flange, etc. One-wear wheels are intended primarily for
if such defects are of such nature as to warrant removing
one service period.
the wheels from the axle for repairs or scrapping as
indicated. When only one wheel is found to be defective,
(2) Wrought steel wheels, untreated and heat
the wheel set (axle with pair of wheels attached) is
treated are made to AAR Specifications M107. Cast steel
removed. The pair of wheels containing the defective
wheels untreated and heat treated are made to AAR
wheel can be replaced and/or sent to a wheel and axle
Specifications M-208. Both specifications cover class (U)
shop for repairs. Common wheel defects are discussed
untreated and three classes of heat treated wheels (A, B,
and illustrated in this chapter.
and C, designating the carbon content of the steel). Class
A indicates a relatively low carbon steel wheel; class B,
4-4. Removal of Wheel and Axle Assembly
an intermediate carbon steel wheel; and class C, a
relatively high carbon steel wheel. Heat treatment of
a. Method of Wheel Removal. It is not necessary
wrought steel wheels may be by quenching the rim only or
to dismantle the truck completely to exchange a pair of
by quenching the entire wheel; heat treatment of cast
wheels. Correct procedures are listed below.
steel wheels is by quenching the rim only. The quenching
is followed by tempering.
Rim quenched wheels,
(1) Disconnect the top brake rod from the
sometimes called rim treated, are identified by stamping
truck live lever.
the letter "R" following the class letter (except that the "R"
(2) Jack the car high enough to remove the
is omitted on cast steel wheels and wrought steel wheels
for locomotives) and entirely quenched wheels by
(3) Place safety trestles under the car.
stamping the letter "E" following the class letter.
(4) Remove truck center pin and roll the truck
b. Service. The service for which the various
(5) Remove journal packing or lubricating
classes of wrought steel and cast steel wheels are
pads, journal bearing, and wedge from wheels to be
intended is described below:
(6) Pry side frames out far enough for the
untreated wheels are satisfactory.
affected wheel and axle to roll clear.
(2) Class A-high-speed service with severe
(7) Lift or roll old wheels away and replace
braking conditions and moderate wheel loads.
with new pair of wheels and roll into position.
Class B-high speed service with
(8) Replace side frame, journal bearings,
moderate braking conditions and heavier brake loads.
wedges, and center pin.
Class C-1-service with light braking
(9) Replace truck under car.
conditions and high wheel loads.
(10) Remove trestles, lower jacks, and
(5) Class C-2-Service with heavier braking
reconnect brake rod to live lever.
conditions where off-tread brakes are employed.
(11) Repack journal boxes with fresh packing
or lubricating pads and new oil.
Note. Class A wheels (lowest carbon range)
are most resistant to thermal cracking. Class C wheels
4-5. Wrought and Cast Steel Wheels
(highest carbon range) are most resistant to shelling
conditions. The different classes of wheels should not be
mixed under the same car.
(1) Wrought steel wheels and cast steel
wheels are used under freight cars as well as other
(1) One-wear wrought steel wheels are of
equipment. Both are made in a number of designs and
lighter design than the multiple-wear wheels and are for
use primarily under freight cars, though used to some
Depending upon the original rim thickness, steel wheels
extent under passenger train cars.
are classified as multiple-wear, two-wear, or one-wear
(2) Multiple-wear steel wheels are used for
wheels. Wrought steel wheels are identified by stamping
locomotives and passenger cars. They may also be used
on the back face of rim or -hub; cast steel wheels are
for freight cars.
Wheels intended for use under
identified by marking either stamped on back rim or hub
locomotives other than steam shall have mill scale
face or cast on wheel plate. Multiplewear and two-wear
removed before application to axle.
wheels, as indicated by the name, have sufficient rim
thickness to permit machining the tread and flange to new
contours after the wheels have worn to thin flange, high