Novel Scheme to Improve Bus-body Building
Page 29
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AMONG the several advantages claimed for a new form of doubledecker construction, which has been designed by the Bristol Tramways and Carriage Co., Ltd., Trarnways Centre, Bristol, are great strength, combined with low weight, ease of manufacture, and the provision of more headroom and wider seating space than are usually possible.
Furthermore, the system eliminates the need for a separate chassis frame— in the commonly understood sense—as the engine, gearbox, and axles can be attached direct to the structure by suitable means. Nevertheless, the actual design is primarily for a body frame which can be mounted on a normal chassis if preferred.
The side frames are built up of superimposed rows of pressed sheetmetal sections, each 'section (1) in the lower row and (2) in the second row being of cruciform shape, and those (3) in the top row being T-shaped. All horizontal and vertical arms are jointed where they meet those of the next section. In this manner two rows of window openings are provided.
In line with the vertical arms are positioned the cross-members of the structure. These are made on a similar principle, and each comprises a lower U-shaped sheet-metal section (4), an H-member (5) formed, from two Tpieces and. an inverted U-shaped section (6), also built-up from two members.
Joints under shear-stress are flexibly united, whilst those taking other loads are connected rigidly by welding or riveting. A feature of the lower trans
verse section is that its bottom part is in the form of a lattice girder.
Mild steel, alloy steel, and light alloy are all named in the patent specification relating to the design (No. 549,220), which, in addition to that of the Bristol ,company, also bears the name of A. J. Romer, as suitable metals for the construction of the various frame members, and it is pointed . out that the use of these
" cantilever " sections lends itself to the manufacture of Convenientlysized sub-assemblies, which may be produced separately. All similar sections are interchangeable and the sub-assemblies would be erected on a jig.
A further noteworthy point is that the cantilevers, at their points of interconnection, may be reduced to small dimensions, thus permitting the least encroachment upon passenger space.
When the vehicle is built without an independent chassis, longitudinal frame members are used, which may pass through apertures in the lattice girders or may be formed in short lengths secured to the cross-bracing frames.