The Opel 3-ton Lorry Arrives
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Six -cylinder O. H. V. Engine with Downdraught Carburetter; Harmonic Balancer on
Crankshaft.
THE Opel S-ton lorry, which has
' just been introduced to the British market, and of which this is the first description to be published. embodies several features of interest, both in its chassis and drop-sided body. Two models are available, the only essential difference between them being the wheelbase dimension, the short chassis, having a wheelbase of 11 ft. 10 ins., and the longer chassis of 13 ft. 10 ins.
The engine, which is three-point suspended on rubber, has six cylinders with dimensions of 89.9 mm. and 95 mm., the capacity thus being 3.627 litres. Push-rod-operated valves are used, the four-bearing camshaft being driven from the crankshaft by helical gears, that on the camshaft being of fabric Bakelite composition.
Water Jets in Head.
A feature in connection with the exhaust system concerns the special provision made to prevent undue heating, and consequent pitting and distortion, of the inserted valve seats. This is achieved by the use of water jets pressed into the cylinder head, the circulating water passing through them to maintain a continuous spray on to the hottest areas of the head. Incidentally, the water jackets run the full length of the cylinder barrels.
The counterweights of the four-bearing crankshaft are drop-forged integrally with the shaft, and incorporated in the fan driving pulley is an harmonic balancer—features which account largely for the smooth and effortless manner in which the unit runs. Steelbacked white-metalled bearings support the crankshaft, whilst in the case of the big-end bearings the metal is bonded directly to the rods and caps.
The tin-plated aluminium-siliconalloy pistons are each fitted with two compression rings and one scraper, all located above the gudgeon pin, the latter being full-floating with spring-ring location. A gear-type oil pump is responsible for supplying oil to the main bearings, big-ends and small-ends, camshaft bearings and rocker-arm shaft, the vertical shaft which drives both the oil pump and ignition distributor being itself driven from the camshaft by spiral gears.
A downdraught carburetter of the accelerating-pump type supplies the mixture, the petrol pump feeding from an I8-gallon tank located under the driving seat. A thermostatically controlled hot spot is provided on the inlet manifold. A small point worthy of mention is that the petrol feed pipe is brought round in front of the engine, being so located as to receive the direct draught from the cooling fan. The shaft of the centrifugal water pump is combined 'with the fanshaft, and belt driven from the crankshaft.
The electrical equipment is by Bosch, the standard battery being a 6-volt unit of 90 amp.-hour capacity. There is an octane selector on the distributor, which provides for adjustment of the ignition timing to suit the octane rating of the particular fuel used.
A semi-centrifugal single dry-plate clutch transmits the drive to a fivespeed box, providing ratios of 57.01. 35.66, 20.05, 11:69 and 7.40 to 1. An optional axle ratio of 8.41 to 1 can be fitted at an extra cost. The reverse gear ratio, with the standard axle is 54.68 to 1.
Constant-mesh wheels provide for two silent forward speeds with selective gears of the sliding-pinion type for the remainder. Provision is made for a power take-off on the left-hand side of the gearbox.
Open Propeller Shaft.
From the gearbox, the drive is taken by a two-piece open propeller shaft, with a central bearing of the selfaligning double-row ball-type and needle-roller bearing universal joints. The full-floating banjo-type rear axle is fitted with spiral-bevel gears, the housing being a one-piece steel casting.
Suspension is by overslung semielliptic springs both front and rear, all leaves in the front springs being of chrome-vanadium steel, whilst the rear springs are of manganese steel with master leaves of chrome-vanadium.
The hydraulic braking system on all
four wheels is pedal operated, the brake lever controlling shoes in only the rear drums through steel cables. Wheel hubs and brake drums form a one-piece casting in alloy iron, each drum being 151 ins, in diameter with a braking area of 187 sq. ins.
Worm-and-roller steering gear is used, the steering box being located forward of the front axle. The pressedsteel wheels are equipped with 20-in. by 7-in. ta,,res on the front and 20-in, by 71-in. twin tyres at the rear, with six. bolt hub attachment.
The standard body is of the open drop-sided type, mounted on the pressed-steel frame members by a system of channel girders. These girders are arranged both longitudinally and transversely, being bolted respectively to the side and cross-members of the chassis frame.
The method of building up the chass!s frame is interesting, in that the cross-members are suitably pierced and " threaded " on to the side members, being thereafter electrically welded in a jig. This form of construction, whilst lending itself to rapid production, produces a structure of great strength and rigidity.
Points of interest about the body concern the pressed-steel channel-section hinge plates, which run from bottom to top of the sides, the chan
nel-section running around and protecting the top edges of the body, and the easily operated side and tailboard locking devices. The last-named • have a wedging action and can be readily released, irrespective of the load pres
sure, through the agency of an extended lever.
The driver's cab accommodates three men and is provided with Fisher adjustable " no-draught " ventilators, dual screen wipers with remote drive, and
traffic indicators, forming standard equipment,
The Opel short-wheelbase 3-ton chassis sells for £250 and the longwheelbase model for £265. An all-steel three-man cab, with safety glass all round, costs £30, and the respective prices of the two models, complete with cab and drop-sided body, are £310 and £330. The Opel is a product of General Motors, Ltd., 3, St. James's Square, London, S.W.1.