The principles of automobile body design

The lack of information on automobile body engineering and the demand for reprints of the articles which were published in "Motor Vehicle Monthly" led me to re-arrange and re-write these articles so that they could be incorporated in book form. Body engineering has made tremendous strides in the last few years and the writer has endeavored to collect all the data possible which would interest the body engineer and the student.

The possibilities of this profession are very good, and it is hoped that the book will be of help to the student as well as the engineer. The scope and aims of the body engineer were outlined in a paper by the present writer, read before the Society of Automotive Engineers, in New York, January 12, 1921, and the following extracts will make this preface complete:

In choosing the title for this paper it was hoped that a note could be struck which would bring to the attention of the industry the broadness and scope of body engineering. Also to outline the way this side of the industry can best be considered and developed. Body engineering has, of course, to look for mass production or big business for its greatest encouragement. This is the age of big business, and the automobile industry is a big business, in fact one of the biggest, and not far from being actually the biggest in the country. Big business makes demands for organizations which the small business does not need. Small items in a small scale production can be easily handled, or they about handle themselves. Small items in great production are of tremendous importance, for as a chain is as strong as its weakest link, so is big business.

If a thousand cars are made in a day and a shortage occurs in one of the smallest items it is possible that the entire production is held up, incurring the loss of thousands of dollars. This emphasizes the point of importance of every detail in large business in a way which no one can fail to grasp. For instance, if a change in design could be made by the body engineer that would permit cutting the leather for the trimming to 15 per cent, waste instead of 20 per cent., a saving of $1,000 and over per day would be made on a car production of 1,000 cars per day. In a small shop or custom shop a few feet of leather more or less would not make a difference, but it means so much in a large production that this and every other detail must be considered very carefully.

Body engineering is really a broader field than the title conveys, as will be shown in the outline of this paper. The body engineer's relation to a body manufacturing plant, a large car manufacturing plant, a small car plant and a custom shop demands different classes of engineers. In the main, the body engineer is responsible for the external appearance of the entire car. If it is a custom-built car, a preliminary sketch of the complete car is made and very often this is all the body builder, top maker and trimmer has to work on, so he gets the car to look as nearly like the sketch as possible. A body plant very often submits designs for a complete car, but generally has only the body to build. In order to work out his ideas or combinations of ideas the body engineer of the small plant relies, to a great extent, on the companies which make his bodies. In a large plant where bodies and all other metal parts are made, the body engineer has to consider the manufacturing details involved in all parts that he designs.

Just to cite an instance: There is a distinct difference between the mechanical side of the automobile and the general appearance or the artistic side. No one would ordinarily combine the story writer and the illustrator together in more than a co-operative spirit. The success of the story does not depend upon the illustrations, or vice versa. But having a good story properly illustrated gives a wider field for its sale.

So it is with a car; the mechanical condition and limitations have to be taken in hand by the body engineer, and it does not stretch the point at all in saying that its first qualification must be an artistic one. The proof of this statement is demonstrated in the 1921 cars now being displayed. The body engineer, for the company specializing in custom body work, must apply artistic principles to every car he has to create, each car, calling for individuality of its own, draws heavily on his power of creation. But the body engineer for the large production has to satisfy 100,000 people with perhaps one design. There is a distinct difference between that and satisfying the individual as the custom engineer must. Now we know that the tastes of 100,000 people are not all the same even though some of our movie stars have practically an unlimited following. The design then for the 100,000 is not the bizarre design, but one that will come as near as possible to being acceptable to the majority.

It is often remarked that the so-and-so car does not quite suit the person talking and invariably he remarks that there is a certain characteristic that he favors. Take several such individuals and see what all their ideas pertain to and it will be found none will agree on any specific design. But if a car of established popularity is shown practically all will be satisfied with it. The point to make is that the simplicity of the car's design and absence of jarring notes can only be evolved by painstaking effort. The layman cannot appreciate the work behind the smooth finished product, as the effort is not as apparent as the finished carvings on historic buildings and churches that show the effort required by their intricately embellished carvings.

Art in the generally accepted term applies to pictures, carvings, etc. Art as applied to an automobile has to be manifested in the arrangement and shaping of sheet metal units on frames. The requirements of art have one other standard to match up to, and that is, can the result required be accomplished by economical manufacturing? One thousand cars or more a day do not allow for fancy hand decorations or carvings. Art has to be satisfied by huge metal presses and metal forming machines. To achieve results the practical side of the body engineer must be as heavy as his artistic side, as they must work hand in hand to avoid disappointment. While we have definite lines upon which the artist bases his work, his success does not depend upon geometrically arranged lines, nor can the composition of his pictures be worked out with a slide rule. The mechanical side of the car is quite amenable to slide rule practice, but the body lines are not. This is one of the reasons why body engineering has an indefinite position in the industry.

In large production it is not even possible to control the metal parts to a very fine degree owing to variations in the grades of metal and fluctuations in the presses. The upholstering, top design and painting, including enameling, all have bearings on the final results and have to receive the attention of the body engineer. The main trades which govern the body engineer's work are wood working, sheet metal working, metal machine work, braces and hardware, trimming, top building, painting and enameling. As the practical side of the engineer is emphasized, he should be familiar with all these trades and they are all peculiar in being professions that cannot be learned by correspondence courses. In fact there are practically no schools or instruction books covering the modern phases of this work.

The body engineering department could be divided into six main divisions as shown in the following layout:

1. Body construction, open and closed.
2. Sheet metal, body metal, fenders, hood, radiators, etc.
3. Trimming.
4. Top building.
5. General hardware and mountings.
6. Painting and enameling.

All these arts covered by the six divisions dovetail into one another and must be considered in the preliminary design. For instance, the radiator and hood can really be considered the starting points for the car body design, and when these are established the main body construction is worked out for the dash or cowl line back.

The exterior lines of the body must be pleasing to the eye, at the same time the passenger capacity has to be arranged to give ample room and comfort to the required number of passengers that the body is being constructed for.

In order to give ample comfort, satisfactory trimming has to be arranged for. Comfort depends on leg room, body room and positions, and well arranged cushions and back springs with soft padding, with suitable cloth, plush and leather covering. Passing on to the top, if it is an open body the lines and windshield must be considered in order to permit a top to be made that will give adequate protection and at the same time be pleasing in appearance and of course harmonize with the rest of the car.

The fenders and side aprons and radiators and mud pans can add or detract a lot from the car's appearance, and must be worked out to blend with the other larger elements in the car craftsman's shift.

Under general hardware comes a lot of small parts, such as window regulators, door locks, windshields, hinges, etc., not very large in themselves but important in providing ease of operation and satisfactory service to the car owner. What is there more annoying on a car than defective locks, rattling doors, and hard-working or leaky windshields. And last but not least comes the painting, and when this is properly done it adds tremendously to the final results. In working out the design the panels, molding and corners should be made so it will simplify painting. Modern mass production methods use sprays and flowing operations, and if there are bad corners, mouldings and holes, these will seriously interfere with the paint, and cause varnish and dirt runs. If it is planned to have molding arranged in different colors from the main panels they must be arranged to give harmony and not produce discordant lines.

In the foregoing I have endeavored to show the broadness of the body engineering field of effort, and as the production increases the detailed accuracy required along these lines becomes more and more necessary. It will require organized departments to be able to handle this work. The grouping previously referred to can be made into department divisions. This can be controlled by a separate engineer, if the amount of work warrants it, and one or more men to keep the work in progress. A general drafting force with chief draftsman and checker are also required.

Modem accounting and production system demands detailed information about every piece which goes to make up a car, and this entails a lot of detail drafting work. Every piece of wood, top material, side curtain material, reinforcement and wadding, trim material, leather, imitation leather, binding; ounces of hair, tacks, nails, etc.; every screw, nail, pieces of hardware. This means engineering information is required with blue prints and specifications. The old method used to be to make paper patterns of all parts and let the manufacturing departments control their own work, and whenever duplication of parts was required, additional paper patterns were made and sent out. Long ago it was found that no progress could be made in manufacturing without proper engineering records and blue prints. I venture to say that there are several modern auto plants that have no definite engineering control of the material purchased and fabricated in the groups outlined, and this material runs into millions of dollars per year.

While the art of coach building is as old as the ages, it was brought to a manufacturing basis only a few years ago when buggy production hit its high mark. The advent of the automobile brought up entirely new problems and the automobile body engineer is practically a recent accession to the engineering profession. The importance of the body engineer can be measured by his designs and by his control of the materials and fabrication of the material required on the automobile body. It is not sufficient that a beautiful and readily marketable design be produced, for it must also be possible to make it economically and without waste of material.

The future holds out big opportunities for the body builder and engineer. Competition will be keener than ever, not only among the body manufacturers, but also among the car manufacturers. The automobile competition will be the body engineer's opportunity. With the stabilizing of chassis construction, the external body and allied construction will become one of the biggest factors in marketability and stimulation of sales.

Painting comes under body engineering, but the subject is such a broad one that it would require a volume by itself, so it was thought advisable to omit it from this book.


CHAPTER I - EVOLUTION OF THE AUTOMOBILE BODY

Since the time when the first gasoline engine was adapted to the road vehicle, the progress of development of the mechanical features of the automobile has been rapid and sure, while the exterior features of the car, which can be classed as the running gear and the body, did not keep up with the development of the chassis. When the chassis and engine had been brought up to a high degree of efficiency, attention was brought to bear upon the body and other features of the car that had any reference to the comfort of riders and the improvement of the car's external appearance.

The possibilities for many improvements were soon noted and acted upon, the result being that the automobile departed from the ways and appearances of the horse-drawn vehicle and took on a distinctive style of its own.

The change was revolutionary, as the passenger-carrying conveniences had been designed by basing the construction on the experience gained in making horse-drawn vehicles, and the new design and construction called for altogether different conditions.

A new industry of vast proportions was created which had to develop new machinery and new methods to cope with the requirements of the automobile body and its component parts. The methods used to manufacture only a few years ago seem crude when compared to the methods that are now in vogue; also, the costs were high compared to the new costs. New industries have sprung up so quickly around some of the component parts that the great majority do not know about them, as few have had time to write about or describe them.

The various phases of development in the body and the running gears, as the other parts are called, will be dealt with briefly in this volume. These parts have now arrived at the stage where improvements are hard to make and new designs are hard to create, and when this stage is reached, analytical study is required to accomplish any further improvements. Progress is generally made by basing new developments on previous practice, and if the early developments are not known, the work is carried on upon an insecure foundation. The aim of this book is to furnish the foundation so that past results can be considered while new ideas are being developed. That the time is here when a new field of effort is opened up is demonstrated by the cars of 1921 and 1922, as shown at the automobile shows. These shows could be classed as body shows, because the important developments shown in the cars over the previous season were in the refinement and improvement of the body design, running gear and
equipment.

America's methods of manufacture have done a great deal toward the development of the automobile, as they have produced cars in vast numbers and at a price that brings them within the sphere of the majority of people. The result is that the cars are built in great quantities of one design, as this makes it possible to develop ways and means to produce cheaply. The development of the automobile must necessarily hinge around that class of car that manufactures in quantities, and not around the special hand-made production. It requires a great deal more work to develop a car for quantity production than it does to make one special car. Every detail must be considered as every penny counts when the quantity produced runs into the thousands. There are greater possibilities in the design and production of the manufactured car, consequently most of the work in this book has been done with large production in mind, but of course there are many of the problems which apply just as well to the sample or custom car as they do to the quantity production one.

It is very interesting to trace the development of the automobile body from its early stages up to the present beautiful streamline designs. The first model, dated about 1903, consisted of a box-like structure with two seats on it, conveniently located adjacent to the steering lever or wheel. In Fig. 1 is shown a line sketch of a typical body of this period. This would be considered in present-day terms as a roadster, and is the prototype for our present two-passenger cars. Between the above period and 1905 a variety of body types were made and accommodations for two additional passengers provided. Some of these four-passenger bodies had a door at the rear for extra passengers to get in and out; this did not prove satisfactory, as it cut down the room for a back on the rear seats, and the passengers had to sit face to face, making it almost a jaunting car effect. It will be noted that a great many corners and mouldings are provided. The design savors a good deal of the horse-drawn vehicle, to which a buggy type of top is fitted. The car shown for the 1908 period in Fig. 3 has a body that is very similar to the 1905 period; the only difference is the slight improvement in outline and detail, and a smoother line is shown throughout the design. In the 1912 style shown in Fig. 4 is seen the advent of the "four-door" type, and a windshield fitted as permanent equipment. The four-door type of body marks the coming of an "automobile" body and the breaking away from the buggy and kindred horse-drawn vehicle types. This body has capacity for five passengers, and has four doors.

The 1914 models show the streamline type of body. This has five-passenger capacity and four doors that operate. The windshield brackets are set on the body and make the windshield a permanent part of the car. The dash is made smaller and the hood larger, so that the two are of the same size and present an unbroken line from the radiator to the back of the body. The name "streamline" dates from this period when the bodies were made to match the front of the hood and present a clean, smooth appearance. The title "streamline" has been much abused, as anybody that eliminated the offset hood and dash took that name. Boatline would be a name that would be more descriptive of the style, as the front end of the car is always the narrowest part, as in a boat shape. See Fig. 5, which illustrates a boat shape. A true streamline shape would take on the proportion of a fish or torpedo, the widest parts of this being the front end, as shown in Fig. 6. The theory of a true streamline body is that it will go through the atmosphere with the minimum degree of resistance ; the air displaced by the maximum cross sectional area must be permitted to close back again without creating a vacuum. This is accomplished by the tail-like end of the fish or torpedo body. This is illustrated by the lines that are shown outside of the torpedo-like shape in Fig. 6. These lines represent air, and show how the air is parted easily and allowed to flow back to the natural condition gradually. In Fig. 5 the lines will be seen to leave a gap at the end of the body. This is a vacuum that this style of body would create, and has a tendency to pull the body back. In Fig. 7 is shown a representative shape of a touring car body. This, it will be noted, has a decided wedge shape, and a vacuum creating back. It is obviously impractical to adapt the torpedo-like shape to a touring car body, so that as a comparative name the term streamline is a misnomer. For the 1916-17 period, Fig. 8 shows the approximate type of car that is so familiar now. This has the long, straight lines, with a hooded front set back. This tends to smooth down the necessary projection of the seat back and give the appearance of a continuous line along the top of the body. The projecting wind shield brackets are also eliminated, so that the windshield attaches to the body without any unsightly projections. This brief review of the body developments describes the periods when these changes went into general effect on the American cars.

Some makers can claim that they had any one of these types several years previous to the times stated, and this may be true in a few cases, because up to a few years ago the European designs were followed by the majority of manufacturers. Consequently the general American styles at the beginning of the great war were several years behind the European ones. Since that time we have more than caught up with European design.