Easing the pressure cuts fuel bills
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by our Geneva correspondent
LIGHT-FOOTED and happy 'drivers could cut fuel consumption by up to 10-15 per cent. And this coupled with suggestions to increase vehicle weights could mean a saving of 1,500m litres (330m gallons) per year by commercial vehicles in four European countries.
These findings were revealed at a conference during last week's Geneva Motor Show to operators and vehicle manufacturers from Britain, France, Germany and Italy. They had met to consider the rational use of energy, under the auspices of the IRU.
Dr Sverker Sjastrdrn, vicepresident of engineering and production of Saab Scania, called for a ban on "nervous" driving. He said that drivers could have a significant influence on fuel consumption by driving "peacefully" and without any unnecessary changes in speed, which meant better use of brakes.
He revealed that even with experienced Scania test drivers, a 10 per cent variation in fuel consumption had been achieved using the same vehicle over the same test programme—hut with different drivers.
Before the energy crisis, his company had made a study of energy consumption per trans ported tonne and kilometre.
The accompanying graph shows the result of this investigation, which was based on actual figures for load capacity of registered Scania truck and. trailer combinations. The graph shows that the consumption in kWh per ton-km decreases rapidly with the gvw or gtw.
But the most efficient way to "save it," he said, was by spending money on reducing unladen weight, but not payload; reducing rolling and air resistance; and introducing turbochargers. This would provide a fuel economy of 15 per The conference was told by the IRU that a further 15 per cent saving could then be achieved by revising weight and size regulations to 45 tonnes gvw and 13 tonnes per axle.
When he opened the confer ence, IRU president Mr P. Baragiola told delegates that the results of the study on the use of energy carried out in Europe by the American consultant A. D. Little would be published soon, The results supported the view that energy saving could not be achieved by the restrictive measures practised by many European governments.
The conference considered fuel usage under three headings: How savings can be achieved by increases in weights and dimensions; 0 How vehicle design and construction can assist; fl How training of management and drivers can contribute.
The conference accepted the premise that the maximum permissible gross weight should enable road transport to carry large standardised containers at maximum loading (30.48 tonnes or 30 tons) and that the energy efficiency of a vehicle increased with maximum gross weight.
Proper fuel 'management would show savings; this and the importance of demonstrating economic driving techniques were two factors which the conference agreed were important in the search for fuel economy.
The matter will receive further consideration at the IRU congress in Brussels in May.
Calculations had shown that energy efficiency increased by about one per cent whenever gross weight increased by 1,000kg (19.7cwt).
The IRU claimed that it was thus perfeetly entitled to restate its recommendation to increase the maximum permissible grass weight to 45 tonnes for articulated vehicles and road trains in all EEC countries.
If the axle weight was raised to 13 tonnes, this move, coupled with the 45-tonnegross limit would finally result in savings of at least 15 per cent. This was based on a comparison with a 38-tonnegross and 10-tonne axle system.
Dimensions
When it came to the subject of dimensions, the IRU proposed the adoption of a 16m (52f1 6in) limit for articulated vehicles in order to accommodate one 40ft or two 20ft containers. For solo vehicles, the IRU considered that a 13m (42ft 81n) limit would efficiently improve vehicle loading rates without jeopardising safety.
It was argued at the conference that the race for engine power per hauled ton was no longer justified. The IRU had already demonstrated that a one •bhp/ton increase which provided only a 5km/h (3mph) speed gain on a four per cent gradient, involved an additional fuel consumption of more than five per cent.
Consideration was given to the effects of increasing maximum width from 2.5m (8ft 211n) to 2.6m (81t ein). Delegates took the view that these proposed dimensions would be compatible with the development in palletisation techniques. This matter should receive earnest consideration.
The conference agreed,-however, •that no case could be made to increase the maximum height-4m (13ft In a paper presented by Doctor Sverker Sjostrom, he said that the direct-injection diesel engine had no competition in the economic use of fuel.
Dr Sjostrom went on to say that, although the gas turbine and the Stirling engine had been proposed as possible substitutes for the diesel, substantial developments in the field of ceramics would have to be achieved in order to operate at higher working temperatures. Because further development was constantly being carried out on the diesel engine, the turbine and the Stirling engine were thus "sighting at a moving target."
In order to minimise the fuel consumption, the resistance to motion should be made as low as possible. Dr SjOstrdm said the most important -types of resistance were rolling resistance, gradient resistance, air resistance and inertia. Although rolling resistance was influenced by the type of road, it was also greatly influenced bY the type and condition of the tyres. He said that, depending on the type of operation, savings of five to 10 per cent in fuel consumption had been achieved when using tubeless radial tyres. Tread pattern was also important and tyres designed primarily for off-road transport should not• be used unnecessarily on the highway.
Referring to rolling resistance, Dr Sjostrom said the use of the smallest possible number of axles with respect to the total train weight would give the lowest resistance. A single-drive axle would also give lower resistance than tandem-drive axles.
The conference concluded then, that proper fuel management and economic driving techniques were two factors that will receive further consideration at the IRU congress in Brussels in May.