permit quick tightening. Use a suitable spanner wrench for prompt tightening of nut before the pinion
gear cools. After it has cooled, remove dummy pinion nut and check pinion gear carefully by
measurement for proper advance. If the mounting is satisfactory, apply and tighten the regular
lockwasher and nut.
When a wheel set is removed from a truck for any reason, the gears should be thoroughly
inspected. The condemning limits for axle and pinion gears are given in the inspecting procedure as
follows.
(1) Inspect visually or magnetically for broken, chipped, or pitted teeth. Pinion and axle
gears should be condemned when more than 20 percent of total working surface of teeth are chipped or
pitted. Axle gears should be discarded when either one of the working surfaces is worn to a point where
a step 1/32-inch deep exists in the root of the gear tooth where contact with the pinion ends.
(2) Check for wear limits determined by dimension across tip of tooth. The minimum
allowable dimension at this point is 3/32 inch for axle gears and 1/32 inch for pinions.
(3) Light scuffing is characterized by vertical, root-to-tip lines and is an indication of faulty
lubrication which, if not corrected, may result in ultimate destruction of the teeth. The heat generated as
a result of this condition may cause damage to the armature bearings.
When gears with a hump at the pitch line or steps at root of tooth are disturbed by
application of new axle linings or mated with other gearing, they will operate with interference stresses
and torsional vibration until battered in a new mating fit. Operation under this abnormal condition may
lead to fatigue failure of gear teeth and shorten the life of armature windings.
2.20. CABLES AND WIRING
Cables and wiring must be inspected whenever an opportunity presents itself. This includes
insulated bus bars as well as wires and it applies, of course, only to exposed sections. Condition of the
wires is determined by megger and high potential tests. Cleaning should be done by wiping with rags or
using a suitable solvent; if a solvent is used, all traces must be removed. When the cleaning is
completed, paint accessible sections, particularly those exposed to dirt, with an insulating paint. If any
section of wiring is found to have deteriorated excessively because of heat, consider relocating
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