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The summary of Chassis andSuspension design

Chapter 1 History of chassis:The purpose of a motor car chassis is to connect all four wheels with a

structure which is rigid in bending and torsion (will not sag or twist). It

must be capable of supporting all components and occupants and should

absorb all loads fed into it without deecting unduly.

chassis is only a mean to an end.

In descending order of magnitude the ma!or loads in"ol"ed are#

$) %ear suspension and &nal dri"e') ront suspension and steering) *ngine and gearbo+,) uel tan-) Seats and occupants /steering column /pedals and other controls0) %adiator1) 2attery3) Spare wheel

Chapter2 The main types of chassis:The space frame is the most e4cient type of chassis which it is possible to

build in limited production. The best e+ample of space frame chassis fromthe point of "iew of rigidity would be a s5uare section rectangular bo+/

with ends/ sides/ top and bottom triangulated by diagonals running from

one corner through centre to the opposite corner .this would be the

lightest/ sti6est/ simplest and cheapest type of chassis/ but at the same

time it would be entirely impractical for automoti"e applications.

7articularly from the point of "iew of accessibility.

In the course of design. *ach panel or bay of unitary construction chassis

must be stabilised to carry out the function of transferring loads. The

simplest way to achie"e this would be to use a large round section tube

with the ends blan-ed o6

8owe"er the best design is the one which departs least from the ideal and

as round section chassis body cannot be considered practical the best

compromise would seem to be a s5uare section layout with large radius

corners

ny operation on a tube such as tapering it or cutting holes in it/ must

ha"e ad"erse e6ects on it structurally. 9ith e+ing holes crossing load

paths change their shape since there must be holes despite the reduction

on frames and bul-heads to stabilise the surrounding areas

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The load capacity of a unitary construction chassis in bending should be

e+tremely good because bending loads are resol"ed into pure tension and

compression in the undertray and roof/ to which type of loads these areas

are ideally suited. Such a chassis should also be "ery good from the

torsional point of "iew but in practise e"erything depends on the torsional

point of "iew. This is particularly true in the case of and open car which

lac-s the diagonal bracing the diagonal bracing pro"ided in a closed car

by the roof. *"en here/ howe"er with careful design ade5uate torsional

sti6ness should be a"ailable. 9eight should be lower than for any

e5ui"alent chassis because with good design a far greater proportion of

the weight of the material can be made to carry loads than is the case

with a separate chassis and body

In general/ a unitary construction design should be sti6er than an

e5ui"alent tubular space frame and body for the same weight/ or lighter

for similar sti6ness. ccessibility depends on the design and this in turndepends on the design and this in turn depends on the degree of

compromise reached between chassis sti6ness and practicability.

:urability depends on operating conditions but should be god/ all other

things being e5ual while accident damage should be localised ; gi"en

good design< ma-ing the cost of repairs fairly low.

Chapter 3 Material::espite the recent trend towards monoco5ues/ there still seems to be a

considerable future for tubular steel chassis. or such a purposes a wide

"ariety of alloy steel tubing is a"ailable/ ranging from high 5uality chromemolybdenum and nic-el chrome steel to the ordinary mild steel used by

the ma!ority of specialist sports and racing car constructors.