Steering Systems

Steering Systems

Steering is the term applied to the collection of linkages, gears, and other things which all allow a vehicle to follow a desired course. The concept is similar for trucks and cars. The biggest difference between the steering system for an 18-wheeler is that it is much less responsive than a car and much more difficult.

Modern cars and trucks use rack and pinion steering mechanisms. In this type of system, the steering wheel turns the pinion gear. The pinion is responsible for moving the rack. The rack is a linear gear that meshes with the pinion, converting circular motion into linear motion along the transverse axis of the car (side to side motion). This motion applies steering torque to the kingpins of the steered wheels via tie rods and a short lever arm called the steering arm.

Rack and pinion design has the huge advantage of a large degree of feedback and direct steering "feel." In addition, it does not normally have any backlash or slack. The biggest disadvantage of this steering system is that the rack and pinion system is not adjustable. This means that when the steering system wears out and develop lash, the only way to fix it is completely replacing the system.

Older steering systems use the recirculating ball mechanism. This system is still found on trucks and utility vehicles. It is a variation of the even older worm and sector design. The steering column turns a large screw, or the "worm gear" which meshes with a sector of a gear. This causes it to rotate about its axis as the worm gear is turned. An arm is attached to the axis of the sector which moves the pitman arm. The pitman arm is connected to the steering linkage and steers the wheels.

The recirculating ball version of the apparatus reduces the considerable friction by placing large ball bearings between the teeth of the worm and those of the screw. The balls exit from between the two pieces into a channel internal to the box which connects them with the other end of the apparatus and so they are recirculated.

The recirculating ball mechanism has the distinct advantage of a much greater mechanical advantage. This made it present on larger, heavier vehicles. With the universal adoption of power steering, however, this is no longer as important. The recirculating ball design has a perceptible lash or "dead spot" on center. This means that when the wheel is centered, a minute turn of the steering wheel in either direction does not move the steering apparatus.

For more information on the hazards of truck systems, please visit http://www.truckaccident-lawyers.com

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