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BUS-BODY Cc

24th March 1933, Page 50
24th March 1933
Page 50
Page 51
Page 50, 24th March 1933 — BUS-BODY Cc
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Which of the following most accurately describes the problem?

JSTRUCTION

with an eye o longevity

The Effect of Municipalities' Strict Conditions on Body Design. Current Methods of Building Coachwork for Buses THE modern bus body is lightly built in order that the vehicle shall not exceed a certain unladen weight. Lightness of construction is desirable also because the weight of the bodywork, or non-paying load, is then as small a proportion as possible of the gross load. The weight of the body per passenger seat, for either a singledecker or a double-decker, has been reduced to about

cwf.

Fuel consumption Is affected not only by the weight of the bus and its varying load, but also by its wind resistance. Attention should be given, therefore, to the elimination of recesses which form air pockets and the reduction of the area of vertical surfaces at the front.

The true test, however, of the quality of the bodywork is its durability Riad cost of maintenance. The last-named item is influenced also by road conditions, driving efficiency and garage organization.

The municipal authority, when Inviting tenders for the supply of bus bodies, takes every precaution to ensure that they shall be well built. A detailed specification is supplied as a basis of the quotation, or, if the bodybuilder submits his own, it must give definite particulars as to materials, methods of construction, equipment and finish, also facilities must be granted for inspecting the work at any stage of Its assembly.

The somewhat rigid conditions enforced by muncipalities has the effect that such work is regarded as of special quality.

B36 Much success has been achieved in reducing weight and wind resistance, so that the building of a bus body that shall withstand hard wear and, apart from accidents, cost little to maintain, is chiefly a problem of deciding what method of construction shall be adopted. . Bus bodies have a hardwood framework with metal panels and strengthening plates, or metal components take the place of the wood parts in varying amounts, until the all-metal type of body is reached.

The wood framework may be of ash, oak or teak. Each variety or timber has strength, but ash is used because of its flexibility, oak because it resists moisture, for which reason it is usually confined to the bottom of the body, whilst teak is not liable to the attacks of insects.

In order to keep the floor close to the chassis, the cross-bearers are of minimum depth and are strengthened by central or side Hitch plates. These plates cannot be the fun depth of the bearer throughout its length, because clearance must be provided for the inner longifudinals of the bottom frame if they be continuous. It is a good plan, therefore, to turn the Hitch plate at this joint, so that the end _ may be bolted through the longi tudinal.

Corner plates are useful for reinforcing the framework in many places, such as the joints between the waist rail and pillars, and the junction of the bulkheads with the side framework. The bulkhead is also stiffened by means of a waist plate with cross-bracing below..

The lower corner brackets, or gusset plates, which secure the cross-bearers to the pillars are made in one piece with the bearer Hitch plate, or they are designed for bolting or welding to them. As the pillar is extended below the top of

the chassis, there may be gussets both above and below the floor, whilst, with a half-drop window, the pillar may be plated to the bottom of the outer or inner waist rail.

The upper gusset plates, which strengthen the joint between the pillars and hoopsticks of the lower saloon of a double-decker, are similar to those at the bottom and ere useful as a means for attaching the plates at the feet of the pillars of the upper Saloon. By this means, the upper compartment may be built as a unit and afterwards attached to the completed lower deck. These upper corner brackets are also employed for a coach with a sliding roof, to strengthen the sides of the roof opening.

This composite form of construction in which wood predominates gives satisfaction if the timber be well selected and protected from moisture, with all joints strongly made and reinforced where extra strains are imposed. The wood structure may be repaired and new parts made without special tools.

The number of wood parts is reduced by using a metal wheel-arch. This is shaped to bolt to the crossbearers and has flaps to carry the seat rail and any pillar which terminates at the crown of the arch. . A cross-bearer of duralurain is not only lighter than one of ash or oak with a steel flitch plate, but it may be shaped easily to support a sunk gangway. The substitution of metal for wood may be extended to the pillars used in conjunction with wood waist rails, cant-rails and bottom sides.

The 'advantage of metal as a plate, channel, angle or other section is that it is adaptable to all constructional requirements and parts may be bent or shaped to simplify fastening. Even if a metal be liable to corrosion, there are processes available whereby this disadvantage may be remedied.

The all-metal body may be built in a manner similar to that of the composite type, there being bottom, side and roof assemblies. In another instance, transverse units consisting of two pillars, a hoopstick and crossbar are joined by sections of waist rail and other horizontal members, which are bolted between a pair of transverse units.

Another metal constructional unit consists of a side sub-assembly or window and panel frames, the sections being made up into a complete side by bolting them together with an insulating layer between the pillar joints.

The bus body cannot be standardized to the same extent as the private saloon, therefore the metal body, whatever its method of assembly, must be adaptable to different makes and sizes of chassis. The variations possible should also make provision for any modification necessary to make the structure up-to-date in design.

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