Air dams improve aerodynamics
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NTEREST CONTINUES to row in ways of improving the erodynamics of commercial rehicles (chiefly to improve 'uel consumption), and now a orfolk-based company is nanufacturing air dams as well as air deflectors. Norco Franstec Ltd of Britanos -louse, Weston Road, Norwich, offers "Windfoil" air lams ranging in price from £85 xpwards, ex works, excluding VAT. They are designed to fit andemeath the cab in front of the wheels and are attached to the base of the bumper and to the chassis. The shape of the dam reduces air drag underneath the vehicle and is claimed to be equally as effective as a correctly positioned roof-mounted air deflector.
An air intake is cut into the front of the dam to allow cooling air to reach the engine and front brakes; and fitting and removal have been made easy so as not to cause problems for fitters servicing the vehicle.
Zenith Windows Ltd has had a Ford D1411 with a 7.3m (24ft) box body fitted with a "windfoil" roof-mounted deflector and an air dam. Keith Sillingstone, company transport manager, reports an improvement in fuel consumption, after 8000km (5000 miles) over trunk and local routes, from 20 1/km (9.45mpg) to 25 1/km (11.34mpg). An additional benefit noticed by the drivers, he said, was an improvement in vehicle stability, particularly in crosswinds.
Mike Rawlings, technical director of Norco Transtec, stresses the importance of fitting the roof deflector at the correct height and angle — if these are wrong they can in fact have a detrimental effect on fuel consumption.
The optimum height has been found to be at least 70 per cent (but obviously not more than 100 per cent) of the height of the body above the cab roof. A rough and ready guide to whether the angle is right in service is to watch for where a line of dead flies may appear on the bodywork. If this occurs just below the roof line, then it means that the air is being directed just over the roof, reckons Mr Rawlings, and the angle is just about right.
"Windfoil" air deflectors are made from grp and are available in three sizes to cover vehicles ranging in size from 3.5 tonnes gvw to maximumweight tractive units. Cost of the smallest unit is £155 excluding vat.