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Advanced design

24th October 1975
Page 39
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Page 39, 24th October 1975 — Advanced design
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Which of the following most accurately describes the problem?

v. reliability by John Darker, AMBIM

Long-life prospects are separate factor when considering vehicle replacement

ROAD TRANSPORT fleet operators devote a good many hours every year to "sounding off" about the shortcomings of vehicle manufacturers. At a recent seminar of work study practitioners it was interesting to listen to the other side of the story.

Mr R, A. H. Aston, manager, Medium Truck Programmes, British Leyland UK, illustrated the close liaison of manufacturers with operators; the operators may not be satisfied with the depth of the manufacturer's interest, or, indeed, his response to suggestions and complaints, but there is no denying that a continual dialogue persists.

Mr Aston illustrated with slides the parameters influencing the concept of the truck in order of priority:

.0 The manufacturer was in business to make a profit; O The vehicle purchaser, probably a member of the allegedly

"permanently impoverished group" of operators, must be able to make a living from its operation;

O The driver, who could spend 75 per cent of his working life in a truck and upon whpm its profitable operation and subsequent replacement so largely depended;

n The public, ever alert to ecological breaches and demanding socially acceptable lorries.

The manufacturer, said Mr Aston, was not thinking of one truck in his design considerations, -but of a whole range of trucks—long-wheelbase haulage vehicle, the tipper, the concrete mixer, the tanker and the articulated vehicle tractor.

Conflicting requirements

Each application presented its own particular requirements and its own design problems. The requirements, some of which were in conflict, needed to be moulded into a range of vehicles assembled from the minimum total number of components as easily and cheaply as the market place allowed.

What factors come into the operator's choice of vehicle? Mr Aston stressed that the whole life cost of a truck was more important than purchase cost— initial down payment—especially with the larger more modern vehicles. 'Downtime, particularly unscheduled downtime, was prohibitively expensive with a maximum weight articulated vehicle. If it could be avoided by the additional cost of a premium vehicle, this extra cost could soon be recovered.

Lack of downtime was a measure of reliability obtainable from two sources, in Mr Aston's view: experience and meticulous attention to detail. The experience came both from the design philosophy and from operational results under a variety of conditions.

"In a way," he said, " advanced design and reliability of operation have conflicting requirements and a truck is immobilised just as effectively if a headlamp switch fails as if a connecting rod comes through the side; both lose revenue, although the repair costs are different."

Engine power option

What is the distinction between durability and reliability? The two should not be confused. "A truck which operates reliably for 150,000 miles or two years but is then worn out is expensive to rework and has a poor resale value. Operators who bought certain vehicles which got off to a very good start found after two years that major components required replacement, that the service cost of these components was very high and that unless they had been replaced the second-hand value of their vehicle was low." No prizes for guessing the answer to that one!

On the requirement for engine power and performance, Mr Aston noted that the operator required just enough power to enable the truck to carry out the necessary tasks for which he bought it.

On the merits of greater power, Mr Aston told a story worth recounting. He became involved in a vehicle under complaint for instability. The operator was carrying a 16-ton load of fairly low density fitting nicely into an artic with a 40ft trailer, 8ft 2in in width and 14ft 3in in overall height. The outfit with •a suitable tractive unit came to about 26 tons and the operator had 'bought a 180hp one for the job.

The journey consisted of a cross-country portion followed by a crossing of the city and finally motorway. The journey and loading cycle could only just be completed within the permitted drivers' hours; hence, during the return trip the driver often found himself hurrying down the country lanes in order to ensure return to base on time.

Mr Aston looked at the vehicle as a whole and decided it was unstable. "But these things are a matter of degree and it was no more unstable than many other vehicles apparently operated successfully by drivers who know what they are about. Anyway, we did what we could for the tractor and while the work was being undertaken we loaned the firm in question a 220hp demonstrator which was the only tractor available at the time."

When it was time to return the 180hp tractive unit the operator stressed that the 220hp tractor was much more stable, although British Leyland knew that the chassis specification of the two vehicles was identical. "In the end it turned out that with the large frontal area the 220hp enabled a slightly higher average speed to be achieved on the motorway sections of the journey and meant that the last part of the trip could be taken at a more leisurely pace."

The moral is clear: when power to weight ratios are selected, "if additional power is merely used to maximise the driver's café break the operator will pay heavily and differences of the order of 5.5 to 9.5 miles per gallon can be measured depending on the experience and enthusiasm of the driver."

While legislation encourages more power, engines are efficient only over a limited torque range,

and torque back-up tends to suffer—a high-torque rise engine will yield a better fuel consumption than an engine with a smaller torque back-up with the same powe .

Ordering spares

Mr Aston touched on the interchangeability of parts in a whole range of vehicles. Those responsible for ordering spares for a mixed fleet of vehicles of a single make may be interested to know that one basic set of parts must cover a 16-ton, 4x2 vehicle, a 6x4 24-ton vehicle, a 4x2 artic tractive unit at 28 and 32 tons and an 8x4 at 30 tons for both haulage and tipping work.

Each of these applications has its own basic requirements which ideally require adjustment to basic dimensions. However, compromise enables the manufacturer to make the range out of one set of basic dimensions and the operator not only gets the advantage of purchase cost, but also reduced inventory improves the availability of both vehicles and spares.

What about ease of maintenance? Here again, Mr Aston was realistic. No designer, he said, is thanked by the operator's maintenance staff for locating that nut and bolt to suit assembly from above when maintenance is actually done from a pit with a body fitted.

Fleet operators who are impatient to see harmonisation in Europe will not be surprised to learn that manufacturers share this desire. What may not be generally known is the formidable amount of paperwork that has to be studied to reconcile the many conflicting requirements. British Leyland's design staff have to know the contents of no less than 24 four-drawer cabinets, not counting a mass of other manuals and documents.

Another matter of joint interest to manufacturer and operator is the risk of legislation, or regulations, affecting a vehicle design either before it reaches the production stage or during its working life. A general point made by Mr Aston concerned the different time scales used by governments and industry. "To a government, short term means as quickly as a Bill can be got through Parliament and long term means six months before re-election. To industry „ • five years is short term and a tooling commitment made today stays a commitment for 15 years and to this may well be added a further five years for the research, development and production phase of a programme, giving a 20-year cycle for major investments during which period a change in fundamental design could be very expensive indeed."

Mr Aston made a predictable plea for some relaxations of the present legal dimensions in the UK as a contribution to improved riding and handling characteristics of maximum length articulated vehicles. "A small relaxation in the overall length limit, whilst maintaining the same load length and monoeuverability parameters, would bring a great benefit in ride and stability and would also ease the difficulty of reducing both internal and external noise levels."

This would seem an appropriate agenda item for the commercial services section of the TGWU. Can manufacturers furnish copper-bottomed evidence of their claims? It would almost be worth while to build a demonstration vehicle to the desired dimensions to prove the point.

To meet noise legislation due to come into force shortly, manufacturers are taking the opportunity to reduce internal noise levels at about the same time. As Mr Aston stressed, these improvements will add to the initial vehicle cost and higher maintenance costs will be an additional cost burden. Perhaps there will be off-setting gains in drivers' general health?

It is sometimes suggested that the hearing of drivers is mar.kedly worse on the side nearest the engine noise. Proof of this —surely an easy matter to monitor—would reinforce trade union pressure for a better working environment.

Among the safety items which could soon become standard, Mr Aston mentioned antilock brakes "approaching the standards required for them to be fitted to every vehicle." Under-run protection, to prevent the kind of nasty situations which so often arise on motorways, may also be featured.

Operators may not welcome extra weight, and marginal increase in maintenance costs, from safety items, but such things are part of the price that must be paid by transport operators for earning a living in an environmentally sensitive world.

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