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CAB COM FORT COUNTS

By John F. Moon

4 s NE must be able to enter it, there must be room

enough for sitting without muscular strain, one must be able to see out of it (forward and back), it must be ventilated, it must be quiet and insulated somehow from the irregularities of the road." The speaker was Mr. V. G. Raviolo, director of engineering, Ford Motor Co. Ltd., and he was referring to passenger cars during an address given to students of the College of Aeronautical and Automobile Engineers, Chelsea, last month. Mr. Raviolo must have realized that if these attributes are essential for a passenger car, in which the average driver spends less than 10 hours per week, they are far more vital in the case of a goods-vehicle cab, in which the driver will spend anything up to seven times that number of hours per week.

The importance of driver accommodation is showing signs of distinct thought by British commercial-vehicle designers and users, and certain cab designs recently placed on the British market have, in some respects, excelled Continental and American cabs. There are, however, far too many cabs still being offered which fall down on such important counts as ease of access, seating accommodation, noise level, heating ventilation, engine accessibility and finish. With the exception of engine accessibility, many of these defects have already been overcome by our Continental and American contemporaries with the result that—throughout the European mainland at any rate—cabs do not rate particularlyhigh in importance when it comes to choice of a Continental vehicle make or type for the simple reason that most of the cabs available are of a fairly high standard. In Britain, on the other hand, buyers are forced to pay far more attention to cabs when compared with the specification of the rest of the chassis, and this in itself is acting as a stimulus to British manufacturers to develop as quickly as they can cabs which will make their products more attractive, both at home and overseas.

It is not difficult to forecast, therefore, that within the next three years some very modern, cabs of widespread appeal will be appearing on the British market. One of the more important points receiving attention lately in various makers' design offices is that of ease of entry, and we can expect to see an increasing number of cabs with entrance steps ahead of the front wheels. This configuration in itself, however, can present subsidiary problems in that a cab of this layout is necessarily farther ahead of the front-axle centreline than a semi-forward-control cab or a forward-control assembly of the traditional type with access over the wheel This leads to high front-axle loadings, which can in turn mean reduced driving-wheel traction which might not be acceptable for off-highway conditions. This

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suggests it would be desirable for one or other of these two types of layout to remain available, but even the largest of our manufacturers will hardly find this feasible from a production angle.

Thus it is probable that improved cab designs could lead to reduced traction in the case of lightand medium-capacity vehicles, though this is a problem which revised tyre designs could overcome.

Notwithstanding possible disadvantages such as this, cab design must be improved. There are several pressing reasons for this, including safety and driver efficiency, but another not inconsiderable aspect is that, as working conditions in other industries improve, operators are going to find it increasingly necessary to have well-cabbed vehicles in order to attract labour—this tendency is most marked already in the U.S.A. and in many Continental countries, whilst drivers in this country have been known to choose a job purely on the grounds of the type of vehicle (and its cab) that they would be obliged to drive.

It is generally accepted that cab design cannot be divorced from chassis layout, but the degree of importance varies between manufacturers, some virtually tailoring their chassis to accommodate the best possible cab, whilst others seem to fix the chassis layout and then leave the cab-design team to do the best they can. Examples of chassis designed to suit cab layout include vehicles with horizontal engines and power units set well back relative to the front wheels. Such configurations undoubtedly can give satisfactory cab conditions, though engine accessibility can suffer. The future could well see considerable. use of V-engines and these could well simplify the provision of good cabs on fairly orthodox chassis by virtue of their relatively small height and length dimensions.

The various aspects of cab design can be divided and subdivided virtually ad infinitum, but the following sections deal

with various cab features—as they are and as they might be. The order in which they appear does not necessarily indicate the order of importance. Nor must it be thought that they apply only to British cabs (some are very good)—and in the same light some of the remarks could apply equally well to a number of. non-British cabs:

SIZE

Some commercial-vehicle cabs currently manufactured tend to be too long and too narrow. The result is that body space is reduced, whilst the accommodation for driver and passenger tends to be cramped, particularly if a wide central engine cowl is employed. Cab length could be reduced in many cases by relatively straightforward repositioning of controls and by making the front profile of the cab almost a vertical straight line: this would permit the steering wheel to be moved forward. and the driving scat and cab rear also. Admittedly, this would result in a very erect driving position, but this is not necessarily a bad thing. The outcome could be a saving in cab length of 12 in. or so.

The main difficulty associated with increasing overall cab width would lie in having to move the driver's controls out from the vehicle centre line also, and this could complicate the chassis construction as it would necessitate outrigging the controls from the side-member much more than at present.

ALL-ROUND VISIBILITY

Most modern British forward-control cabs achieve a high standard of forward vision, and even some of our normalcontrol designs are good in this respect, although it is to be hoped that American styling with very high bonnet lines is never adopted over here. A lot of reliance has been placed on one-piece ,curved wiudscreens to achieve good forward vision and, whilst this objective has been attained, in many cases it could have been done just as well by using flat glass panels: these would, of course, be cheaper and .more simple to replace. Generous depth of glazing in the sides and rear of the cab is needed for really good all-round vision, backed up by large. rigidly supported driving mirrors. Bad-weather -vision can only be achieved satisfactorily if at least 80 per cent of the windscreen area is swept by powerful wipers, and it is high time manufacturers stopped regarding windscreen-washing and demisting equipment as optional items of luxury.

SAFETY

The safety of the cab occupants can never be overlooked, and it is the safety aspect as much as anything else which makes the normal-control vehicle so popular still in many overseas• countries. Obviously to make the cab a " crash-proof " uncrushable shell would be entirely uneconomical, but it is nevertheless not beyond the realms of possibility that this country could adopt a cab-strength test along the lines already enforced in Sweden and which has been causing some headaches to some exporters to that country. Although the head-on collision is the type of accident most liable to cause cab damage and fatal injury to the driver, vehicles do turn over, and cabs shduld be able to withstand crushing in a vertical direction. Nor must the rear of the cab be ignored, for there is the ever present possibility of the shifting load and/or the loose body: The problem is one of providing a safe margin of all-round tab strength without detrimental effect on cab weight, and this becomes more difficult if the cab has deep glazing and thin pillars.

ENTRY

The time is fortunately drawing near when cab entry over the front wheel will b:". a thing of the past. Although ease of access to the cab interior is of prime importance for deliverytype vehicles, it is nevertheless desirable even on long-distance haulage machines; the step-ahead-of-wheel layout is about the best practical solution to this problem for large vehicles, although steps behind the wheel are probably better for delivery vans if the semi-forward-control layout is going to be employed with the object of locating tho engine forward of the line that the driver would take when passing between the kerb and his seat. Several forward-entry cab designs arc spoilt by inadequate provision of grab handles, dangerously small steps and poor door apertures, this latter being due either to bad door shape or insufficient angle of opening. It is not likely that hinged doors will ever be replaced by sliding doors on forward-control cabs that are not integral with van bodywork because of the additional cab length necessary to accommodate the door when it is open.

ENGINE ACCESSIBILITY

Engines become more reliable each year but, nevertheless, good access to the power unit is one of the most important things to be borne in mind by a cab designer. At present there are very few standard layouts--normal-, semi-forwardor forward-control—which offer anything approaching good engine accessibility, and it very much looks as though the tiltcab configuration will be inescapable before very much longer. Already in America 10 of the 15 principal commercial-vehicle manufacturers offer tilt cabs, some companies making as many as three different types of cab to cover their entire ranges.

There is one tilt cab in production in Britain, and this cannot help but be the forerunner of many more designs of this type -on mediumand heavy-duty chassis, at any rate. Not that Britain is lagging behind the Continent in this respect, for the only other tilt cabs made in Europe are of Russian and Swedish origin. Manufacturers are inclined to rule out the lilt cab on the grounds of increased cost, weight and complication, but in many cases the arguments raised have tended to be weak. Admittedly, slight additional cost is likely to be unavoidable, and this would put the first manufacturer to adopt tilt cabs on a large scale at a slight disadvantage compared with his competitors unless he could really " sell " his cab design quickly and successfully. Integral bodywork is ruled out with the tilt cab, of course, but this type of body is primarily used for delivery vehicles, for which the most satisfactory chassis layout is semi-forward-control in any case.

SEATING

Cab seating can hardly be called a science judging by the present state of the art, yet the driving seat can do as much as power-assisted controls to reduce fatigue. In general terms, the comfortable driver is a safe driver (providing he is not lulled to sleep!) and one way of making him comfortable is to provide really comprehensive seat adjustment—vertically, longitudinally, laterally and with squabs and cushions adjustable for angle. Only in this way can the individual physical characteristics of drivers be allowed for, although even then such a seat can be rendered worthless if the relative positioning of foot and hand controls is at fault. Seat suspension systems have received a • certain amount of prominence of late, but their value is purely a matter of personal preference and a seat which can move too much relative to the driver's controls can be a considerable nuisance. For example, sprung seats have been tried on heavy cross-country vehicles, only to have been dropped later in the life of the design because on very rough surfaces drivers found difficulty in keeping their feet on the pedals!

Nevertheless, a well-designed sprung seat which is fully adjustable for the weight of a driver can help to compensate for poor chassis suspension. At all costs, excessive cushion movement as occasioned by a poorly designed spring-case cushion is to be avoided: this type of seat makes driving a most uncomfortable business and can lead to actual physical injury through the driver's back being rubbed up and down the relatively static squab. Foam-rubber cushioning provides a satisfactory and hygienic answer, particularly if combined with a flexible base of textile or rubber webbing.

NOISE

Noise, unfortunately, is beginning to become accepted as a penalty of 20th Century civilization—in all walks of life. Nevertheless, people (including engineers) who have never been inside the cab of a heavy cOmmercial vehicle before are astounded at the noise level inside such a cab. This includes, for example, manufacturers of car-radio equipment! Engine noise is the main problem, but subsidiary noises arise from the road itself, the brakes, the tyres, the body and even the cab assembly. The only logical way of keeping out extraneous noise is to seal the cab completely and to apply soundabsorbing and deadening materials to the cab panels. To do this thoroughly would be unacceptably expensive, but a fairly satisfactory compromise can be obtained by coating the underside of the cab with a suitable material (as already carried out by some of our more progressive manufacturers) and apply similar sprayed coatings to the insides of double E8 skinned areas. Double-skinning in itself has sound insulation properties, in addition to effecting valuable heat insulation.

There is no reason why keeping the noise of the engine out of the cab should be the problem it obviously appears to be— notwithstanding the fact that far too many British diesel engines are on the noisy side. (Not that American and Continental engines are all that much better.. . .) Experiments by at least one vehicle manufacturer have shown that the slightest hole in the panelling surrounding the engine can give a completely disproportionate increase in engine-noise level, so fully effective cowl sealing is vital. Double-skinning of the engine cowl is useful, particularly if a good flow of air can be obtained between the two skins, whilst p.v.c. foam applied over the engine cowl and floorboards helps to reduce the noise level also. Of course, these remarks apply mainly to verticalengined chassis with the engine alongside or ahead of the seats: engines located beneath the floor or beneath the seats do not create the same aural disturbance, which is yet one more (small) argument in favour of a V-engine.

APPEARANCE

The looks of a cab are not usually taken too seriously when a commercial vehicle is being bought, but nevertheless good appearance could sway a customer's choice between one make of vehicle and another if all other things were equal. A vehicle is, after all, a mobile advertisement for its owner, whilst a driver is more likely to take pride and interest in his vehicle if it is something that appeals to his eye. Throughout the world opinions of good looks vary, and it must be virtually impossible to style a cab that would meet with unanimous approval in all its potential markets. Nevertheless,, there is little excuse for " fussy " treatment of the external panelling and the addition of quite superfluous trimming strips and flashes: in the same light the current trend of getting Continental car stylists to design heavy-vehicle cabs is not necessarily the most logical way of going about things.

VENTILATION

The need for adequate ventilation is even felt in our own country at times, and far too few standard cabs are able to provide it. Wind-down windows in the doors are valuable in that they enable the driver to put his head through them when reversing in confined spaces, but the aerodynamics of most cabs are such that very little fresh air enters through them when the vehicle is on the move. The opening windscreen is virtually a thing of the past, except to special order, and even swivelling quarter lights which can be turned to act as scoops look as if they are on the way out. Therefore the driver is becoming more and more reliant upon " built-in " ventilation systems in order to keep cool in hot weather, and current systems leave a lot to be desired. Ideally a cab should be completely sealed, with no opening windows at all, ventilation being provided through an air-conditioning unit so that the air drawn into the cab is cool, clean and dry, but at present such equipment is expensive and heavy (£250 and 200 lb.). The more simple approach is to incorporate cooling ducts in the cab superstructure through which air can be forced by powerful fans so that fresh air is fed into the whole cab, not just to the driver's feet. If the insulation of the engine compartment is effective enough to keep most of the noise out it should also prevent engine heat from penetrating the cab

interior. For extremely hot conditions thc cab needs to be completely double skinned with, if necessary, the addition of a false roof above the main panel and an extensive exterior sun visor.

HEATING.

Cab-interior heating is another subject which causes some anguish to British lorry drivers—and this is by no means the fault of the manufacturers of this type of equipment, who are able to offer heating equipment to meet sub-zero ambient temperatures. The minimum acceptable heater output is 4kW, and in really cold conditions something along the lines of an oil-burning combustion heater is essential, this being ducted to .warm the engine sump, batteries, fuel lines and so forth also. As with ventilation, structural members of the cab can be used to act as heater ducts, and it would be a great help if cab designers could ensure that the passenger's side of the cab obtains some heating effect also. A cab-heating system can be develo.ed quite easily to fill the whole cab with warm air, so th,re is no excuse for fitting meagre heaters which only provi ifeeble jets of hot air iii one particular corner of the

cab. hassis with engines which ruh at low temperatures are at a ig disadvantage and there is at least one well-known engin with which a conventional type of water heater is compl tely useless!

ESE OF C NTROL

It akes sense that any cab layout should offer the best possib e ease of control, yet quite a few do not. In many cases the f It lies not just with the cab itself, the positioning of contr s s—particularly the gearchange and handbrake levers— being ad. The vehicle which is a handful for its driver has bad manceuvrability, irrespective of whether it has a nominally good turning circle, short overall length and so forth, and the cab layout can alleviate this if all the controls are easy to reach and light to operate and the all-round range of vision is good. The actual measurable manceuvrability depends to a large extent on the proportions of the vehicle such as wheelbase, steering lock and front overhang, and cab design—if it is allowed to affect chassis design—can be a deciding factor in this respect. Obviously if the full-forward-control cab is adopted the front axle will tend to be set back, giving a reduction in wheelbase and reduced turning circle: at the same time the front overhang will increase, therefore the swept circle will, if anything, tend to be larger than with a conventional forward-control vehicle. If 16-in. wheels become available for heavier vehicles than at present the question of manceuvrability will present no problems. wheels of this size giving another " cab " advantage in that step and floor heights arc reduced 'by several inches

EASE OF REPAIR

Replacement of damaged parts goes hand-in-hand with simplicity in theist respects, for the more flat panels and sirimle joints that are in a cab, so the morelikely that tab is to get repaired quickly after damage has occurred. Cab materials count for a lot in this respect: steel is the most basic cab material on mass-product:on vehicles, and welding equipment is available in most places that commercial vehicles are to be found. Coachbuilt cabs with timber frames and steel or aluminium panels are relatively easy to repair also, but at the same time this sort of cab isvery often in need of more frequent repair than an all-metal assembly. Plastics are often used on British cabs, sometimes as cladding and sometimes without any supporting framework and, although not a particularly popular material overseas, plastics has the advantage of being resilient (therefore less liable to denting andtearing) and comparatively simple to repair, in addition to having certain insulation properties.

SIMPLICITY

If all the points mentioned so far are to be incorporated in a cab. simplicity sounds as if it will be out of the question, but this is not necessarily the case. One of the most luxurious, practical and well-finished cabs currently made anywhere in the world is of basically very simple construction, with the minimum of curved panels (glass or metal) and the maximum number of common parts throughout its construction—this means. relatively few " handed " items. The 'simple cab does not have to be an ugly cab, nor does it have to be austere. On the other hand a simple, austere and even ugly cab is sometimes desirable, particularly in semi-developed areas in Africa and Asia, and this type of simplicity implies low cost also.

DETAILS

Little things mean a lot, and never was this more true than in the case of a vehicle cab. Whereas I think that such relatively inexpenSive items as coat hooks, sun visors, ashtrays and really adequate stowage for items large and small should be found in cabs of all types, one has to look very hard to find such iternSin certain cabs. Why should a driver be obliged to throw his top coat either in a heap on the fidor, or over the engine cowl (where it probably serves the useful purpose. of cutting out some of the engine noise) when for the modest sum •of 6d. a coat hook could be screwed into the back of the cab? Why should papers, maps and so on be left to fall on to a floor already probably covered in oil as a result of had engine accessibility, when simple pockets can be incorporated in the side and rear panels or on the facia so that these items can be kept together? Why should pedestrians, cyclists and motorcyclists be liable to get hit by burning cigarette ends when at least one ashtray could be provided for a shilling or two'? Why can't the sharp edges of metal panels be folded back so as not to cause cuts and grazes? Why can't wellfitting rubber floor mats be provided as standard? I suggest a few cab designers leave their drawing boards for a day or two and talk to some lorry drivers or, better still, spend a week driving a commercial. vehicle. Then perhaps these questions, and the others, would never ar:sc.