Crane - TM-5-5420-279-230032

TM 5-5420-279-23

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Crane

The crane is hydraulically powered and controlled and installed on the vehicle, the use of a

knuckle boom system enables the boom of the crane to be folded hydraulically within the limited

mounting space for transit. When folded, the crane occupies an area approximately 7 ft 10 in

(2.4 m) high by 4 ft 3 in (1.3 m) at the front end of the launcher vehicle.

The crane usage is restricted to bridge deployment or retrieval activities.

The crane base is a welded fabrication and incorporates a stabilizer beam and a pivot

beam for three-point crane support. The supporting framework extends rearwards from the crane

itself along the length of the vehicle and attaches to the vehicle chassis at four positions to

distribute the weight of the crane and any load suspended from it during operation.

Incorporated into each side of the crane base is a stabilizer leg, deployed and operated by

stabilizer hydraulic cylinders, which is attached to a load-spreading pad at a knuckle joint and

lowered to the ground to level and support the crane and the forward end of the vehicle. Lock

valves are flanged to the hydraulic cylinders to prevent cylinder retraction in the event of hose or

hydraulic system failure. The crane cannot be operated unless both its stabilizer legs are

deployed and down. A level is provided for each stabilizer leg and, with both stabilizer legs

grounded, horizontal setting is achieved by adjustment of one stabilizer leg only.

The crane column is supported and rotates on a low-friction ball bearing rotate ring, which

is protected by lip seals from dirt and foreign body ingress. The rotate system is driven from a

hydraulic piston motor with a hydraulically-operated, spring-loaded, multi-disc brake via a

planetary gear reduction.

The knuckle boom system consists of a main boom and a three-part telescopic jib.

Mounted on the jib is a rotatable load hook with a safety catch. The boom and jib are welded

fabrications and the jib is of hexagonal section. The telescopic sections of the extendible jib slide

on wear resistant guide pads. The boom and jib are actuated by the lift, the jib and the three

telescopic extension hydraulic cylinders.

The crane hydraulic system is comprised of the hydraulic lift cylinder, jib hydraulic cylinder,

rotate motor, three jib-extension hydraulic cylinders and two stabilizer-leg hydraulic cylinders.

Hydraulic power is supplied to the crane hydraulic system from the transmission-driven

pump and controlled by an operator seated at the main control valve bank at the side of the crane

column. The operator seat is stowed for transportation and released to the operating position by

shoot bolt. A ladder, with non-slip rungs and extending above the operator seat, provides safe

access to the control station and seat.

The main control valve bank is a four-`slice' selector valve and a load-sensing system is

incorporated. A further control valve, for the operation of each stabilizer leg, is fitted at each side

of the crane base. All controls are spring loaded to return to the `off' position when released.

Multi-function, pilot-valve-controlled load, hold valves are fitted to every hydraulic cylinder

as protection against hose rupture, system overload, cavitation, overspeed under load and

uncontrolled movement in the direction of load movement.

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