New European Design Trends: Small Wheels Catching On
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Big Future for Steel-cord Tyres : Driving Visibility Much Improved : Airspring Progress Slow
GREATLY increased use of steelcord tyres, gaining popularity of 16-in.-diameter wheels, the adoption of lower spring rates, and greatly improved driving visibility Were among the trends foreseen by Mr. John Alden, comMercial vehicle engineer, Vauxhall. Motors, Ltd., in the paPer, "Design Features of European Trucks," which he presented to a meeting of the Society of Automotive Engineers in Detroit,' U.S.A., on Monday.
He set out to give a broad picture of European commercial-vehicle design techniques. psarticularly in so 'far as they compare with equivalent American procedures. He pointed out that, as in America, about half the commercial vehicles sold in Europe were of up to 21 tons gross weight, but European and American vehicles in this category differed greatly in engine power, body capacity and overall size.
U.S. Traffic Growing
Although Great Britain had the world's largest vehicle concentration per mile of road, with America second and Germany third, he believed that America was reaching the same density as in Britain.
Dealing with load ratings, Mr. Alden pointed out that whereas a European 5-ton truck was designed to carry 5 tons, an American truck is usually designed and guaranteed to carry twice its rated payload. A 2-tonner or 21-tonner could safely carry 5 tons without breaking the guarantee—or the chassis.
There had been a tendency in Europe for many years to change from normal to forward control, but the primary object had always been to produce a single design which would combine all the advantages of the varying cab layouts already in use and would have the added advantage of requiring only one basic type of cab. Vauxhall could produce more than 9,000 different varieties of vehicle, although their line of products was built up from only five main engine types, two basic rear-axle and gearbox designs and five front axles.
Lower Bonnets
In 'Europe the engines of normalcontrol vehicles were located lower in the frame than in America, so that the bonnet and wing lines could slope to give good visibility with a deep curved one-piece windscreen. This was contrary to American practice, for stylists tended to raise the bonnet line to produce a massive and powerful-looking frontal appearance. Semi forward control layouts were decreasing in popularity, other than for the lightand medium-weight vans.
The latest trend in cabs had been towards .full forward control, with the entrance ahead of the front wheels. Much of the point of this arrangement was lost by having the engine cowl bisecting the cab, so preventing free access across its
c full width, but certain under-cab engine layouts had been produced with, Mr. Alden thought, the disadvantages of a high frame 'line and Sbmewhat 'difficult engine servicing.
Tilt cabs had been available in Europe for many years, but had not become popular because, he thought, of the additional complication in steering and pedal layouts, in addition to extra weight and cost.
One of the most striking differences between American and European engine types was the far greater use of oil engines in Europe. For vehicles of over 9 tons gross weight the oil engine was generally employed and the additional cost of an engine in a 10-ton-gross chassis could be recovered after approximately 15200 road miles.
Over the past year or so designers had evolved petrol 'engines with long-lire characteristics approaching those of oil engines and modern units could operate for 100,000 miles between overhaul's.
Basic European chassis-frame• design was similar to the American pattern and there had been considerable interest in Europe in welded frames. At least nine manufacturers regularly, used welded construction, mainly in the heavier and more expensive vehicles. Leaf-spring suspension, which was general in Europe for vehicles of up to 21 tons gross weight, would remain popular for many years.
Lower-rate Springs
Independent suspension was employed mostly on buses and where it had been introduced on trucks it had always been accompanied by a weight or cost penalty. Manufacturers were seeking to improve suspension when laden and unladen by adopting springs with lower rates. Bedford had, Mr. Alden claimed, probably led the field with the adoption of longer springs and bigger deflections.
Air suspension was slowly gaining ground in some European countries, but interest in some other countries appeared to have practically ceased. The cost increase inherent in this type of suspension was one reason why it had not proved more popular, and other factors were the continuous riding on the bump stops when big overloads were prevalent and the poor performance of some levelling-valve systems. Air suspension had an important part to play in the future, but a great deal of development work still lay ahead.
Mr. Alden cited the most interesting European trend in wheel and tyre
development as being the move towards smaller Lyre diameters. The lead given last year by Bedford with their lowloading 4-tonner on 16-in.-diameter wheels had hastened the tendency to use such small wheels and tyres, as a result of which the 16-in, wheel would become popular in Europe and perhaps throughout the world.
Steel-cord tyres, such as the Michelin X, gave 60-110 per cent longer life, in addition to being cheaper than conventional rayon tyres. The use of steel-cord tyres was continuously expanding in Europe and it was expected that most manufacturers would soon be making them.
Tubeless tyres had aroused hardly any interest in Europe. Operators had not taken easily to the new size classifications and were suspicious of the overload capacity of such tyres.
Large cost and weight savings were being derived from the use of wheels with discs formed from a square blank welded to the rim, as opposed to the riveting employed when a circular blank was used.
Hypoid Axles
Hypoid gears for rear axles had not gained the same degree of popularity in Europe as they had in U.S.A. One reason was the power loss inherent in the rubbing action of hypoid gearing. Another was the opinion among many operators that a hypoid axle could cost up to a mile per gallon in fuel compared with an equivalent spiral-bevel axle.
The growing Use of dOuble-reduction axles was of outstanding interest. Two-speed axles were becoming more popular now that better tooling and higher production volume ,were bringing down their cost. Nevertheless, Many operators still viewed the two-speed -axle as a coniplicated and expensive_ way of providing high maximum speed for an unladen vehicle and many European makers were providing overdrive gearboxes instead.
Full-air-pressure brake actuation was general in the heavier classes, but the use of air-hydraulic systems was growing. Vacuum or air servos were employed in most vehicles from 41tons gross upwards. Whereas the standard had for some time been to produce 0.5g. deceleration with 150 lb. pedal effort, many current systems decreased the pedal effort to about 100 lb. for the same deceleration.
Limiting Wheel-lock
It was dangerous to decrease the pedal pressure further, because of the risk of excessively fierce braking when unladen. In this connection Mr. Alden cited the Dunlop Maxaret anti-skid device developed for limiting wheel-locking.
Disc brakes trebled the number of stops which could be made without excessive fade and reduced the time needed to change friction material from eight hours to eight minutes compared with a drum brake. The hopes that disc brakes would result in a large decrease in weight did not, however, appear to have been sub
stantiated, but the " squeal problem originally encountered with disc brakes was being rapidly overcome. ,ARGEMENTS which recent years lve shown to be increasingly ary to the Bournemouth bus operated by Hants and Dorset
• Services, Ltd., and Royal Blue ss Services have now been cornand were formally opened last r. The redesigned station cost about 100, and will handle daily 80,000 ;gets and 2,200 vehicle arrivals and ures in the summer holiday season. en the station was originally built 1 the layout was highly unusual, in . was on two levels, with the buses the upper and the coaches the lower The principle has been extended ;old scale.