Leyland Introduc ew 150 b.h.p. Passenger Range
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INCLUDED in the specification of a new Leyland passenger chassis specifically designed for the export market, are a 150 blip. underfloor-mounted oil engine, the Leyland Pneumo-cyclic gearbox needing no clutch pedal, a 9-in-centre worm-driven rear axle, and air-operated braking.
The. new chassis is known as the Royal Tiger Worldmaster and is one of a range introduced to succee.d the Leyland Royal Tiger. The range includes 10 models, being variations of three basic models with wheelbase& of 16 ft'. 3 in., 1,8 ft. and 20 ft for 8-ft.wide bodies measuring 30 ft., 34 ft. and 36 ft. long, The power unit, which develops its maximum of 150 b.h.p. at 2,000 r.p.m., gives a torque of 450 lb.-ft. at 1,100 r.p.m. It has prefinished dryliners, a nitrided crankshaft carried in indiumcoated strip bearings, chromium-flashed Stellite-faced valves and toroidal-cavity pistons.
A by-pass filter of the centrifugal type, in which suspended matter is flung out on to the inside of the bowl, is a new feature on this engine. Shaft or gear drive is employed for all the Gear drive is provided for the water pump, whilst the dynamo and fan are driven at 1.6 times engine speed by shafts extending from a step-up gearbox which, in turn, is driven by a
B6 cushioned propeller shaft extending from the engine crankshaft.
The radiator is carried well forward of the front axle. In connection with the cooling system a large supplenientary water tank is so piped up that even with the radiator blanked off to promote boiling, only steam is emitted, the water being conserved.
A manually controlled exhauster brake is available, the operating lever being mounted: on the change-speed Cat11111% When brought into, action, it releases air which operates two small pistons. simultaneously, one to close the exhaust outlet by a butterfly valve, and the other to cut off the fuel supply.
Attention has been devoted to protecting the engine and other units from dust.. A pipe of large diameter is taken from the front-end of the chassis to the oil-bath air cleaner. Connected to this pipe is a secondary system coupled to the engine, gearbox and rear axle breathers so that only clean air is drawn into these units when they cool down.
Mounted as a unit with the engine is a large hydraulic coupling from which a short shaft takes the drive to the Leyland Pneumo-cyclic gearbox which incorporates a gear-driven oil pump: this ensures adequate lubrication of the moving parts of the unit.
Unlike the preselective type epicyclic gearbox, the Pneumo-cyclic unit requires only two pedals for drivinE purposes—a brake pedal and an accelerator pedal. Gear changes are made by moving a miniature levei through a small gate.
As the lever is moved from one posi thin to another, air is released to one of a number of separate pistons which automatically release the brake band of one train of gears and apply the brake band on another.
From the gearbox, the drive is taken by a short Hardy Spicer coupling to an unusually large worm-driven rear axle which has 9-in. centres. This axle provides for the absorption of high torques as it is computed to have a 40 per cent, longer life with the 150 b.h.p. engine, compared with an 8-in, centre assembly driven by a smaller unit.
The involute-splined axle shafts, which have been produced to a new metallurgical standard, are claimed to have a fatigue life three to four timesgreater than that of shafts previously used.
Tradition Broken
Leyland tradition has been broken by the use of worm and nut steering gear. The air-operated brakes are similar to those used on Tiger Cub models, but have a greater capacity to deal with the higher gross ratings of the Worldmaster range.
A DI valve releases air progressively to the direct-acting brake chambers adjacent to each wheel. These chambers are diaphragm-actuated and operate the brake camshafts through short push-rods and levers.
Incorporated in the levers are Bendix-Westinghouse slack adjusters, brake adjustment being made by turning a miniature worm-drive inside the lever. The snail profile of the brake cams provides for constant progressive movement to the brake shoes irrespective of facing thickness.
Below the brake pedal is an adjustable spring-loaded buffer to provide for normal retardation. If, however, the pedal be depressed to overcome the buffer, such as when a heavy application is made in an emergency, an increased supply of air is passed to the brake chambers_ Brake drums are 15i-in. in diameter, liner width at the front being 5 in. and at the rear 8 in. to give an effective braking area of 702 sq. in. for the foot brake and 432 sq. in. for the hand brake.
A 1,320-w. dynamo is used in the 24-v. electrical system, which includes an electric speedometer incorporating a mileage recorder. The main objects hellind the design of this new range are to provide vehicles that will give a greater margin of performance on heavy service, and at the same time to simplify maintenance and extend the intervals between overhauls.
The vehicle to be exhibited at Earls Court will have the remarkably low frame height of 2 ft. 7 in. This has been achieved by the use of lesscambered semi-elliptic springs and is suitable for vehicle operation only over good level roads. Normal frame height is 2 ft. 10 in., and on both models the front suspension is supplemented by telescopic dampers.
Engine removal for servicing purposes entails little more than disconnecting the two rear swinging links, the front rubber-bushed support unit, a telescopic hydraulic stabilizer and the fore-and-aft location rod, in addition to piping and controls. It is claimed that removal and replacement can be carried out within 30 minutes.
Also to be seen on the Leyland stand will be a more powerful version of the Super Hippo normal-control sixwheeler. This is powered by the blown version of the Leyland 600 oil engine, which now develops 185 b.h.p. at 2,000 r.p.m. The blower is of the centrifugal type, and is mounted between the two branch pipes of the exhaust manifold. Power-assisted steering by means of the Vickers constant-flow hydraulic system is provided. It consists of a ram unit which acts directly on the steering gear, and of a small enginedriven pump and a pressed-steel reservoir. The piston rod of the power ram is pivoted to the frame at its open end and the cylinder barrel, which also houses the control valves, is attached to the drop arm of the cam-and-doubleroller steering.
Easy Maintenance
A ball-jointed rod links_the drop arm to a forward-mounted relay lever and this in turn is connected to the axle steering arm by a short drag link. The small number of fluid connections and the simplicity of the equipment should reduce to a minimum maintenance of the system.
This vehicle will be exhibited with a new double-skinned export cab. The windscreen is moved forward because of the almost vertical steering column, and this has necessitated the addition of quarter lights between the windscreen and the cab 'doors. Fresh-air intakes are also incorporated in the front corner panels.
The rear bogie has identical axles with 9-in, centre overhead-worm drives and fully articulated suspension.