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No "Leaning" in Trailers with Air Suspension

21st June 1957, Page 53
21st June 1957
Page 53
Page 53, 21st June 1957 — No "Leaning" in Trailers with Air Suspension
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THE manner in which the Dyson

Aeroride Haulmaster semi-trailer provides a self-trimming action was demonstrated at Liverpool last week, writes a representative of The Ccimmercial Motor. By observation on the vehicle itself, and from a following car, it Was seen how the system automatically adjusts itself to the load being carried, or to the absence of load.

It keeps the platform on an even keel even if various consignments are itl distributed,

On the cant of a steeply cambered road, the automatic adjustment prevents the trailer from "leaning," although the method of control is such tha t the normal balancing reactions occur while cornering. In the case of a rear bogie standing on a steeply sloping surface. the platform is stabilized parallel to the centre line between the two axles.

Ample Articulation

The design permits a variation of height of at least 6 in. between the two axles if the vehicle is on rough ground. An example of tie effectiveness of the system was given as concrete ballast blocks were unloaded. As each block was removed by the travelling crane the platform momentarily lifted but within seconds settled to the original level. The only platform height change from full to unladen was the negligible variation accounted for by tyre deflection.

Throughout the running test it was possible to sit, without any discomfort whatsoever, on wooden seats at the rear of the semi-trailer. When emergency braking stops were simulated, . the vehicle pulled up quickly, the locking of the rear wheels being achieved with the bogie square-on and without any trace of "dance."

The trailer ran smoothly whether loaded to capacity or unladen, the " riding " when unladen being particu larly impressive. '

It has been designed for the carriage of maximum capacity payloads of 16-17 tons at 30 m.p.h. and is intended for use with any tractor of the appropriate class with two-line air braking.

The prototype is 25 ft. long and 7 ft. 6 in. wide, but semi-trailers will. of course, be built to customers' required dimensions. Lightweight tubular axles of the tandem bogie carry axle connecting beams that are integral with the air compression chambers.

Above the chambers on each side are the double air bags that provide the air suspension. These bags are manufactured in this country under licence by the Andre Rubber Co., Ltd., who also made and supplied other rubber components incorporated in the suspension. The bags are constructed from fabric and rubber in the manner of a tubeless Lyre. They are neoprene covered to provide resistance to oil, petrol and similar substances.

They are connected to the compression chambers by means of airtight joints and are fitted with internal rubber stops so that the vehicle will not be put out of action in the unlikely event Of failure of the air supply.

The air supply comes from the air braking system by way of a valve to the suspension reservoir. This valve ensures that the braking is isolated in the event of any failure of the air suspension. Air is fed through to the compression chamber by way of the height control valves. These valves automatically control the pressure in the air bags with the result that a constant static height is maintained. Pressure in the bags varies from about 5 lb., with the semi-trailer unladen. to 45 lb. when fully loaded. If overloaded, the valves automatically increase the pressure and so maintain the platform height. This automatic adjustment permits the clearance allowed over the top of the tyres to be reduced.

A torque arm is fitted to each axle, located' in a large rubber bush mounted in a frame suspended from the chassis cross-members. By this means, both braking torque and side thrust are accommodated. Rebound limiting rods are provided between the compression chamber and the chassis frame, and double-acting Armstrong hydraulic shock absorbers are also employed.

There are no parts in the suspension that require lubrication. The manufacturers state that the air suspension bogie is a little lighter than its counterpart on laminated steel springs so that there is an initial saving in tare weight. They suggest that'the better "ride." may give an opportunity for additional reductions in respect of body, weight.

The air suspension system is that developed by, the General Tire and Rubber Co. in the United States, and the bogies have been built by R. A. Dyson and Co., Ltd., on the basis of U.S. practice, -but engineered, to suit conditions in Britain and elsewhere:

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Organisations: US Federal Reserve
Locations: Liverpool

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