Page 256 - Automotive Engineering Powertrain Chassis System and Vehicle Body

CH AP TER 9 .1 Steering

Fig. 9.1-1 Damper strut front axle of a VW Polo (up to 1994) with ‘steering gear’, long tie rods and a ‘sliding clutch’ on the steering
tube; the end of the tube is stuck onto the pinion gear and fixed with a clamp. The steering arms, which consist of two half shells and point
backwards, are welded to the damper strut outer tube. An ‘additional weight’ (harmonic damper) sits on the longer right drive shaft
to damp vibrations. The anti-roll bar carries the lower control arm. To give acceptable ground clearance, the back of it was designed
to be higher than the fixing points on the control arms. The virtual pitch axis is therefore in front of the axle and the vehicle’s front end
is drawn downwards when the brakes are applied.

Slip angle, front right

Slip angle Steering wheel Steering wheel angle
angle to left

Slip angle, rear right

km h –1
0
0.5 1.0 1.5 2.0 2.5 s 3.0
Time (s)

Fig. 9.1-2 Delayed, easily manageable response of the right front wheel when the steering wheel is turned by 100 in 0.2 s, known

as step steering input. A slip angle of a f z 7 on both front tyres is generated in this test. The smaller angle a r on the rear axle, which
later increases, is also entered. Throughout the measurement period it is smaller than a f (x-axis), i.e. the model studied by Mercedes
Benz understeers and is therefore easy to handle.

258