How to Reduce
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BODY WEIGHT
Unnecessarily Heavy Coachwork Greatly Increases Petrol Consumption and places Added Strain upon a Vehicle; in this Article our Bodybuilding Expert Outlines Methods of Saving Weight in Coach and Bus Bodies, without Sacrificing Strength and Stability
EVERY bodybuilder whose output is sufficient to justify the expense of such an installation should have his own weighbridge, or, when the opportunity occurs, should make use of one in the neighbourhood. He may then keep a record of body weights in their relation to seating capacity, and to the leading varieties of design and construction.
The private weighbridge is the better investment, because it gives more opportunity for weighing a body separately, or, what is more important, during its various stages of construction. It should then be possible to decide what items chiefly influence weight and in what directions economies may best be effected.
The approximate weight of a bus or coach body is 1 cwt. per seat, but there are wide fluctuations, especially as the seating capacity increases. A modern 48-seater enclosed-top double-deck body weighs about 46 cwt., although some builders claim to economize that amount by as much as 4 cwt.
When these figures are compared with those for a double-decker having an enclosed upper saloon, but with an open staircase, the difference is about half-a-ton. A 32-seater service-bus body may weigh some 28 cwt., whilst the greater luxury of a coach of the same seating capacity may increase the weight of the body by nearly 4 cwt.
Now that the maximum weight of a fully laden four-wheeled singledecker may be 9 tons and a doubledecker 10 tons, with a total weight of 12 tons for the six-wheeler, the necessity of complying with the law has eased considerably the difficulty hitherto experienced of keeping the weight within the limits imposed.
But the bodybuilder who is jealous of his reputation is chiefly concerned to reduce weight, because a superfluity is not only wasteful but it is an indication of poor design. It has also an influence on running costs.
It is estimated that a saving in weight equal to 30 per cent. will reduce the petrol and oil bill by half that percentage. When the annual mileage of a large fleet, or even that of one vehicle, has to be taken into consideration the saving effected is certainly worth while.
It is no easy task to overhaul any design of body for the purpose of saving weight. Rigid simplicity of design and finish may solve the problem, but such a scheme would be at variance with what the riding public has been educated to expect.
If weight is to be saved it must be done by comparing the strengths of various materials with their respective weights, as well as by applying a knowledge of mechanics, so that the material used may be arranged to the best advantage.
One of the most successful means for reducing the weight of the body is the use of aluminium alloys instead of wood for constructional purposes, but up to the present such methods of construction have been adopted only by specialists. The increased use of metal depends to a certain extent upon the degree of standardization that is possible.
Amalgamations of existing fleets would tend to encourage such a policy, especially when extensive renewals have to be made. It would, however, seem that those who are the most enthusiastic supporters of standardization are also the first to introduce new designs. Probably the research necessary to create a good standard type of body is also a means whereby many fresh ideas are evolved.
In the majority of instances, if the bodybuilder would seek to save weight, it is chiefly a matter of improving, with this object well in mind, the composite form of wood and metal construction. The sheetmetal corner bracket and the hitching of cross-bars, pillars, hoopsticks and seat legs are now so widely adopted that they are regarded as the usual practice.
Regarding the wood framework itself, a certain sectional area may be necessary at joints, to accommodate glass runs, or to give a certain shape to the panelling, but there are also many other parts where the timber may. be lightened without sacrificing strength or impairing the attractiveness of either the exterior or interior finish.
The bodybuilder is, as a rule, unable to save weight by using woods other than those commonly adopted, because the strength of timber is usually directly proportional to its seasoned weight. At the same time, it is considered that both ordinary and armoured plywood have not yet been utilized to the utmost advantage.
Weight is saved in the mounting and bottom framework of the body when the chassis is of maximum width, or, better still, when outriggers, which afford support for the full width of the body, are provided.
Although a floor placed as close to the chassis as possible is desirable if weight has to be specially studied, if the floor has .to be raised to make a luggage locker, or to eliminate wheel-arches, the floor supports should be of box or lattice-girder design.
It is always an advantage if the body framework can birtbraced by means of diagonal struts or tie-rods. Such braces should be preferably of rustless metal and adjustable.
An appreciable saving in weight is effected when the inside casing boards are omitted, such as is possible when either half-drop or horizontally sliding windows are adopted. The omission of the inside roof panel is at present not likely to be approved, because it is regarded as a recent refinement There is a wide variation in the weight of seats, which is not always justified by reason of the degree of comfort afforded.
If only a few lb. per seat can be saved it is worth while, because with a normal double-decker a matter of 4 lb. or 5 lb. less per seat will make a difference of about 24 times that amount when the weight of the complete body is considered.