Brake Assembly - TM-10-3930-634-340186

TM 10-3930-634-34

(10) If the frame assembly is cracked or broken,

(1) Hold the brake either vertically or horizontally

replace it.

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

frame.

tions.

(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-

NOTE

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-

frames.

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.

components.

(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.

age.

(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.

NOTE

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-

ones.

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.

CAUTION

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-

re-rivet them.

5-14