j. Chipped flange (Rule 78--AAR symbol 78). A wheel is condemnable if a piece is chipped from the
flange 1 1/2 inches or more in length and 1/2 inch or more in width. This defect is caused by the
flange striking guardrails and frogs. If the chipped area is
large, the likelihood of equipment derailment is great. A
condemned wheel with the chipped-flange defect is shown
in figure 2.10.
k. Cracked or broken plates or brackets (Rule 78--
AAR symbol 78-B). Any wheel with a cracked or broken
plate is condemnable because this defect is quite likely to
cause the wheel to fail or collapse. Almost invariably,
wheel plates crack from the inside out. Not all causes of
this defect are known, but thin and hard plates resulting
from improper manufacturing processes are a chief cause.
Also, when excessive braking is necessary, such as might
Figure 2.10. Chipped-Flange Defect.
be needed on mountain runs, the wheels are subjected to excessive stresses and heating. A picture of a wheel
with a cracked plate is shown in figure 2.11.
l. Broken rim (Rule 78--AAR symbol 78-R).
Minor chipping on the outside edge of the rim does not
impair the serviceability of wheels; there are limits,
however, that cannot be exceeded. Figure 2.12 shows
the methods of gaging the two types of broken rims. If
the rim is broken and the slope of the break is inward,
the condemning limit is 3 3/4 inches from the flange
measured across the tread. If the break is vertical or
sloping outward, the condemning limit is 3 1/2 inches
Figure 2.11. Cracked Plate.
measured in the same way.
2.10. DEFECT AND WEAR LIMIT--WROUGHT-STEEL WHEELS
The materials specifications and the details of defect and wear limit for wrought-steel wheels, like cast-
steel wheels, are