G ive the D river a Better Workshop
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The Ability of a Bus or Coach Driver to Do his Job Efficiently is Largely Affected by the Design of His Cab
By R. A. Mills
ANY conscientious public service vehicle driver will agree that the cab of his bus or coach is his
workshop. His ability to do his job efficiently is largely affected by its design and layout.
Perhaps the most vital consideration is visibility, but in recent years the praiseworthy 'tendency to improve it and to clean up the fronts of buses has been arrested. Bonnets have become higher, wider and somewhat vulgar in appearance. Technically, the new arrangements are superior, in that the bonnet is cantilevered to float clear of the chassis, but the appearance is gaudy.
A neat and sensible bonnet style is that designed by London Transport for its 9T9 Green Line coaches. The nearside wing is formed into a flat shelf joined in a smooth curve with the front bulkhead. Ahead of the wheel it is flush with the front of the radiator and in it are recessed the head light and side light. It looks well, allows excellent vision and is eminently practical.
Judgment of width is a function of
visibility. A good view of the mudguards, the widest parts of the body, is essential.
Width Indication
As the off-side front wing cannot be seen from the cab, the off-side windscreen pillar is usually a guide. Unfortunately, this is often unreliable on modern buses, because the cab is tapered forward of the front bulkhead by as much as 18 in., so that a width indicator is frequently necessary. An external side light visible from the driving seat would form a suitable method of overcoming this difficulty.
Windscreens should be as deep as possible to enable the road to be seen close up to the radiator. Some chassis have peculiarly shaped front dash panels which limit the depth of the windscreen, a most unsatisfactory and untidy arrangement. Single-panel windscreens are valuable because the ugly joint in the glass is eliminated, together with the inevitable draught. Thick pillars are to be avoided.
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Another current fashion is to incline the upper half of the windscreen panel at a sharp angle, so as to reduce reflections from the interior lights. Strangely enough, this is often done in doubledeckers, which have, of course, a bulkhead behind the cab. As there is always a blind behind the bulkhead, this type of windscreen appears to be superfluous, because when the blind is drawn, interior reflections are automatically eliminated.
Drivers are sharply divided in their opinions of the merits or otherwise of the sliding cab door. Its advantages include ease of entrance and exit under close parking conditions, additional ventilation when it is left open, reduced accident risk because the door cannot swing open in traffic, and narrow pillars because of the elimination of binges. The chief objections are draught and rattle.
Emergency Measures .
The flush-fitting sliding door effectively overcomes the objections while retaining the advantages. As far as emergency exits are concerned, the jettison-pattern near-side panel, hinged along its lower edge from, the extreme front of the cab to the bulkhead and with a sliding section opening from the front, is undoubtedly the most efficient. It enables the bulkiest driver to eject himself in a hurry and if the central pillar is avoided, a peculiarly irritating. blind spot is removed. Draught-free ventilation is also provided by this design. A highly commended feature of postwar Dennis chassis is the flat and level cab floor in which there are no wheelarch projections. It is in marked contrast to the type of floor in which the pedals are sunk into a well overshadowed by an enormous wheel-arch, over which the driver has to struggle to reach his seat.
Two of the sources of draught in the cab arc the slots cut in the floor for brake and clutch pedals. Usually, packing is fitted around the pedals, but this never lasts long. On the London Transport RT bus, a footplate through which the pedals project is bolted to the steering column, level With the surrounding floor. The assembly is part of the chassis and moves with it. A rubber sealing strip between the hole and the pedal shafts eliminates draught.
Heating and ventilation have been somewhat neglected. When the driver is seated beside the engine he is usually kept warm, so that a sliding door which can be left open is welcome. In cold weather, however, the average driver closes everything he can and may even pack ventilators with newspaper. This may make the cab warm but the lack of fresh air may have a serious erica on the driver's ability to concentrate.
Positive Ventilation
A more positive means for ventilation is essential and if a heater is fitted to the vehicle itself, the main air supply could be tapped to provide a supply to the cab. An extractor is also essential to ensure constant change of air.
As cold feet are one of the discoriforts with which the driver • has to compete, it is a good idea to provide a suitable rest for the left foot. In its absence, the driver may be inclined to ride the clutch pedal to avoid keeping his foot on the cold steel floor.
Another item which can be criticized in many Vehicles is the driving mirror. Flat mirrors are most unsatisfactory compared with the convex type. Furthermore, the 'mirror must be attached in such a position that it provides a view along the side of the bus, instead, as is often the case with a tapered cab, of a perfect reflection of the cab door. Ease of adjustment is also essential.
In Birmingham Corporation vehicles, the interior mirror, another desirable fitting. is arranged to provide a view of the interior of the vehicle at night when the bulkhead blind is lowered. This is an excellent arrangement.
Particular attention must be paid to the quesi ion of mirrors on vehicles with an entrance ahead of the front wheels. Normally, the near-side mirror does not include in its angle of vision a view of the near-side front wheel. In an underfloor-engined vehicle with an entrance at the front, the inability of thc driver to see the near-side front wheel is a source of danger.
For example, if a would-be passenger runs alongside the bus, he can be seen in the mirror at first, but as soon as he comes abreast of the front wheel he passes out of view. The driver may, therefore, look in his mirror for tardy passengers before moving off and, seeing no one, close the front doors as the passenger reaches the step.
Another danger with vehicles of this type is that passengers on stage services tend to assemble on the platform when approaching q. stop. The driver then finds that his view of the near-side kerb is completely cut off. There were many other causes of complaint in early underfloor-engined buses because no effort was made to provide really -deep windscreens, even though the radiator was eliminated. Examples of what can be done are provided by the Bristol LS coach with bodywork by Eastern Coach Works, Ltd., and by the Burlingham Seagull body.
One of the problems which does not seem to have been solved is that forward visibility at night is seriously impaired by reflections of the interior lights in the windscreen. The expedient of raking the glass to lift reflections above the driver's eye level, is convenient, but a blind behind the driving seat is a much better arrangement.
Although any suggestion on the form of the ideal cab would be simply a matter of opinion, it can be said that generally the arrangement commonly found in underfloor-engined vehicles is not favoured. An improvement on the conventional half-cab would appear to be the most desirable and most acceptable.
Pioneer Approach
The London Transport TF coach of 1939, besides being a pioneer of the underfloor-engine design, represented the right approach towards an ideal
cab. Near-side visibility was exceptional, unequalled as yet by any other design. There seems to be no good reason why the TF cab arrangement should not be used in double-deckers.
Alternatively, it would he difficult to improve on the RT-type cab, which incorporates most of the desirable features which have been mentioned. The RT cab should serve as a guide to other designers and the universal adoption of the RT frontal layout would seem to be preferable to the high, wide and hideous " new-look " fronts now becoming popular.
ln laying out a cab for public service vehicles, the designer should ask himself " how does it work?"—not "how does it look?"