CHAPTER 3CHASSIS SYSTEMSChassis systems provides operators with a means ofcontrolling the direction the equipment travels andallows travel over uneven terrain by controlling theamount of shock reaching the passengers or cargo. Thischapter covers the basic principles of steering systems,suspension systems, tires, and brake systems.STEERING SYSTEMSAutomotive steering mechanisms are classified aseither manual or power. In both types, the arrangementand function of the linkage are similar. The maindifference is that manual steering requires more effortfor you to steer the vehicle. Some constructionequipment has articulated steering which is powered bythe equipment hydraulic system.STEERING MECHANISMSAll steering mechanisms have the same basic parts(fig. 3-1). The steering linkage ties the front wheelstogether and connects them to the steering gear case atFigure 3-1.—Steering linkage assembly.the lower end of the steering column which, in turn,connects the gear case to the steering wheel.The arms and rods of the steering linkage have ballends or ball-and-socket ends to provide a swivelconnection between them. These joined ends havegrease fittings, dust seals or boots, and many of themhave end-play adjustment devices. These joints anddevices must be adjusted and lubricated regularly.The arms, rods, and joints of steering linkage in yourequipment may be arranged differently from thoseshown in figure 3-1, but you will find them in the samegeneral location in the front and underneath the vehicle.The tie rod is usually behind the axle and keeps thefront wheels in proper alignment. The tie rod is dividedinto two lengths and is connected to the steering gearnear the center of the vehicle to provide for easiersteering and maximum leverage.The drag link between the steering arm and thepitman arm may be long or short, depending on theinstallation.The pitman arm is splined to the shaft extendingfrom the steering gear case. It moves in an arc with itsposition, depending on which direction the steeringwheel is turned. The arm is vertical when the frontwheels are straight ahead. Therefore, the length of thedrag link is determined by the distance between thesteering arm and the vertical position of the pitman arm.Unlike the tie rods, the length of the drag link is fixed.Part of your prestart and operator maintenanceresponsibilities is to check and service the steeringlinkage lubrication. One example is the connectingjoints between the links that contain bushings.Additionally, when a vehicle is equipped with manuallyoperated steering, check the steering gear housing forlubrication, and, if needed, add the recommendedmanufacturer’s gear lubricant. If the vehicle is equippedwith power steering, check the belt tension becauseimproper tension can cause low oil pressure and hardsteering. Check the fluid level. If the fluid level is low,add fluid to bring it up to the recommended level andonly use the recommended power steering fluid. Also,if the level is low, there may be a leak; therefore, checkhose and power steering connections for signs of leaks.3-1
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