CAN CAB DESIGN BE IMPROVED?
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A Comfortable Driving
Compartment, Combined •
with Good Visibility, are Essentials to Efficiency and Safety By J. Pickles, AFEATURE of many pre-war commercial vehicles was the somewhat spartan accommodation provided for the driver. There are signs that some of the post-war models may show improvemerit in this respect, but there is still much that can be done It is undoubtedly a subject which deserves special attention We repeatedly hear of research being conducted into the working conditions of industrial employees, in an effort to improve. production by raising the standard of their environment. Cleanliness has been shown to increase the workman's pride in his product; to the writer's personal knowledge,, in onelarge factory the floors are cleaned daily, and every encouragement given to eliminate dirt from the equipment. Still further to improve production and the operative's safety, special colours are often used for the machinery and surrounding structure.
Although the commercial-vehicle driver has a valuable vehicle in his care, and his ease of mind at the wheel makes for safety, I do not think that sufficient attention is given to his problems. A motor-vehicle cab should be designed so that there is the least possible risk of accident. Further, it is expected to protect its occupant from the elements, and thus help him to perform his task more efficiently.
Good visibility is important Merely to provide a deep windscreen is insufficient, as good visibility can be obtained from quite a small window area when it is correctly disposed. The most important factor in this respect is the distance of the screen from the driver's eyes; the closer, the better. A close-up windscreen is less fatiguing to the driver in that rain or mud spots do not distract his vision so much, and the field of vision in a vertical direction is also improved. An 18-in. windscreen 3 ft from the driver will provide only a limited forward view, whereas the same depth of screen close up will enable an almost unobstructed forward view to be obtained.
Restricted Vision • With a windscreen having a straight lower edge mounted close to the driver, a good view straight ahead is obtained, but an angular displacement of the eyes, towards the near side,-must result in the field of vision being progressively narrowed towards the near side, as the portion of the screen directly in line with the eyes becomes farther away. A windscreen of this shape is doubly bad, in that not only is the area of forward vision curtailed, but the vital area in the region of the near-side front wheel is largely screened. Indeed, some examples are so bad that a child could stand in the line of travel and not be seen. By curving the lower line of the screen so that it droops towards the sides, much of this otherwise blind area is eliminated.
To obtain the necessary close-up screen, a well-raked steering wheel is necessary, and this should be well up to the driver—a position which, incidentally, finds favour on many vehicles, in that it makes for easy manipulation.
Black Areas
Screen pillars are, in many cases, so located that objects only a little offset from the front area of vision are obscured, and even thin pillars can be annoying if wrongly placed. When the screen is arranged well away from the driver's eyes, and thick pillars used, even a small car may be obscured.
Undoubtedly, the most important single improvement to be made is to position the pillars as far to the rear as possible, and this process is materially assisted by using a "V " screen.
Thick Framing
Cabs of the pressed-steel type are offenders, as the thin-gauge material used necessitates the employment of fairly large sections in order to obtain the required strength. The condition is worsened by the thick window frame of the door, which combines with the windscreen pillar to form a prominent obstruction.
A better method is to use a thinsection channel of heavy-gauge material to serve the purpose of a window frame, the dimensions being such that the channel need be. large enough for only the glass and its anti-draught channel to be housed. In this case the screen pillar can be narrower, as the door-light pillar need not be matched.
With a structure of this type, the doors would, of course, require to be hinged below the waistline, and on one well-known private car in which this form of construction is employed there is a hinge running from the bottom of the door to the waistline.
V " screens, although offering a better screen-pillar position arc, have been fitted with centre pillars of ,undue width; in one example this was 3 ins. wide. This is not permissible on a well-designed cab, and some method must be found of overcoming it. There appear to be at
least two possibilities: to fit two panes of glass with a cemented butt joint in the centre, or a single sheet suitably shaped.
No matter what scheme be employed, the screen must be fully opening and the mechanism for holding it in any desired position designed to avoid obstructing the vision.
Keeping Screen Clear
Assuming that the general driving position and screen arrangements provide a clear view of the road ahead, there arises the question of preventing misting. In spite of the ease with which this can be accomplished, there are many cabs without louvres for directing hot air from the radiator on to the screen. An American cab, recently inspected by the writer, had a driver-controlled shutter installed in the scuttle, which, when opened, admitted fresh air to the cab.
The top of the dash compartment on one side, and a deflector on the , other, were so positioned that a part of this air was directed towards louvres in the lower-screen surround. This partial opening of the ventilator enabled air to be directed on to the windscreen.
Bright sunlight is another factor to be dealt with, as it not only reduces visibility, but causes serious strain on the driver's eyes. The provision of a suitable glare shield is, therefore, a necessity. There is a satisfactory plastic shield which, having a universaltype of mounting, may be arranged in any required position.
Some of the American commercial vehicles, seemingly designed with the intention of impressing the operator's wife rather than for utility, have sharp, V-type windscreens. An ornate instrument panel joins the two screen pillars, and a large and highly finished panel links the dash to the screen framework.
When the sun shines the rays impinge on the panel and are reflected into the driver's eyes. If this piece of metal is to be used, it should either have a matt finish or be covered in dull leather cloth.
Unwanted Ornamentation Chromium-plated ornaments on the radiator grille and on the bonnet top are also offenders in this respect. This applies to many American vehicles and some British models. One wonders whether perpetrators of ornate cabs realize that a strictly functional vehicle. may also be attractive in appearance, .as, for example, A.E.C. and Leyland, to mention but two. On the . other hand, we have quite a few expensively "styled" efforts which-, the designers appear to think require even more embellishment in the' form of offensive ornamentation.
Side-window operation is effected in several ways. Winding apparatus, of the conventional car type, is frequently used and, as a lifting gear, works efficiently. The operation is, however, invariably a littleheavy, and several turns are required to effect the desired result.
To drop the window needs an excessive amount of time, and although satisfactory for the passengers' side, is not suitable for opera
tion by the driver. There are also the disadvantages that the door thickness requires to be somewhat increased, -Ind the initial cost is greater than with other systems Half-windows, sliding horizontally, are often used, and these undoubtedly possess the virtue of rapid opening. They have, however, the disadvantage that only half the window opening is available fog the driver's head when he is reversing with a closed door Simple Window Operation In my opinion, the best method of window opening is that in which the window may be lifted or dropped with the aid of a simple handle cemented to the window A small trigger in the interior door panel is used to hold the window in any desired position In the present state of suspension development it is impossible to obtain ideal riding under all conditions of loading, and even when fully laden, ftiffness is more desirable than over-softness. This is a little hard on the driver, who must, Cu many makes of vehicle, be jolted by a continuous barrage of road shocks.
The remedy is, undoubtedly, to .provide a really good seat with soft springs The cost of such a seat need be little greater than that of one with the comfort characteristic of a wood plank Expanded rubber and felt, in combination with rubber, are admirable materials for seat cushions, as they are both hygienic and comfortable.
Seating Design
Before the war, car manufacturers were making a selling point of so-called anatomical seating, which purported to be designed in collaboration with the medical profession with the object of supporting the body to reduce fatigue.
Certain manufacturers conducted serious research in this direction, and a seat based on these principles would be invaluable for commercialvehicle use. The theory is that much of the fatigue of driving can be avoided by building the seat to conform with the shape of the body, thereby supporting vital organs and encouraging correct sitting.
An adjustable seat is a necessity which has often been ignored, despite the fact that a simple arrangement on this principle can be readily provided without undue expense. Not only is it convenient for the driver, but it may well save its cost several times over in the avoidance of minor collisions caused by reduced visibility resulting from too low a seating position Interior fittings of the cab have, in the past, varied from lack of essentials to over-abundance. There was an instance where a maker supplied, what he termed, a cigar lighter. Among the essential amenities is an interior light and a dashlight. The latter, which is universally fitted, is not always satisfactory in that, because of its position, distracting reflections may be caused on the screen.
The alternative is to run with an unilluminated speedometer, and altliough a good driver can estimate with fair accuracy the speed of his vehicle, it is useful to have precise knowledge. It is inconvenient to have to switch on and off to note the oil pressure, especially when the switch is far from accessible. A valuable aid is a rheostat, so that the degree of illumination may be adjusted to suit the individual.
A Dash Locker A locker in the dash is appreciated by all drivers. It can be used to carry food and small commodities. In addition to this, a pocket is useful in which documents may be carried safely and cleanly.
I consider that too little tbought is given to the correct positioning of the instrument panel It is important that the instruments be mounted at such a height as just to miss encroaching on the windscreen area, so that they may be glanced at quickly and with small eye movement. An instrument which is rarely fitted, but which is an invalo. able asset, is a clock. m
There is much for improve ment in the interior treatment of British cabs, and in this respect we can learn a lesson from the Americans. On one American vehicle, for instance, the cab is lined with green-faced cardboard. It is probably not officially described as cardboard, but such it is, and it is so formed and sewn that, after being offered into position, only a few screws are required to secure it in place. It is cheap, but it adds an attractive appearance to the machine and, not being exposed to the weather, is durable.
Synthetic Finishes A method of finishing, at one time projected for the German Volkswagen, consisted of a mixture of adhesive and short animal-fibre. This was to be sprayed on to the metal panel to give the impression of a fabric lining.
[In all the vehicles we have tested since the war we have found the driving compartment to be all a driver could desire. Visibility, in particular, has been found to be of an exceptionally high order.— ED]