Air Springs for Gay Hostess
Page 64
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QUIPPED with leaf-air front suspen sion; a Leyland Atlantean Gay Hostess double-decker coach has been operated by Ribble Motor Services, Ltd., for over 50,000 miles. Designed by Leyland, and incorporating Dunlop airbelloWs and levelling-valves, the system greatly improves the riding comfort of the vehicle.
Air suspension of the same type will be applied to 25 Atlanteans of the Ribble fleet, of which 22 are now in service on the London, Glasgow, Bristol, and Keswick, routes. The system is particularly beneficial to high-speed running on motorways. .
Although the low, gangway height of the lower deck .created a number of installation difficulties, conversion to leaf-air suspension did not involve any major Modification's to the vehicle frame mernbers. .
Two-cOnvolute bellows of 91-in. diameter, employed on each side, are mounted on cast brackets outriggcd from the main frame member in line with the
standard beam axle. No surge tank is fitted, but surge capacity is provided by cavities in the mounting brackets.
A particularly interesting feature is the use of a torque rod of Leyland design which increases roll resistance and augments the resistance to brake wind-up provided by the leaf-springs. The geometry of the torque rod and leafspring layout, based on the parallelogram principle, obviates stresses in the springshackle and rod bushes when the axle is deflected from its normal position.
The torque rod comprises a tube with solid knuckle ends, which are mounted in Metalastik rubber bushes. At the front, the brackets of the bush casings are welded to the tubular front cross-member of the main frame,while at the rear the casings are attached direct to the beam axle. The rod lies on the centre line of the vehicle and, when acting as a torsion bar, provides equal roll resistance in both directions of roll.
Mounted between the original shackle centres, the leaf springs are designed to eater for the approximate weight of the unladen vehicle without assistance from the air springs.
The only serious teething trouble encountered involved the first leaf springs employed. They had to be replaced by a heavier type to eliminate the possibility of fracture as a result of brake wind-up. Each spring is of the dual-rate type, and the fitting of heavier springs did not change the frequency of the system with the vehicle unladen. Other troubles encountered by the prototype during' 50,000 miles running have been negligible.
Levelling valves are of the latest Dunlop design and are reported to have stood up well to arduous testing and routine running. The valve housings are bolted to brackets attached to the frame Members. They are located in front of the axle on the inside of the leaf springs. ahead of the bump rubbers.