(10) If the frame assembly is cracked or broken,
(1) Hold the brake either vertically or horizontally
so that both frames (9) are exposed.
(11) Re-cement expander tube shields. If any
(2) Place a screwdriver against the hook of the re-
shields are loose, all shields should be removed and re-
tracting spring (1) and, with a sharp blow, disengage
cemented, reversing the block and shoe assemblies
the spring from the frame. Drive the springs through
from their original installation. Procure a good neo-
the brake and out of the assembly.
prene base adhesive compound and use per instruc-
(3) Lift the block and shoe assembly (2) from the
(4) Remove brake frame bolts (4).
(a) Clean the shields with lacquer thinner or
acetone. Do not use petroleum base solvents.
(5) Use center punch to mark upper and lower
(b) Place one shoe in the brake assembly. Re-
frames for same location on reassembly and lift upper
verse the shoe to expose a clean section of tube, free
half of frame from torque plate (8).
from initial cement. Mark the position of the extended
(6) Slide expander tube (5) and inlet connection (6)
end of the shoe on the tube. Note the position of the
from the torque plate.
mark in relation to the torque bar of the frame assem-
bly. Mark relative positions for the remaining shields.
If expander tube is stuck to the torque plate,
(c) Coat cement on the tube at each of the
work a thin piece of steel between the torque
twelve marks. Coat a spot 3 inches by 11/2 inches with
plate and expander tube and draw it around
the 11/2 inch dimension being centered over the mark.
the plate to free tube.
The 3-inch dimension should be centered between the
(7) Remove inlet connection from nozzle of ex-
pander tube, and remove packing (7) from nozzle.
d. Cleaning, Inspection, Repair, and Replacement.
(d) Coat the inside, or concave side, of the
(1) Clean the brake assembly. Use a cloth damp-
shields with cement. Keep cement confined to the cen-
ter 3 inches of the shields.
ened in acetone or lacquer thinner. Do not saturate
(e) Allow the cement to dry for 5 minutes.
(2) Inspect expander tube for signs of excessive
(f) Place a shield on the tube so that one half of
the shield protrudes from under the end of the shoe.
heat shown by brittleness, or loose fabric or rubber
around the nozzle base that might permit fluid leak-
(g) Remove the shoe assembly and press the
shield firmly to the tube.
(3) Check for loose expander tube shields. Re-ce-
(h) Install the next shoe with a shield centered
under the protruding end of the shoe. Press the shield
ment all shields as described in (11) below.
firmly to tube and install retracting spring.
(4) Inspect brake block and shoe assemblies for
(i) Continue in the same manner with the bal-
separation of lining from shoe.
ance of the shields, shoes and springs until all brake
The friction on the braking surface of the lin-
shoes and shields are in place.
ing may develop ridges and grooves. The lead-
(12) Replace expander tube if cracked or charred,
ing edge, that which is in the direction of ro-
or if the nozzle is loose.
t a t i o n , tends to wear slightly unevenly.
(13) Replace brake lining if worn beyond the mini-
Either of these conditions is normal.
mum thickness, if torque bar forms ridges on the end
face of the linings that may cause the block and shoe
(5) Inspect the frame assemblies for unusual wear
or distortion of torque bars, cracks at the welds of
assemblies to hang up, or if excessive cracking or chip-
ping is evident.
torque bars, and for cracks of elongation of frame bolt
holes. Frames should not have more than 1/16-inch
(14) Replace the frame assemblies if distorted
elongation of the bolt holes.
from any crack or damage.
( 6 ) Check for broken or distorted retracting
(15) Replace retracting springs if they are broken
springs, comparing questionable springs with new
or distorted, and when new linings are installed to re-
place worn out linings. Replace all twelve springs to in-
sure uniform retraction.
(7) Inspect inlet connection block bore, where
e. Reassembly. Refer to figure 5-7 and reassemble
packing seals, for scratches and grooves.
the brake assembly as follows:
(8) Inspect brake drums for cracks, checks, distor-
(1) Install two new packings (7) on expander tube
tion, and scored surfaces. Scored brake drums can be
nozzle (5), lubricating them with vaseline, and install
repaired by turning on a lathe. No brake lining is any
inlet connection (6).
better than the drum it contacts. The maximum a
brake drum should be turned is 0.060 to 0.080 inch.
Be sure that the inlet connection opening
(9) If any linings have come loose from the shoes,
faces the vehicle, and that the inlet connec-