Page 257 - Automotive Engineering Powertrain Chassis System and Vehicle Body

Steering CHAPTER 9.1

Fig. 9.1-3 Synchronous steering A-bar on the front suspension of a left-hand drive passenger car or light van; on the right-hand
drive vehicle, the steering gear is on the other side. The steering arm (3) and the pitman arm (4) rotate in the same direction. The tie rods
(2) are fixed to these arms.

Fig. 9.1-4 Rack and pinion steering with the steering linkage ‘triangle’ behind the front axle. The spigots of the inner tie rod joints 7 are
fixed to the ends of the steering rack 8 and the outside ones to the steering arms 3 (see also Figs. 8.1-40 and 8.1-54).

pinion steering), it is most economical to fix the inner tie suspension travel, the lower joint 8 describes the same arc
rod joints 7 to the ends of the steering rack 8 (Fig. 9.1-4). 9 as the centre of the front axle housing (Figs. 9.1-6 and
8.1-37). The arc 9 must be similar to the curved path 7,

9.1.1.3 Steering system on rigid axles

Rack and pinion steering systems are not suitable for
steering the wheels on rigid front axles, as the axles move
in a longitudinal direction during wheel travel as a result
of the sliding-block guide. The resulting undesirable
relative movement between wheels and steering gear
cause unintended steering movements. Therefore, only
steering gears with a rotational movement are used.
The intermediate lever 5 sits on the steering knuckle
(Fig. 9.1-5). The intermediate rod 6 links the steering
knuckle and the pitman arm 4. When the wheels are
turned to the left, the rod is subject to tension and turns
both wheels simultaneously, whereas when they are Fig. 9.1-5 On rigid axles, apart from the two steering arms 3,
turned to the right, part 6 is subject to compression. A only the tie rod 2, the idler arm 5 and the drag link 6 are needed to
single tie rod connects the wheels via the steering arm. steer the wheels. If leaf springs are used to carry the axle, they
However, on front axles with leaf springs, the pitman must be aligned precisely in the longitudinal direction, and lie
vertical to the lever 5 when the vehicle is moving in a straight line.
arm joint 4, which sits on the steering gear 1, must be Steering arm angle l is an essential factor in the relationship
disposed in such a manner that when the axle is at full between the outer and the inner curve steering angles.

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