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MAKING A BODY
By W. S. Attwood
NOW that mass-produced commercial bodywork has become an accomplished fact, it will probably be of interest to operators to know something of the relative details of this type of coachwork as compared with the " individual " or "handmade" products which previously held the market. Having had some 15 years experience in the design of both types. I hope to present an unbiased study of the methods of design and construction relative to the two classes.
From the days when all bodies were made by hand, we have evolved to the present stages where it would be impracticable to follow this procedure. Even so, there still is the need for the hand-made body and there are those in business to make it, quite as expertly as the craftsmen of the earlier days.
The Onus of the Bodybuilder.
As road transport has developed, so has it been possible to standardize the types of body which are suitable, if not ideal, for the majority of uses. There are numerous laws and restrictions which have to be faced by present-day manufacturers. This remark applies particularly to the limits of unladen weight, the onus for meeting which falls, in almost every case, on the bodybuilder, whose job of finishing and mounting the body forms the last operation.
A little more co-operation between chassis manufacturers and coachbuilders would go a long way towards lightening the'burden of the latter, and towards avoiding the dangers which may result from the skimping of the bodywork in order to save weight.
In one sense, the introduction of the Road Traffic Act, 1930, was a great help to the coachbuilder, standardizing, as it did, the constructional requirements for every area. Prior to this, every local council or police department made separate restrictions, and I have recollections of quite an elaborate filing system containing these by-laws and police regulations, although they mostly concerned pasenger-carrying vehicles.
Manufacturing Methods.
Most coinmercial bodywork can, to-day, be placed in one of two classes —hand-made or mass-produced.
Generally speaking, the present-day coachbuilder relies on the operator who wants a body of different design or dimensions from that which can be obtained as standard from the chassis manufacturer. Very often the operatot will ask for elaborate details to be incorporated, the weight to be such that the vehicle will come within a certain limit of taxation, and, perhaps,
finally he will want to pay a price very little higher than that of a standard body. In addition, I have many recollections of customers insisting on delivery in a week or less. Whilst the poor coachbuilder does his best to comply with all these requests, he, cannot be reasonably expected to pioduce a sob, either to his own, or to his enstomers' satisfaction. In my opinion, the great point to be remembered in ordering a special body, is to allow ample time and to leave as much of the detail as possible to the coachbuilder, whose experience in constructional detail, especially, will be of great benefit to the ultimate reliability of the vehicle.
Preparing the Patterns.
A brief summary of the operations involved in the production of the body might be useful. After becoming acquainted with the type of body, the work expected of it, and the Emit of weight required, the coachbuilder will submit a scale drawing showing the general design and leading dimensions, together with a specification and quota
tion On acceptance, the draughtsman will get busy with a full-size layout, from which patterns will be prepared for all shaped framing parts.
After being roughly prepared in the mill, all straight and shaped timber then passes to the marker out, whose job it is to mark each piece for machining-out mortices and tenons, hall-laps, grooves, rebates, etc.; in fact, the more thoroughly his job is done the quicker will the body be put together. While the timber is .being finally machined, the ironwork and panelwork will be proceeded with so far as possible, together with the numerous other items such as upholstery, glazing, window frames, finishers, etc., all from information supplied by the drawing office.
The parts will then be transferred to the body shop, where a gang of erectors will proceed to build the job direct
on. to the Chassis, if it be available. At this stage, the designer will keep a close eye on the work if weight be an important factor, to make sure that the dimensions of body brackets and reinforcements are kept down to a minimum.
Having built and panelled the body, and overcome the numerous little difficulties which usually crop up in mounting, the job is passed through to the paint and finishing shops, and, finally, collected by the customer. On completion, the designer will, perhaps, breathe a sigh of relief when he receives the weighbridge ticket showing that the vehicle has just 5 lb. to spare.
The Gamble of the Special Body.
The coachbuilder, if restricted by weight, will usually err on the heavy side—a good point in one sense, although, to the operator, unnecessary weight means loss of revenue. On the other hand, if the available weight allciwanee be small, the body may lack in its inakeelip the Material essential to its lone life. The gamble taken with the relbility of a special body varies Mainly in proportion to the degree in which the design departs from standard principles, because in many cases it will tend to become an experiment.
' Mass-produced bodywork is usually scorned by the coachbuilder as lacking in craftsmanship. This may be true so far as individual skill is concerned, but what matters so long as the article produced is suitable for its task?
In contrast with the hand-made body, the brains of the designer and skill of the craftsman are expended in the experimental stages, and the body is produced to conform with these ideas as closely as machinery and production methods will allow. A brief outline of the work carried out up to the production stage of the body will not be out of place.
Submitting the Experimental Body.
After an exhaustive study of the most suitable design and size of vehicle to be produced, a full-size drawing is prepared and an experimental body made, much on the same lines as that described above. This is then mounted on the chassis, and submitted to the heads of the various departments coneemed with the sale and service of the vehicle, for criticism as regards design, general utility, etc.
Assuming that the body has to be modified a few times to meet these criticisms, some months may elapse before the engineering department is able to get going on the constructional side. The draughtsman, working in close co-operation with the chassis designer, gets busy on a full-size draft of the body—drawn on a sheet of cellolosed aluminium to ensure accuracy— details are carefully thought out from all angles, and each part carefully considered for weight.
From this data, two or three trial bodies are built. These are mounted on the chassis, and then tried out on the road under varying conditions of loading, etc. During the trial period, which may last several months, a careful record is kept of defects in construction which, almost invariably, are revealed, and the body (and drawing-office records) are modified accordingly. When the desired state of perfection is reached, all the detail drawings are released, and the production department proceeds with the jigs, dies, tools, etc., necessary for manufacture on a large scale.
Constructional Contrasts.
This is, of course, a costly business, as the method of manufacture forms a striking contrast in speed when compared with the orthodox coachbuilding routine. A master pattern of every timber part is made, and every machine in the mill is specially adapted and provided with jigs for machining the parts, down to the most minute details by the thousand. From the mill these are sent in batches to the sub-assembly jigs, where roofs, sides, underframes, etc., are assembled, and all joints .glued and screwed, in a matter of yninutes.
The final assembly, which is carried out on a moving track is also, in itself, a study in speed and efficiency. All parts such as panels, brackets, pressings, complete doors, windscreens, seats, etc., are prepared in batches in the various departments, and are all to hand at the moment required by each workman "on the line," who has his own particular job. One of the main factors in efficient mass production, is that every part is correctly made so that on assembly hand work is completely eliminated.
When completed, the body is lowered by hydraulic tackle on to the chassis. and the whole operation of mounting, including wings and running boards, occupies, perhaps, about five minutes. In view of the elaborate tests which precede construction, it is clear that the operator has every reason for con. fidence in the reliability of the massproduced body.
Risks that are Avoided.
It will have been designed under good conditions with regard to cooperation with the chassis designer, and the time allowed for development will have eliminated all risk of overweight, or, alternatively, failure of any part through "skimping."
If firnber framework be employed, there is no doubt that the lack of craftsmanship employed in the jointing and assembly will make it inferior to the hand-made body. This, however, is usually compensated for by the useful, scientifically designed pressings and brackets, which can be produced only for large-scale fabrication.
a34 Another point well worth bearing in mind is that replacements of any part can be obtained quickly and at reason. able cost.
Paint and varnish are still commonly used by coachbuilders and, if used .properly, that is with a time allowance of at least a week, will produce an excellent finish. A cellulose finish can be obtained only if all wood parts be metal-covered.
The panel work on a mass-produced body, coming, as it does, straight off the presses, provides a surface so nearly perfect that hardly any filling is required to cover the defects which inevitably occur in most hand-beaten panel work. For this reason, a coat of synthetic priming, sprayed on, is the usual standard finish, the painting, if required, being left to a coach painter. On certain types of massproduced body, that is, those which are either all metal or entirely panelled in metal, a cellulose finish can usually be obtained at a small extra charge. Owing to the elaborate plant usually available, this can be relied on to be a good and durable finish.
The huge quantities in which the materials for a mass-produced body are purchased account largely for the lower price. Consistency of quality is, therefore, an important factor which should be considered by the operator in placing a repeat order.
The coachbuilder is at a disadvantage, in that, being unable to forecast his requirements, he cannot carry a large stock of raw materials. Consequently, he has to buy small quantities at short notice.
The Semi-mass-produced Body.
There is another class of body which may be styled " semi-ins ss-producgd," that is the body which is supplied as standard by the chassis manufacturer, but Manufactured by a coachbuilder. Owing to the relatively small number called for, the cost of elaborate production machinery would not be justified, although the coachbuilder, knowing that repeat orders will , be coming along, is able to commence building in advance and to prepare his material in batches to ensure uniformity.
This type of body should possess the best points of both the previously described types, as it is built in collaboration with, and tested by, the chassis manufacturer before being put on the market. It provides a steady flow of work for the coachbuilder whose men can get accustomed to every constructional detail, and any risk with regard to overweight or faulty construction has been overcome at the outset.