be
made for their storage to prevent damage and protect them from the weather. Finally, since the multiple-wear
wheel may be removed, restored, and remounted, provision must be made for dismounting wheels. This section
explains each of these processes in the order mentioned.
The two principal problems involved in the business of putting the right wheels on the right axles are to
select the right size bore in the wheel for the axle it is to be mounted upon, and to match the two wheels for
type, size, and amount of wear.
a. Wheels to axles. The proper selection of the right wheel for a particular axle is complicated. But the
time and money spent