Page 220 - Automotive Engineering Powertrain Chassis System and Vehicle Body

CH AP TER 8 .1 Types of suspension and drive

no need for any control arms and rods; and thus
only few components to handle.

From a suspension point of view:

there is a favourable wheel to spring damper ratio;
there are only two bearing points O l and O rs , which
hardly affect the springing (Fig. 8.1-31);
low weight of the unsprung masses; and
the cross-member can also function as an anti-roll bar.

From a kinematic point of view:
Fig. 8.1-31 The lateral forces F Y,W,r,o and F y , W,r,i occurring at
the centres of tyre contact during cornering are absorbed at the there is negligible toe-in and track width change on
bearing points O l and O rs . This results in a moment reciprocal and parallel springing;
M y ¼ðF Y;W;r;o þ F Y;W;r;i ÞXr ¼ F X;o b O which (depending on the
elasticity of the rubber bearing) can cause ‘lateral force there is a low change of camber under lateral forces;
oversteering’. The longer the control arms (distance r) and the there is low load-dependent body roll understeering
closer the points O l and O rs (distance b O ), the greater the of the whole axle; and
longitudinal forces F xO .
good radius-arm axis locations O l and O rs
From an installation point of view: (Fig. 8.1-31), which reduce tail-lift during braking.

the whole axle is easy to assemble and dismantle; The disadvantages are:
it needs little space;
a spring damper unit or the shock absorber and a tendency to lateral force oversteer due to control
springs are easy to fit; arm deformation;

Fig. 8.1-32 Front-mounted engine, rear-mounted drive (BMW 3 series E46, 1998). The manual transmission is flange-mounted on
the engine, which is longitudinally positioned over the front axle. The rear-axle differential is driven by means of a propshaft. The fuel
tank is situated in front of the rear axle for safety in case of an accident. The battery was placed in the boot in order to achieve
a balanced 50:50 axle-load distribution. Fig. 8.1-1 shows the rear axle in detail.

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