LightAuto

Past Diversity in Design

Part One, Chassis diversity.

Today's Mini and Supermini cars have a basically similar specification. A water-cooled, overhead camshaft, four cylinder, engine transversely mounted, driving the front wheels. Coil springs all round, Mcpherson struts at the front and independent or torsion beams at the rear. All attached to a unitary chassis.
It has only been this way for the last twenty years. For the half century before that there was a great diversity in the design of small cars. It is that diversity that will be revealed to you in this article, using the details of the one hundred and fourteen small cars with engines up to 1200cc, from fourteen countries that where produced during the period 1945 to 1989.
They are grouped in the period in which they where first produced to indicate the trends in in design at that time. A great number of the designs where produced for a long period, so the earlier trends in design where mixed with those from a later period, but in time the earlier designs faded away
 
 
Number of models Produced




Date First sold after 1945 Pre-war models 1945   to 1959 1960 to  1969 1970 to 1979 1980 to 1989
By Country




Austria 0 1 1 0 0
Czechoslovakia 1 1 1 0 0
DDR 1 2 0 0 0
France 1 6 8 5 4
Germany (west) 0 10 3 2 1
Italy 3 5 5 4 4
Japan 0 2 12 4 7
Netherlands 0 1 1 0 0
Spain 0 0 0 1 2
Sweden 0 2 0 0 0
United Kingdom 9 11 4 4 1
USA 0 1 0 0 0
Yugoslavia 0 0 0 1 1
Europe wide 0 0 0 1 3
Total 14 42 34 22 23

The chassis layout used has shown the most dramatic change in that period, as the chart below shows. Moving from universal use of the front engine/rear wheel drive to the use of all three layouts for over thirty years, to the almost universal use of the front engine and front wheel drive layout.
  Figure 1 Chassis Layout
The chassis types utilized have gone from a diverse selection to the universal use of the unitary type as the chart below shows.
The ladder frame had been used almost since the beginning of the motorcar and didn't finally fall out of use until the 1970's. The platform and backbone types of chassis were used for a period of about forty  years before the unitary chassis that had first been in use before the Second World War became the universal choice.
  Figure  2 Chassis Type
Suspension systems have also gone through great changes. Beam axles and leaf springs were used by the majority of manufacturers up to the middle of the nineteen thirties. The cars that were produced after the war reflected the design changes that were introduced in the second half of that decade. The beam axle was already falling out of use for the front suspension. Independent designs were soon to become universal.
Figure  3 Front Suspension Types
The springs used with beam axle front suspension designs were still leaf springs, it was only how they were mounted that showed any diversity. Independent systems on the other hand lent themselves to a wider variety of springing mediums. Leaf springs were again used, but other types of spring were used, torsion bars, rubber in the Mini, hydraulic and rubber was used by BMC, also hydraulic and gas systems were used by both BMC and Citroen before the the coil spring became dominant.
  Figure  4 Front Suspension Springs Used
                                                                                                                 Read in conjunction with figure 3
The beam axle remained in use for rear suspension systems right to the end of the period studied. At first it was live axles used to drive the rear wheels in the the designs with the front/rear layout, but the later use of beam axles were dead (undriven) axles used on front wheel drive cars.
I have divided the independent rear suspension systems into swing axle and others so that I can show the period of use of the swing axle type of drive and suspension system. Swing axles were used in rear wheel drive cars. The increasing adoption of the front wheel drive system gave designers the option to use an independent type of rear suspension without excessive cost as an alternative to the beam axle or the torsion beam. The latter is a hybrid of the other two systems.
  Figure  5 Rear Suspension Types
As beam axles were used at the rear for a longer period of time, a greater diversity of springing medium was in use. The simple double half elliptic spring layout had remained in use throughout most of the period, making a comeback in the last decade. The use of the transverse leaf spring fell out of use in a similar period as that at the front. Torsion bar springs had limited use and the coil spring were increasingly used.
Figure  6 Rear Beam Axle Suspension SpringTypes
                                                                                                                Read in conjunction with figure 5
Although swing axles were only used at the beginning of the study period, a variety of spring types were used. Transverse leaf springs were the pre war choice but torsion bars and coil springs were used in the next decade and the only car with swing axles introduced in the nineteen sixties used coil springs.
  Figure  7 Rear Swing Axle Suspension SpringTypes
                                                                                                                Read in conjunction with figure 5

The other forms of independent rear suspension used a variety of spring types throughout the study period, as diverse at the end as at the beginning. The torsion bar retaining its place throughout and only the coil spring proving more popular.
Figure  8 Rear Independent Suspension SpringTypes . Read in conjunction with figure 5

Up to the nineteen sixties drum brakes were the only type available for economy cars and disc brakes only became available for expensive cars a short time before. Some of the cars produced after the war had mechanical cable operated brakes, though the  use of hydraulic operation soon became universal. The use of all drum brake systems persisted throughout the time period of the study, but the disc front and drum rear layout rapidly became the popular layout when disc brakes became available. A small number of cars were fitted with disc brakes front and rear during the sixties and seventies, but being expensive and not strictly necessary in a light car the layout was not used in the eighties.

  Figure  9 Brake Types
Motoring For the Masses Part Five 1953.
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