Mass Production of Bodies

MASS PRODUCTION OF BODIES In America the concentration of automobile production in a few factories soon eliminated the small workshops scattered throughout the country and resulted in the development of large body-building units either within the plant of the chassis manu facturer or nearby. Piece by piece, the wooden side panels were replaced by steel or aluminium panels in order to secure better and more durable painting, until finally the entire body was covered by pieces of sheet steel. About 1912 this sheet steel was first drawn into large units. These parts were attached to an inner wood frame and were simply a skin superimposed on the body it self to receive the finishing coats. Some manufacturers still use this outer steel shell over an inner wooden frame.

Steel Body.

About 1915 what is known as the "steel body" was developed. In this design the same outer shell was flanged inwardly at the top and bottom edges and around the door openings and was reinforced on the inside by certain metal mem bers riveted or welded to the outer shell. The wooden posts, sills and braces were omitted. These two types of construction were used in the manufacture of what are known as open or touring car bodies, the solid framework extending up about in or i2in., above the level of the seats. In each case, the body was a distinct member from the chassis, having its floor integral with the sides, and fastened to the chassis frame by bolts. Until about 192o a great proportion of automobiles carried such a body. Protection from the weather was by fabric tops which were generally collapsible and by removable side curtains.

Closed types of bodies which could be manufactured by Amer ican methods at reasonable costs were developed soon after the World War. This closed type of body has gradually superseded the open type. The demand for great quantities of bodies at moderate cost has necessitated development of ingenious methods of manufacture to reduce costs. (See MASS PRODUCTION.) This need for reduced costs, together with the necessity for stronger bodies to keep pace with the development of more power ful motors and increased speed, resulted in the all-steel, or mono-piece, body. In this body, which has a soft roof, all the parts are welded into the whole. The entire front—hood, dash,

windshield opening, front edge of roof—is formed of one sheet of steel. The entire back, from the bottom to the roof, is made of a single sheet of steel. The entire side is made of one piece of steel with the door openings formed in. This construction has made possible streamlined, and partially streamlined, designs which are now almost universal.

One of the latest and most interesting developments has been the "mono-roof body" which is assembled from four major units. The all-steel roof of this body is a single stamping—probably the largest stamping that has ever been made—in which are in cluded the windshield and rear window openings and the cowl top panel. This roof forms the keystone of the arch to which the two side panels and the rear panel are spot-welded into a homoge neous steel structure of the utmost rigidity and strength. This formed arch not only greatly increases the strength of the roof, but, by stretching and permanently setting the metal, it prevents vibration and drumming. Furthermore the graceful curve formed into the roof panel makes possible the blending of the lines of the car into a streamlined whole.

From the standpoint of assembly, this body has a great advan tage in that flash-welding is almost entirely eliminated by spot welding which is more readily adapted to assembly operations in branch plants.

Upholstery.

Trim and upholstery are securely fastened to paper cord which is attached to grooves in the metal reinforce ments. This cord is used because it is silent under all conditions, is lighter than wood and does not splinter or burn.

Painting.

The use of varnishes has been almost entirely superseded by the use of cellulose coatings. This is commonly applied by means of pneumatic sprays, several coats being ap plied as the body moves along the conveyor lines. The coats can be applied one after the other at intervals of 15 to 3o minutes. In the interim, from one spray to another, the bodies pass through ovens where the drying is hastened and the lacquer is somewhat hardened before receiving the succeeding coat. After the several coats have been applied they are polished by vigorous rubbing on the part of the operative. (E. G. Bu.)