f. High flange (Rule 76--AAR symbol 76). When the height of the flange is 1 1/2 inches or more above
the center of the tread, the wheel has a high flange and must be turned on a lathe until the tread and flange are
restored to original contour. Figure 2.4 shows how to measure for the high flange with the standard steel-wheel
gage. When the tip of the flange touches the horizontal part of the gage, applied as shown, the wheel is
g. Thin rim (Rule 79--AAR symbol 79). Wheels that have rims worn down to 3/4 inch should be removed
from freight service, and wheels with rims as thin as 1 inch should be removed from passenger service. If any
wheel is turned to remove any other defect and the limits above are reached in the process, the wheel should be
removed from service; however, if the 1-inch limit for passenger service is reached, the wheel can be restored to
original tread and flange contour and used in freight service until the condemning limit of 3/4-inch rim
thickness is reached.
h. Cracked plates (Rule 80--AAR symbol 80-A). Radial cracks in wheel plates almost always originate in
either the hub or the rim and should be reported and marked either cracked-hub or cracked-
rim. Either defect condemns the wheel from service.
Circumferential cracks can be detected easily with
careful inspection of wheels. If neglected, a 2-or 3-inch
crack will grow into the "cupid's bow" crack shown in
figure 2.18. The name is derived from the bow shape
the crack takes when the two ends turn outward toward
the rim. If neglected still longer, the crack will extend
through the rim, as shown in figure 2.19, and the wheel
will fail. Therefore, any wheel with a crack in its plate
should be removed from service.
i. Built-up tread (AAR symbol 107). Figure 2.20
shows a wheel with a built-up tread.
This defect is
caused in one of two ways: part of the tread metal is
dragged over other parts of the tread; or metal from a
Figure 2.18. Circumferential Cupid's Bow
brake shoe is deposited on the tread while the brakeshoe
metal is in a plastic state resulting