Air suspensions
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SEVERAL new types of air suspension will be displayed at the Institute of Road Transport Engineers exhibition at Solihull on May 16 and 17.
By Tim Blakemore
Dunlop will have its new Flexolink semi-trailer suspension on display for the first time, and Mercedes-Benz will exhibit a 7.5 tonne gvw 814 with air suspension on its drive axle.
The new Flexolink is a redesigned, lightweight version of the Dunlop air suspension introduced in 1983.
A weight saving of around 20 per cent has been achieved, largely by dropping a Panhard rod used for lateral location.
Instead, the latest Flexolink has a snugly fitting joint, clamped by U-bolts, between its trailing link, a tapered leaf spring, and the axle beam.
The leaf spring extends to the rear of the axle beam and is cranked inwards to act as a bottom mount for the rolling diaphragm air spring. Brake camshafts can be accommodated at the front or rear of the axle.
Single, tandem and tri-axle bogie versions of the Flexolink, including lifting axles, will be available with individual axle ratings from 7.5 to 11 tonnes. The minimum axle spread allowed for is 1,220mm.
Dunlop is also developing a drive axle version of its new suspension which is likely to become available later this year. Production of the new trailer suspension will begin at Dunlop Engineering's Coventry base next month.
The option of drive axle air suspension has been introduced on the 4.25 and 4.9m (13ft 11in and 16ft 1in) wheelbase, day and sleeper cabbed versions of the Mercedes 814. Mercedes expects its new option to be specified mainly by operators carrying fragile loads, but an air suspended 7.5 tonner is also likely to appeal to demountable-bodied fleet owners and to those operators who require a low platform height.
A constant chassis frame top height of 785mm (31in) is main tamed by the Mercedes air suspension, regardless of load. A manual override control valve, mounted on a nearside chassis outrigger bracket, is fitted as standard and allows the frame height to be adjusted for loading from 706mm to 905mm (28in to 36in) above ground.
Full air brakes are standard equipment on all 814s. The only modification made to the air system of an air suspended model is the addition of two 20litre reservoirs on the nearside of the chassis. Distribution of braking pressure from front to rear is determined by suspension pressure.
The option of air suspension adds 80kg {176 lb) to the 814's kerb weight.