Too Much Power to Their Elbows
Page 33
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MUCH can be learned about current vehicle designs by eavesdropping on conversations between drivers in cafés. By doing so, designers in particular would obtain a far better insight into the success or otherwise of their products than any amount of " official " market research could provide.
For instance, they would discover that power steering is not regarded by all drivers in the light that manufacturers' sales and publicity departments cast upon it. They might hear discussed a make of vehicle which has power steering as standard. The reason for this apparent refinement is that, because of the design of the steering, the vehicle is extremely hard to drive without the aid of power. Any driver of this type of lorry who has had to be towed with a dead engine will testify to the difficulty of turning corners.
If such a vehicle were being driven along a winding road at more than 30 m.p.h. and the steering power suddenly failed, the driver would be fortunate if he could apply sufficient effort in time to negotiate the next bend. This would suggest that, ideally, all normal road vehicles, whatever their size, should be designed to be completely controllable without any form of steering servo.
Such equipment could then be offered as an aid to general ease of control, particularly at low speeds. A servo is of special value when, for instance, a large vehicle has to be turned around in a relatively small yard, as it enables full lock to be gained far more quickly than would be possible without power assistance. ' Cut-out for Safety?
The " deadness " of certain power steering systems on icy or greasy roads is regarded by some drivers as a great source of danger. In particular, they fear the risk of being unable to correct a skid, purely because of the lack of " feel " at the steering wheel. To meet such conditions it might be advisable to incorporate some form of cut-out in the power system, so that the driver could have purely manual steering when road conditions seemed to demand more positive control.
An analogy is to be found in braking systems, particularly those air-pressure layouts in which the pedal consists of a small treadle with an extremely short range of movement. It is difficult enough to obtain braking control with such a pedal when a vehicle is empty and running over smooth roads, but, as perfect surfaces are rare, either excessive or inadequate pressure is likely to be applied with such a sysLem in making a normal stop. Estimation of safe stopping distance thus becomes a lottery.
Drivers are not noted for having either bigger or smaller feet than any other class of human being. A large, heavy vehicle demands a sensibly sized brake pedal with a reasonable degree of travel. It is important that the driver should be able to apply the brakes by " feel " without having to be so feather-footed that he is almost afraid to touch the pedal at all.
Brake-pedal Improvement Many vehicle manufacturers are already aware of the shortcomings of this type of pedal, which originated in America. They are retaining the kind of brake valve normally associated with it, but are providing a proper pedal. In this way, the driver is given a chance to apply the brakes smoothly and thus overcome one of the possible disadvantages of an air-pressure system, in that brake reaction often tends to be harsh unless it can be properly controlled.
The reverse can be said about many hand-brake layouts, particularly on vehicles in the 5-ton to 8-ton category. Although many people are loath to accept the hand system as anything but a parking brake, it can --properly designed—provide a useful emergency brake and some can give as much as 50 per cent. of the retardation provided by the foot brake.
The important thing about a hand-brake system is that the lever should be easy to apply to its fullest effect. This means that the lever should be placed within easy reach of the driver—without being so close to other items in the cab as to cause the risk of grazed knuckles— and so shaped that the maximum leverage is being exerted just as the brake facings touch the drum.
Already the winter is with us and roads in Scotland have been dangerously slippery several times this month. One of the ways of preventing accidents on such surfaces is to give drivers vehicles which instil confidence because of their controllability. There is danger in reducing physical effort to such an extent that drivers become afraid of their choices.