In developing a new model for mass production, the body en gineer must co-operate with the engineers of the mechanism, so that all parts are arranged to suit everyone concerned and yet leave attractive body lines. The general layout, including all parts of the car, was roughly made. The seats were located and head room vision, among other things, fixed. Then the designer sketched the outline of the body to agree with the prevalent style trend. All curves were laid out full size as accurately as possible.
A full-size model was then built of soft wood. In it were located the seats, steering wheel, height from ground, and so on, and this model, when photographed, was similar to the car to be pro duced. The wooden model was then inspected and lines corrected until the whole appearance was in harmony. Sometimes a coloured quarter-size model was made of clay or gypsum. This, however, did not give the same impression as the full sized body, because of the different angles of vision in the two cases. These small models would show lines which could not be seen in a full size model and when reproduced in full size the result was frequently disappointing. After the model was approved, the parts of the body were detailed and these details went to the die designer who designed the dies used to press all parts from steel sheets.
These parts were then welded together, mostly by "spot weld ing," which involves simply the forcing of electric current of high amperage and low voltage through a small area, thus fusing the two sheets together. Other methods of welding were also used de pending upon the conditions. Among them was the process of "electric butt welding." By this means steel sheets are welded edge to edge. The process required special machines shaped to conform to the pressed parts. As much as 1so inches have been welded in a fraction of a second. Two other welding processes in extensive use were "oxyacetylene welding" and "electric arc weld ing." The early steel bodies had baked on them an enamel of excellent wearing quality, but only black colour could be used on account of the high baking temperature F.) ; later coloured enamels were produced but the baking temperature had to be considerably reduced. In 1939, however, cellulose lacquers were introduced which were available in many colours. The trend in car design in 1940 was towards the "Streamline" or "Teardrop." The theo retical lines, however, had to be altered somewhat because of necessity and also to adhere to style. The streamlining of bodies added considerably to speed for the same horse-power.
During the few years preceding 1940, another addition to the duties of the body engineer was made. Previous to that time auto mobiles, in general, had a chassis frame on which all mechanical parts, including springs and wheels, were securely placed; the body was bolted to this chassis. At that time, however, the tend
ency was to abandon the chassis frame proper and build the body strong enough to make any other support superfluous. This meth od was adopted very rapidly and it was expected that all chassis would shortly be obsolete, to a large extent because of weight saving.
Experience in all-steel body construction has proved that a re duction of the number of pieces used in the body reduces costs; because fewer pieces have to be handled in the plant and fewer kept available, so that production will not be held up on account of one or more missing details.
The larger stampings, involving large steel sheets, with all formations pressed in accurately with dies, were quite uniform throughout the entire body production. Among such stampings may be mentioned the side panel which stretched from front to rear, with door openings and windows all stamped out at the same time. It was standard practice in quantity production to have all detail parts, such as window-glasses, upholstery and hardware, made in advance ready for use so that no fitting would be neces sary on the assembling line ; every part had to fit into place with out fail. The bodies were assembled on moving chain conveyors. All parts were placed conveniently at the proper place or se quence of operations and a definite space was allowed for each assembly, permitting no time for special fitting or altering.
Since the quantities produced of one model were enormous, and they were mainly of the same construction, it was possible to build special machines and equipment for each model which could not be used in many instances on another car.
In the automobile body supply plants a high calibre of engineer ing talent had been able, by 1940, to reduce the cost of a body to a point acceptable to great numbers of people, which, in turn helped to reduce costs. (E. G. By.) BIBLIOGRAPHY.-British Aluminium Company, Body Building in Aluminium (5926) ; British Engineering Standards Association, Schedule of Sheet Steels for Automobiles (1924) ; H. J. Butler, Motor Bodywork; the Design and Construction of Private, Commercial and Passenger Types (1924) ; C. T. B. Donkin, Elements of Motor Vehicle Design; a Textbook for Students and Draughtsmen (1926) ; F. X. Morio, Automobile Pattern Drafting; a Concise Course of Instruction in laying out Complete Patterns for Hoods, Cowls, Bodies, etc. (1922) ; James Shepherd, Motor-body Building (1923) ; C. W. Terry, Practical Motor Body Building. A Practical Treatise on the Various Branches of Motor Body Construction, for Coachbuilders, Draughtsmen, etc. (1921) ; Arthur Pound, The Turning Wheel (1934). (X.)