Sunday, December 9, 2012

770G and 772G Off-Highway Truck : Front Suspension (Cylinder)

Each front wheel is held by a suspension cylinder. The suspension cylinder is an oil-pneumatic hydraulic cylinder. The front suspension cylinders are the kingpins for the steering linkage. The front suspension cylinders also provide the shock absorber action between the front wheels and the machine frame.

The main components of the front suspension cylinder are a cylinder and a rod. The cylinder is fastened to the frame of the machine. As the wheel moves up or as the wheel moves down, the rod is free to move inside the cylinder. The rod moves with the wheel.

Rod Moves Up

Front suspension cylinder operation
(1) Cylinder
(2) Chamber
(3) Rod
(4) Orifices
(5) Drain ball check
(6) Cavity
(AA) Nitrogen(LL) Oil

Orifices (4) and drain ball check (5) control the flow rate of the oil from chamber (2) to cavity (6) .

When a shock load is felt in the front wheels, the front wheel will move up. This movement causes rod (3) to move up in cylinder (1). The movement of rod (3) compresses the nitrogen in chamber (2). Oil flows from chamber (2) to cavity (6) through orifices (4) and through drain ball check (5) .

The compression of the nitrogen in chamber (2) provides the shock absorber action. The suspension cylinder dampens the amount of the shock load that is felt by the machine frame.

Rod Moves Down

Front suspension cylinder operation
(1) Cylinder
(2) Chamber
(3) Rod
(4) Orifices
(5) Drain ball check
(6) Cavity
(AA) Nitrogen(LL) Oil

As the shock load diminishes, the action of the suspension cylinder is reversed. The weight of the wheel and of the front axle in addition to the pressure of the nitrogen in chamber (2) moves rod (3) out of cylinder (1). As rod (3) moves down, the oil volume of cavity (6) decreases and the oil is put under pressure. The flow of oil closes drain ball check (5). The oil pressure in cavity (6) holds drain ball check (5) closed. At this time, oil can only drain to chamber (2) through orifices (4) .

As rod (3) moves down, the lower orifice is closed and the amount of oil that goes to chamber (2) is decreased. The other orifice is slowly closed off as rod (3) moves down. This again decreases the amount of oil that goes to chamber (2). By slowly decreasing the amount of oil that drains to chamber (2), the suspension cylinder reduces the speed of downward movement for rod (3). This reduces the shock load that is created when rod (3) reaches the bottom of cylinder (1) .

MARYGAR