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Why Was It Designed Like This ?

5th June 1942, Page 31
5th June 1942
Page 31
Page 31, 5th June 1942 — Why Was It Designed Like This ?
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Which of the following most accurately describes the problem?

According to the Writer Designers Are Often Blamed Unfairly for Lack of Accessibility and Other Alleged Faults for Many of Which They. are Not

Really. Responsible

By J. Pickles

AFREQUENT remark of the harassed operator or driver is " Why was it designed like this?" (although sometimes expressed more emphatically), usually followed by a lengthy discourse on what should have been done, and he wonders why design offices are staffed by numskulls and incompetents, who take unholy glee in hiding major components under a mass of equipment and auxiliares.

As a representative of tffis muchmaligned body, I feel that an exposition of the problems entailed may be illuminating to the layman and, perhaps temper his wrath.

A drawing-Office staff is usually divided into sub-sections, each. responsible for a major component, such as the engine, gearbox, axles, frame, etc., and superintended by the chief designer, who is responsible for the efficiency of, the production vehicle. .

• Limitations On Design Through Regulations

The design of any component is influenced by many factors which are not immediately obvious. For instance, the number of regulations laid down by a somewhat shortsighted Government is legion. The first specification is an attempt to obtain maximum. efficiency whilst conforming with these limitations. Components must also be designed; where possible, to be produced by existing machinery and methods.

Many people are of the opinion that, designers are too conservative. It is a fact, however, that even if the manufacturers could be convinced that a new idea would be • advantageous, the buyingpublic would be extremely chary, and, after all, although the manufacturer may be an enthusiast, he makes vehicles to sell. Further, he is always loth to dispense with parts which have been well tried by experience, for obviously it is only by experience that real efficiency and durability can be determined.

Accessibility is always a sore point With operators, but here again the end is often justified. It will be realized that if one type of engine— or other unit—can be standardized for each size, the manufacture will be easier and cheaper, and will reflect favourably on the selling price. Also if an operator uses various control positions for his different duties (such as forward control, side control and normal control, and, if to be exported, the fittings of either rightor left-hand drive), a smaller num ber of spares will be required, as he will be using an engine or other unit common to all chassis.

Sometimes the-conservatism of the operator, in insisting upon a particular body which is in vogue, reacts -unfavourable, on accessibility. The supplier, must obviously produce the type which is in demand. At times, a body will be fitted to a chassis without co-operation with the designer, and more often than not, the bodybuilder has little or no knowledge of the mechanical features, and otherwise accessible components are thus covered through ignorance. The constant search for more body space on an existing chassis does not help matters, for running economy is always the first consideration.

Proprietary articles and electrical components present no little difficulty of successful installation. The former rely for their efficiency and low first cost on quantity production, and the introduction of major alterations would defeat the objects of using them, i.e., low first-cost, proved reliability, etc.

Positions of Electrical Parts Limited

Many electrical parts have their positions limited by inherent conditions. For instance, the cable frorn the battery to the starter-motor must be short to prevent the voltage drop, which increases with length, and the starter-motor itself, of course, is limited to a position radial to the flywheel. The distributor and dynamo must be mounted in positions where they can be driven from crankshaft and 'camshaft, which positions are not always the serviceman's ideal.

A good manufacturer keeps in touch with the operators of his vehicles, and if serVice experience demands additional equipment, the chassis layout cannot be altered to find room for it, so there is no alternative but to make the best of the available space and, not infrequently, at the expense of the accessibility of other components.

Many a vehicle is accused of unsatisfactory -performance when the fault lies in the hands of the operator. Complaints commonly arise through the purchase of a vehicle with an unsuitable rear axle ratio. " After 411, an agent can only •advise as to' a suitable axle, he cannot forbid the sale of an unsuitable one. I have frequently met with operators running semi-trailers with a 3-ton, highgeared chassis—not a brocedure to be recommended.

If by this " hit-and-miss " method, an "A" chassis is suitably geared and a "13" unsuitably, the latter is all wrong and its reputation suffers considerably. A not-infrequent failing of the operator is his unwillingness to pay the little extra for a twospeed axle, which, particularly on a semi-trailer outfit, would make an improvement almost unbelievable to those to whom it is unfamiliar.

Ideal Suspension Hard to Achieve

An ideal suspension .is almost impossible, having to cope, as it does, with loads varying from the weight of only the vehicle to that of the vehicle and load plus' any additional overload a misguided operator may care to put on.

Frequently, inaccessibility is justi fied by the fact that it is better to work once on an inaccessible part than twice on an accessible part. For instance, side valves usually require less attention than do the overhead type, although lacking the ease of adjustment of the latter. Many parts have their positions determined by consideration of operating efficiency, and no matter what goodwill the designer may have, they cannot be moved. ,For example, sparking plugs are placed to give maximum. power and economy; radiator, cooling fan and pump all have locations which are inter-related, and the engine itself must be situated as far forward as possible to give maximum clear frame length.

It is to be hoped that these observations will perhaps bring home to the gear-lever pusher some of the problems of the slide-rule man, and will help to dispel the impression, falsely held by th-e former, that the latter is completely oblivious of the practical problems that are encountered by drivers and maintenance engineers.

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