lllllHard or rough rideSway on turnsSpring breakageSagging springsNoisesThe components of a suspension system are thesprings and shock absorbers. Some suspension systemsalso have torsion bars.SPRINGSThe springs support the frame and the body of thevehicle as well as the load the vehicle carries. Theyallow the wheels to withstand the shocks of uneven roadsurfaces and provide a flexible connection between thewheels and the body. The best spring absorbs road shockrapidly and returns to its normal position slowly.Extremely flexible or soft springs allow too muchmovement 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 weightdecreases the action of the springs and is, therefore, keptto a minimum to permit the springs to support thevehicle frame and load.Multiple Leaf SpringsThe multiple leaf spring is part of the front axlesuspension system, as shown in figure 3-5. It consists ofa number of steel strips or leaves of different lengthsfastened together by a bolt through the center. Each endof the largest or master leaf is rolled into an eye whichserves as a means of attaching the spring to the springhanger and spring shackle. Leaf rebound clips surroundthe leaves at two or more intervals along the spring tokeep them from separating on the rebound after thespring has been depressed. The clips allow the springleaves to slide but prevent them from separating andthrowing the entire rebound stress on the master leaf.The spring thus acts as a flexible beam. Leaf springsmay be suspended lengthwise (parallel to the frame) orcrosswise.When a leaf spring is compressed, it must straightenout or break; therefore, spring shackles are required atone or both ends of the spring. Spring shackles providea swinging support and allow the spring to straighten outwhen compressed. One shackle is used in either the frontor rear support of springs installed lengthwise. Twoshackles support springs installed crosswise. Figure 3-6shows how a leaf spring is attached to a frame by aspring shackle.The most common types of spring shackles are thelink shackle and the U-shackle. Heavy vehicles havelink shackles. The U-type is more common on passengercars and light trucks.On some wheeled tractors, link shackles support atransverse spring on the dead front axle. Most wheeledtractors do not even have springs, and all loadcushioning is through large, low-pressure tires.Track tractors have one large leaf spring (fig. 3-7)supported without spring shackles. Fastened to theengine support, it rests on the frame supporting thetracks and rollers. Brackets on the track frames keep thespring from shifting.Figure 3-6.-Cross section of a shackle link.Figure 3-7.-Partially removed tracklayer spring.3-5
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