TM 9-2330-392-14&P
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Change 2
1-11
EQUIPMENT DATA - Continued.
Section III. TECHNICAL PRINCIPLES OF OPERATION
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HYDRAULIC BRAKE SYSTEM.
a.
The hydraulic brake system applies the brakes automatically when the towing vehicle slows or stops, or when
the trailer breaks away from the towing vehicle.
b.
The hydraulic brake system consists of a hydraulic brake actuator assembly, hydraulic brake tube assemblies,
hose assembly, and wheel cylinders to activate the service brakes.
c.
The major components of the hydraulic brake system and their function are as follows:
(1)
Lunette Ring. Attaches to towing vehicle pintle hook. The lunette ring controls the master cylinder
assembly When the towing vehicle goes forward, the lunette ring is pulled and the brakes are
released. When the towing vehicle slows down, the weight of the trailer pushes the lunette ring into
the towing vehicle and the brakes are applied.
(2)
Master Cylinder Assembly. Changes mechanical motion of lunette ring and breakaway lever into
hydraulic pressure. It has a built-in shock absorber to prevent jerky lunette ring movement. The
damper also slows the rate of hydraulic pressure increase when the towing vehicle backs up, thus
allowing the trailer to be slowly backed up for short distances on level terrain.
(3)
Breakaway Chain. Attaches to towing vehicle. It will pull the breakaway lever up if the trailer and
towing vehicle uncouple.
(4)
Breakaway Lever. Controls the master cylinder. When the lever is up, the brakes are applied. When
it is down, the lunette ring controls the master cylinder.
(5)
Leaf Spring. Holds the breakaway lever up. The breakaway lever must be reset any time it has been
pulled up.
(6)
Hydraulic Brake Tubes and Hoses. Transfer hydraulic pressure from the master cylinder assembly to
the wheel cylinder.
(7)
Wheel Cylinder. Changes hydraulic pressure into mechanical motion. When the wheel cylinder is
pressurized, it pushes the brake shoes against the brake drum.
(8)
Brake Shoes. Are pushed against the brake drum by the wheel cylinder.
Suspension:
Shock Absorbers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydraulic, double-acting
Tires:
Quantity: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37X12.50R16.5 LT
Ply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-ply tread, 2-ply sidewall
Inflation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 psi ± 2 psi (117 kPa ± 13.8 kPa)
Towing Attachment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lunette Ring
Wheels:
Rim Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5 X 8.25 X 6.5 BC
Number of Lugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Brakedrum:
Maximum inside diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12.09 in. (30.7 cm)
