THE USE OF METAL FOR BUS BODIES.
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A Paper on an Interesting Subject by a Graduate of the Institution of Automobile Engineers.
reN March 12th Mr. W. Swallow 14.../read a paper entitled "Metal Omnibus and Car Bodywork" before,London graduates of the Institution of Automobile Engineers.. This dealt briefly with the items to be taken into account by the designer of this class of coachwork.
The author stressed the advantages of using metal for body construction and showed a preference for the unit type of design, that is, making the lower part of the body integral with the chassis.
In dealing with the four methods of body suspension, Mr. Swallow pointed Out that unit construction gives light weight by reason of its simplicity. Three-point suspension is only applicable to small buses as the local stresses are otherwise too great on the mouutings. Two advantages of this method are lightness—the body has very few stresses to withstand—and it can be finished before mounting. When semi-rigid mounting is employed, the body is insulated from a certain
amount of the chassis deflection. • Where sheet metal is used the aid of press tools is essential if the quantity of parts justifies the installation of the plant ; if the numbers be email, care must he taken b enable the majority of components to be folded by hand or beaten out. Pressed box channel or folded sections can be used for framing, provided that efficient means be taken to avoid corrosion.
In another type of construction, extruded, rolled or east sections may be utilised. Steel tubing can also be need for framework; internal Corrosion must again be prevented. Angle and T sections of steel and aluminium alloy offer many advantages; steel permits easy welding, but aluminium alloy calls for riveted or bolted joints.
For calculating the body stresses, the author advocated that only the ordinary passenger Iced be regarded as a basis, allowing the factor of safety (five was that quoted) to take care of any overload. In the case of a double• saloon bus, the body weight assumed was I cwt. to 1 cwt. per seated passenger.
Wood fillets for the attachment of fittings and furnishings can largely be avoided if self-tapping screws be used for the metal bodywork. Drumming of panels can be obviated if canvas or thin cork be pasted on the inside of them. For interior panels, leather cloth serves the same purpose, as well as providing a covering. Asbestos, cork or Balsam wool can be made to give good insulation from heat and cold, whilst double panels for the roof are very effective in tropical climates for excluding excessive heat.
• We deal with the topic of metal bodywork elsewhere in this issue. n45