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Suspension Systems
Shock Absorbers

Equipment Operator Basic - Beginning construction equipment operators manual
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l l l l l Hard or rough ride Sway on turns Spring  breakage Sagging springs Noises The components of a suspension system are the springs  and  shock  absorbers.  Some  suspension  systems also have torsion bars. SPRINGS The springs support the frame and the body of the vehicle as well as the load the vehicle carries. They allow the wheels to withstand the shocks of uneven road surfaces and provide a flexible connection between the wheels and the body. The best spring absorbs road shock rapidly  and  returns  to  its  normal  position  slowly. Extremely  flexible  or  soft  springs  allow  too  much movement of the vehicle superstructure, while stiff, hard springs do not allow enough movement. The springs do not support the weight of the wheels, rims,  tires,  and  axles.  These  parts  make  up  the “unsprung  weight”  of  the  vehicle.  The  unsprung  weight decreases the action of the springs and is, therefore, kept to a minimum to permit the springs to support the vehicle frame and load. Multiple  Leaf  Springs The multiple leaf spring is part of the front axle suspension system, as shown in figure 3-5. It consists of a  number  of  steel  strips  or  leaves  of  different  lengths fastened together by a bolt through the center. Each end of the largest or master leaf is rolled into an eye which serves as a means of attaching the spring to the spring hanger and spring shackle. Leaf rebound clips surround the leaves at two or more intervals along the spring to keep them from separating on the rebound after the spring  has  been  depressed.  The  clips  allow  the  spring leaves  to  slide  but  prevent  them  from  separating  and throwing the entire rebound stress on the master leaf. The spring thus acts as a flexible beam. Leaf springs may  be  suspended  lengthwise  (parallel  to  the  frame)  or crosswise. When a leaf spring is compressed, it must straighten out or break; therefore, spring shackles are required at one or both ends of the spring. Spring shackles provide a swinging support and allow the spring to straighten out when compressed. One shackle is used in either the front or rear support of springs installed lengthwise. Two shackles  support  springs  installed  crosswise.  Figure  3-6 shows how a leaf spring is attached to a frame by a spring  shackle. The most common types of spring shackles are the link shackle and the U-shackle. Heavy vehicles have link shackles. The U-type is more common on passenger cars and light trucks. On some wheeled tractors, link shackles support a transverse  spring  on  the  dead  front  axle.  Most  wheeled tractors  do  not  even  have  springs,  and  all  load cushioning  is  through  large,  low-pressure  tires. Track tractors have one large leaf spring (fig. 3-7) supported without spring shackles. Fastened to the engine support, it rests on the frame supporting the tracks and rollers. Brackets on the track frames keep the spring  from  shifting. Figure 3-6.-Cross section of a shackle link. Figure 3-7.-Partially removed tracklayer spring. 3-5







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