SPRING 7N1228 - Caterpillar

Introduction
For Specifications with illustrations, make reference to the Specifications For 789 Truck, Suspension Cylinders, Form No. SENR3435. If the Specifications in Form SENR3435 are not the same as in the Systems Operation and the Testing And Adjusting, look at the printing date on the back cover of each book. Use the Specifications given in the book with the latest date.Front Suspension Cylinders
Each front wheel is held by a suspension cylinder, which is an oil-pneumatic hydraulic cylinder. These cylinders are the kingpins for the steering linkage. The cylinders also give the machine a smooth operation (ride) by control of the shock the front wheels get during operation.
Front Suspension Cylinder Operation (Rod Moves Up)
(1) Housing (2) Nitrogen chamber (3) Rod (4) Orifices (two) (5) Ball check (6) Cavity (7) Cavity (8) Oil chamberHousing (1) is fastened to the frame of the machine. Rod (3) is free to move up and down inside of the housing, as the wheel moves up and down.The control of the shock felt by the front wheels is done by the controlled rate of oil flow, through orifices (4) and ball check (5), from oil chamber (8) to cavities (6) and (7). When a shock is felt, the wheel is moved up which causes the rod to move up in the housing. The movement of the rod puts the nitrogen, in nitrogen chamber (2), in compression. The compression of the nitrogen moves the oil from chamber (8) to cavities (6) and (7) through the orifices and the ball check.
Front Suspension Cylinder Operation (Rod Moves Down)
(1) Housing (2) Nitrogen chamber (3) Rod (4) Orifices (two) (5) Ball check (6) Cavity (7) Cavity (8) Oil chamber.As the shock goes away, the action of the suspension cylinder goes in reverse. The weight of the wheel and axle plus the pressure of the nitrogen in chamber (2) moves the rod out of the housing. As the rod moves down, the oil volume of cavities (6) and (7) decreases and the oil is put under pressure. The pressure oil closes ball check (5). The oil must flow out through orifices (4) to chamber (8).As the rod moves down, the lower orifice is closed and the amount of oil that goes to chamber (8) is decreased. The other orifice is slowly closed off as the rod moves down, which again decreases the amount of oil that goes to chamber (8). The orifice slowly being closed prevents the rod from hitting the bottom of the housing with a shock.Rear Suspension Cylinders
Two oil-pneumatic hydraulic cylinders are fastened between supports on the rear of the vehicle frame and brackets on the lower part of the differential housing. The location of each suspension cylinder is directly behind and in line with each side rail of the frame. A support, which is fastened to the front side of the differential housing, is connected to the frame by a ball joint. The two suspension cylinders give the "spring action" between the rear wheels and the vehicle frame. They