Driver comfort is itie business sense
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aham Montgomerie reports the latest thinking from the I MechE conference
OD DRIVER environment acts business economics ce a driver who is fond of truck utilises it more onally. This was the claim de by Leif Strand, product fining manager of the Ivo truck division when taking at the conference lanised by the Institution Mechanical Engineers ened Function versus learance in vehicle den.
kccording to Mr Strand, rational reliability, quality I driver environment are the si essential aims in Volvo's relopment work Because erent areas of transport make erent demands on the enmment, the main requirents for a good driver-eninment change in priority.
or example, said Mr Strand, al distribution vehicles uire easy entry and exit for driver, whereas with the g haul type of operation vo gives a higher priority to a nfortable driving position I good travelling comfort.
n relating the different dends of drivers for different s, Mr Strand quoted some interesting statistics from Volvo field studies. For example a local delivery driver gets in and out of his vehicle 30 to 50 times a day. For a tipper driver, the figure is around 20, with the equivalent for a long-distance driver being 10 to 15 times. At the top end of the scale, Mr Strand said that Volvo has recorded a peak value of 180 for refuse collection vehicles.
Thus Volvo requires that the steps into the cab must both: function as foot scrapers and prevent slipping; and be equipped with an edge protection to prevent the foot from slipping off the step. There must also be well placed grab handles to simplify climbing in and out.
Tiring noise
Mr Strand emphasised that noise is a major factor in causing a driver to tire and lose concentration. He mentioned that an investigation carried out by the Swedish Drivers' Association showed that half the vehicles investigated caused a deterioration of hearing after 61/2 hours. The recommended maximum interior noise level is 7 6dBA 'according to the ISO standard and this, claimed Mr Strand, is the level achieved in the current F10/F12 Volvo range.
The main source of noise inside the cab, said Mr Strand, is the engine, together with certain related components such as the cooling fan and the fuel pump. He admitted that noise -damping is a difficult technical problem to solve.
Volvo has incorporated heavy sound-insulating floor mats and damping material on the cab walls, while at the same time all the .holes in the floor which could act as noise sources have been eliminated save one. This is for the gear lever which is sealed via an insulated bellows. arrangement and a two-piece gear lever which is joined together via a vibrationeliminating rubber layer.
According to Mr Strand, the more miles covered each year by a truck, the greater the running costs for such items as fuel, tyres and brake linings. This .means that the driver's skill and the care he takes of his vehicle become more important the longer it runs. Volvo estimates put the running costs for a UK long-distance truck at approximately 45 per cent of the total costs.
Thus for economical reasons, said Mr Strand. it is extremely important that the driver takes good care of his truck.
Wind resistance In his paper entitled Common and distinguishing factors in the development of light and heavy trucks Dipl-Ing Artur Mischke of Daimler-Benz said that the correlation between function and appearance in commercial vehicles varies with the different weight categories. Daimler-Benz has found it 'convenient to divide these vehicles into two categories: light vehicles used mainly for local delivery purposes and heavy trucks — including the medium heavies — used primarily for medium and long-distance transport.
It is obvious, said Mr Mischke, that wind resistance which has a remarkable influence' on the external appearance of the vehicle, has a different value in the case of the smaller vehicle than with the large. This difference, as a func tion of vehicle category, can also apply to the engine, where the high power output of the heavyweight machine requires a different body design on account of the larger ergine size to that of the lower-powered vans.
However, it is also easy, said Mr Mischke, to find examples where there is no definite relationship between function and appearance, on the one hand, and vehicle size on the other. He cited most parts of the drive line, suspension systems and shock absorber units which are less affected by the problem of function/appearance — although they do depend upon vehicle size.
Mr Mischke went on to discuss several examples of the partly opposing relationships between function, appearance and size, including the influence of wind resistance. He maintained that an aerodynamically favourable body design is important for vehicles used mainly for long distance transport.
For example, the wind resistance of a 38-ton drawbar combination at 80km /h (50mph) on level ground accounts for about 35 per cent of its fuel consumption. Because of the operational conditions, long haul machines must have streamlined cabs — even if this meant higher manufacturing costs, said Mr Mischke.
On the other hand, small vehicles cover less mileage per year at speeds so low that a reduction in drag makes no improvement to fuel economy.
Another example quoted by Mr Mischke was that of the chassis frame. Because the chassis manufacturer is not always able to influence the bodybuilder of the local delivery vehicle, the chassis frame itself must have sufficient torsional rigidity to protect the body from excessive stress.
The result is a torsionally rigid frame with box-type longitudinal members. In contrast to this, ladder frames with
open-section longitudinal members are typical of the heavy lorry as it fulfils the requirement for maximum versatility.
The difference between road transport operation in Europe and in the USA was highlighted by N. B. Chew of the Freightliner Corporation. In his paper Special customer demands Mr Chew claimed that the American operator has a strong influence on the choice of components and the configuration of the chassis he buys.
Across the Atlantic, said Mr Chew, the manufacturer controls the design of the vehicle and the components that go into it up to and including the Class 6 category. These components are manufactured by him or to his specifications and he carries the warranty on all the parts.
However with the Class 8 machine — by which the Americans means 33,000lb gvw and above (15 tonnes plus) — the major components are almost always made by outside companies. These outside companies do the development work and carry design and manufacturing responsibility, said Mr Chew.
Complete freedom
. "Can the operator be given complete freedom to customize his own vehicle for his particular operation?" asked Mr Chew. He maintained that the answer was "yes" within certain constraints. These restrictions include the legislation which formulates the basic design, for example the overall length, width and height. Then, said Mr Chew, there is the constraint of .what components are available for the vehicle's construction.
The economic feasibility of adapting a vehicle to specific requirement for a justifiable cost was a further constraint which could not be ignored. He went on to say that the US manufacturers have structured themselves to handle this question by focusing on one significant segment of the market — from a fixed model builder at one end_ to the flexible custom builder at the oth,..r.
According to Mr Chew, Freightliner typifies the extreme in US custom manufacturing, which generally requires more engineering hours per vehicle• than that of the factories with more rigid specifications. "What about the extra cost for this degree of specialisation?" said Mr Chew. He argued that when you consider the driver's wages for five years, the cost of fuel, tyres, maintenance, licences, taxes and the cost of money, then the cost of the truck is only about seven per cent of the total financial commitment to operate a Class 8 machine. .
In conclusion, Mr Chew highlighted the difference in the evolution of the European truck and its US counterpart. With the former, the vehicle was under the tight control of the desi! engineer and it evolved with great emphasis on ride al human comforts.
In contrast to this Mr Ch( explained that, under the i fluence of the operator, the 1 vehicle had .evolved with higher emphasis on durabili
reliability and ioa carrying capacity—with hurr factors lower down on the list priorities. Today's trends E bringing the two apProaclcloser together, with the U. moving towards more driN comfort, said Mr Chew.