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ANOTHER LOW-LEVEL BUS CHASSIS.
Page 122
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Details of a New Model Clyde with Six-cylindered Engine.
AN INTERESTING new chassis, embodying many improvements, has recently been completed by Mackay and Jardine, Ltd., West Cross Engineering Works, Wishaw, Scotland. This chassis has been built particularly for fast bus work and conforms with most modern practice ; it has a six cylindered power unit and four-wheel brakes actuated through a Dewandre vacuum servo. The pressed-steel frame is quite straight, except for arches over the rear axle, and the units are so arranged that, when fully loaded, there is a straight-line drive from the engine to the underneath worm.
Dealing with the vehicle in detail, the engine has six cylinders of 31 ins. bore and 4-} ins, stroke, cast en bloc with a detachable cylinder head having machined combustion chambers. Cast iron is employed for the pistons, each of which has three main rings and an oil-scraper ring. The valves are sideby-side an enclosed by three covers.
Self centring barreltype springs obviate side thrust on the valve stems ; the spring cup of each is secured by a split wedge gripping a reduced portion of the valve stem. The whole of the engine and gearbox unit is supported at three points?
The oil from the pump is forced to the main bearings and camshaft bearings through a seamless-steel distribut lug pipe cast in the crankcase. Passages are drilled in the crankshaft to supply oil to the main bearings, and even the piston pins are lubricated by pressure through holes drilled in thc connecting rods. Oil from the relief valve feeds the timing gears. A double thrower ring on the crankshaft at the
Lack of the -rear main bearings, together with a special oil-return tube leading to the sump, prevents any leakage into the bell housing.
Carburation is effected by a Zenith vertical instrument and ignition by either the C.A.V. or Delco-Remy coil and distributor system.
A centrifugal pump driven from the fan spindle circulates the cooling water thropgh the jackets and radiator. The last-named has a cast-aluminium header and bottom tank.
A multiple-disc clutch with Raybestos facings riveted to hardened and tempered discs of saw steel takes the drive to a three-speed gearbox, which has central control.
From the gearbox the power is conveyed through a shaft having two large fabric joints to a second short shaft carried in adjustable taper roller bearings 14 ins, apart and mounted on a frame cross-member. The final portion of the propeller shaft is a tube of large diameter with Spicer joints.
Brake drums of large diameter are • provided on all wheels, and the internal-expanding shoes in these are operated through the Dewandre servo. A second set of, shoes in the rear wheels is controlled by a hand brake.
Careful attention has been paid to the suspension. This is, as usual, by semi-elliptics all round, those at the rear being 5 ft. long and those at the front 3 ft. 8 ins, in length.
A steel drop forging is used for the back axle. The worm thrust is taken on a double thrust bearing and the wheels (both at the front and rear) are carried on Timken roller bearings, They are of the detachable steel-disc type with 36-in. by 6-in. S.S. pneumatic tyres—singles at the front and twins at the rear.
The petrol tank, which is of ample capacity and provided with a large filler spout projecting to the near side, is carried outside the frame side member by two pressed-steel brackets.
The main dimensions are :—Overall length, 24 ft. 3 ins.; wheelbase, 16 ft. 6 ins.; track, 5 ft. .“ ins.; dash to rear of frame, 39 ft. 5 ins.; ground clearance up to back axle, 11 ins.
Lighting and starting are effected by a 12-volt C.A.V. outfit.
The chassis is guaranteed for a pertofl of six months or 25,000 miles, whichever is the less, and the price is £730, ex-works.