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13th June 1947, Page 50
13th June 1947
Page 50
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Page 50, 13th June 1947 — BUS
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DESIGN

To-day anc Tomorrow

By

1. D. McLintock pRODUCTION of goods and passenger bodies, at the present time of industrial struggle for rehabilitation, is not in a normal condition Many materials are in short supply, building licences for factory extensions and repairs are elusive, skilled labour is scarce and policy is in a great degree determined by the demands of overseas markets.

Within the products of the present day, however, can in many cases be discerned the "shape of things to come " It will be of some interest scan in this light the policies and trends in the field of passengervehicle body manufacture.

With the exception of one or two smaller concerns, bodybuilders have always been a little conservative and have tended towards pure "carriage building." Admirable although such endeavour may have been, it did not keep up with the tempo of the modern age, in which, whether for good or ill, craftsmanship, in the true sense of the word, is on the wane.

Conversion The war, however, wrought a great change. The tale does not need retelling. We all know bow even the most die-hard engineers of the old school have opened their eyes in sheer admiration at the beauty and practicability of aircraft construction on the mass scale.

In a nation notoriously—many say• gloriously—hidebound in industrial production, the commercial body manufacturers were in the first ranks of those who saw the wisdom— indeed, the vital need—of carrying on methods learned not only in the aircraft factories, but in mass production of all manner of necessities from Sten guns to "prefabs."

We find to-day that, although there are still some conservative bodybuilding concerns, most have modernized their products in notable ways, Whilst other companies, far from traditional in their methods, Ltd., Hove, for example, operators, in the main, require something "practical and easily maintained.", It is stated that the 'outstanding or freakish type of design quickly dates in the eye of the operator and the public and the " classic " body is still the most popular.

Interesting points mentioned by this company are that luggage is best carried at the rear in a locker and that there should be interior parcels racks; sliding roofs are not quite sopopular as they were, but internal heating is more so; good vision from all seats is essential, but side roof glasses are a doubtful benefit and may affect strength.

To show that it is not too conservative, however, the company produces an excellent all-metal lightalloy bus body designed for the export market Conversely, the view comes from Saunders engineering and Shipyard, Ltd., Anglesey, that the composite vehicle has grown up, "through British innate conservatism," from the old coaching days, and is being rapidly superseded by more modern methods. This company advocates the careful working-out of stresses, but condemns the use of the panelling as a load-bearing structure in bodies.

There should be greater use of high-strength light alloys in modern extruded forms and proper stressing of various members. Wood screws should be eliminated as afar as possible and noise reduced by the greater use of rubber-to-metal joints.

Some of the latest Park Royal double deckers are of particular interest, in that there is a minimum use of wood and a good deal of use of light metals. Both floors are of -P6-in. aluminium alloy; pillars are of steel with wood inserts for panel attachment. Underframe and waist rails are steel, but longitudinals, the stairway, panelling and roofs are of light metals.

There has been emphasis on the fact that the lower part of a doubledecker is the real load-carrying portion. This results in strengthening it by various methods, and probably in lightening the upper saloon to make up for the extra weight.

In the new Crossley body, a metalframed type, 3 per cent, nickel-steel channel cross-bearers are used for the floor. For longitudinals, up to the waist rail we find 20-gauge steel sheet, swaged and flanged. Additional strength is given by the employment of box-sections, hatsections, gussets, etc.

The Brush bodies (composite and all-metal> have hot-rolled nickel-steel pillars, floor members and rails, instead of the thin sections commonly used before the war.

The Leyland body is all-metal, except for floors, and it uses the " hollow-beam " type of structure and rolled sections of high-tensile steel, well trussed and braced.

In the Roe patent composite body, the full-length zinc-plated rolled-steel waist rails incorporate rubber-filled, interlocked pillar joints. The special staircase is integral with the off side and has two passing platforms In more than one instance, the staircase and rear platform in double-deckers have been given new attention. In the Brush the platform is hung from the upper saloon In the Leyland the staircase is built into the rear framework and takes its share of stresses. The Crossley platform assembly is in the same stressline as the lower body assembly. All

these are indications of a new appreciation of geometry and the science of stress and strain.

Where lower sections are regarded as the load-carrying me,mbers, we find aluminium used extensively in the upper saloons of double-deckers.

Another improvement becoming common to the traditional types of body, as well as the more progressive patterns, is that of connecting the body to the chassis by some means permitting a certain degree of flexibility. The reasons are so obvious as to make one wonder why this idea should not have been adopted earlier.

There are various methods of connection, most of which rely upon the use of bonded-rubber linkage of some sort, but there is varied opinion as to whether to allow the whole structure to flex or whether to anchor it firmly at one or more points, Thus, in the M,C.W. body, intermediate bearers are permitted to flex, but not those at the front and rear. The Brush body is rigidly fixed only at the rear bulkhead.

Prefabrication or semi-prefabrication can be seen to a great extent in the case of metal bodies. For the Crossley metal-framed types, interchangeable sub-assemblies are built on jigs. Duple bodies are, in many" cases, built up from jigged parts; a Duple export prototype was made for bodies which could be shipped in parts and assembled by unskilled labour.

One of the latest developments—a large-scale one—is the fabrication of complete sets of parts for bodybuilding. This specialized industry has been organized by the companies forming Tube Investments, Ltd after co-ordination with bodybuilding interests.

The Park-Royal-bodied Commers for B.O.A.C. arc built from parts prefabricated on compressed-rubber dies All body parts are easily replaceable when these methods are employed. Repairs are much easier and cheaper, and far less skilled labour is necessary.

Pop-riveting is now employed in nearly all metal bodies and has come to stay, as has the use of so many of the comparatively complicated metal sections and junction units. Even trimming, interior decoration and seating have undergone changes. Plastic trimmings are widely used; garnish rails and mouldings are sometimes of pressed-metal sections; crackle finishes and simulated grained leather by the treatment of

paint are seen; seat frames are often tubular.

Overseas, some bodybuilders have looked farther into the future. From the American Twin Coach Co. comes a streamlined " semi-monocoque" constructed luxury coach. It has a "structural-belt" member just below the window line. Multiple stresses are distributed, even the panels taking some of the load.

In France, handsome streamlined coaches were built by Floirat, at St. Denis, to help solve the country's acute transport problem. The concern broke all records, showing that beauty and revolutionary construction do not mean loss of speed in meeting heavy demands. These " auto-dynamic" bodies were built on frames of metal tubes in various sections.

What does the future hold? Some people say chassistess construction is the thing, in which' case new techniques have still to be evolved. A nimble hare has already been started by t he Beadle frameless body, in which units are accommodated in a light-metal structure based on four main longitudinals with deep crossmembers, and the superstructure is laid on " hoops " of H-section extrusions in light metal.

On the other hand, according to Brush foachwork, Ltd., interest in

the chassisless ,vehicle does not yet appear to' .have; crystallized in this cottntrV because of the.difficulties of building double-deckers of this type, especiallY if the under-floor engine— a Brush-B M,M.0 conception—were used Mr Bullock, of the Brush concern,. thinks that chassisless single-deckers seating 45 passengers will, perhaps, eventually, supersede the present orthodox types

Similarly, James Whitson and Co., Ltd., West Drayton, Middlesex, suggests that the method cannot at present be seriously considered, because large-quantity production would have to be assured.

Others say there should be something less' revoltitionary, yet 'more progressive than most of to-day's bodies. A near approach to what they desire might be, for example, the Duple export body, in Which the under frame and floor are a " raft "

unit. Opinions may vary on this matter.

Whatever may be the trend, it seems certain that prefabrication, aircraft structural technique and the study of theoretical body-architecture will be carried on. Psychological and :esthetic factors, and what the Americans call custom-building, may come later, whilst there will be added progress on established lines when further materials become available.

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