A POWERFUL TRACTOR FOR SEMI-TRAILERS.
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Particulars of a New Berliet Product of Substantial Construction.
ASptCt AT; tractor unit which can be employed with Carrimore or other semi-trailer attachments resembling this type has recently been produced by Messrs. Automobiles M. Berliet, Richmond Bridge Works, Twickenham, London. This tractor embodies a new and very powerful engine having four cylinders, cast in pairs, with a bore and stroke of 110 mm. and 140 ram. respectively. The heads are detachable and the cylinders are bolted down to a cast-iron crankcase. The pistons are also of cast iron. They have three rings and their gudgeon pins are secured to them and -work in bronze bushes in the small-ends.
The crankshaft is a heavy drop-forging with three large bearings. All the valves are located at the near side and are operated through roller-ended tappets working in detachable guides. In order to obtain high efficiency, the combustion chamber is designed to give a good degree of turbulence.
A patent centrifugal governor operating a special butterfly, in the inlet pipe controls the maximum speed of the engine to 1,400 r.p.m. It is arranged in a somewhat unusual manner at the end of a single cross-shaft driven by skew gearing from the camshaft; the other end of the shaft serves to drive the centrifugal water pump, which is accessibly situated at the off side of the engine.
The oil pump, which can be removed from the sump as a unit when cleaning is necessary, supplies the lubricant under pressure through a control valve on the outside of the crankcase to a duct running the length of the crankcase and parallel to the camshaft. From this duet the oil passes to the crankshaft and camshaft bearings' and thence through drilled crank webs to the big-ends. A duet from the front camshaft bearing supplies the single-helical timing gears. Two and a half gallons of oil can be carried in the sump, which has an oil strainer covering the whole area. A three-way cock operated from the off side of the crankcase enables the level to be tested and excess oil drained off or the sump drained entirely.
Ignition is by h.t. magneto with a variable advanee, whilst carburation is attended to by a Berliet instrument.
Cooling is assisted by a large four-bladed fan driven by a flat belt and with eccentric mounting to provide adjustment. The body of the fan forms a large reservoir for oil.
A housing forming a unit with the engine encloses a multiple-disc clutch having Fermi° facings. The housing also forms a support for the change-speed and brake levers. The gearbox is separated from the engine, the drive being taken to it through a short open shaft with two Hardy-type flexible couplings. Three-pointsuspension is utilized for the gearbox, the front end having a large trunnion bearing. The box itself is of cast-iron built up in three sections anl provided with a large inspection cover. It is notable that the upper half, which carries the selector mechanism, can he removed with ease to lay bare all the working parts. The four speeds and reverse give the following ratios :—Top (direct), 9.9 to 1; third, 16.31 to 1; second, 27.93 to 1; first and reverse, 47.72 to 1.
The jaekshaft casing forms a unit with the gearbox, and the differential is driven by bevel gears from the second main shaft, spline(' ends being used on the driving shafts, The large chain wheels are formed solid with the hand-brake drums and bolted to the rear wheels.
Radius rods are provided, and these have stout bronze bushes at the rear ends to carry the axle, whilst each of the forward ends is in the form of a split sleeve carrying a threaded bronze adjusting nut, by which the chain tension can be altered. This is, in turn, connected with the bronze-bushed eye surrounding the jackshaft casing carried on the main chassis frame.
A transmission brake operates on the jackshaft, the drum being keyed on a taper on the near side of the differential housing, which projects from the gearbox. Internal-expanding shoes are operated in large-diameter drums and on the rear wheels by means of a hand lever.
The wheels themselves are of cast steel in cruciform pattern. They are mounted on large-diameter ball bearings and are equipped with solid tyres 950 mm. by 140 mm. at the front and 1,030 tam. by 160 mm. twins at the rear.
The steering gear is of a new pattern with a worm awl a complete wheel, and the crossbar is situated in front of the axle, which has jaw-ended stub axles.
The main chassis dimensions are :—Overall length, 16 ft.: overall width, 6 ft. 9 ins.; wheelbase, 11 ft. 4/ ins. ; frame height (unloaded), 3 ft. 3 ins.; ground clearance, 1 ft. 2 ins.; dash to end of frame, 11 ft. 0/ in. The bare tractor chassis weighs 63 cwt.