New Dennis 5-litre Oil Engine
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ANEW power unit to be introduced at the Commercial Motor Show will be the Dennis 5.06-litre oil engine, the first small oil engine to be made by Dennis Bros., Ltd., Guildford. The engine will be shown fitted to the Centaur 7-tonner, although it will be available for, other models of the Dennis range.
With a 98 mm. bore and 112 mm.
stroke. this . six-cylindered . direct injection unit develops 42 b.h.p. at 1,000 r.p.m. and 75 b.h.p. at 2.000 r.p.m. Its cylinder block and crankcase form a one-piece iron-alloy casting, fitted with wet cylinder liners of nickel-chrome cast iron.
The practice of designing the main casting so that it may be turned end for end has been followed, and the component parts may be mounted on either side of the unit, according tb requirements. Even the flywheel housing. which is bolted to the crankcase. is
designed and machined to carry the starter motor on the left or right-hand side.
Notably robust, the seven-bearing crankshaft has main journals of 31-in. diameter, and wide, 21-in. diameter crankpins. Because of the unusually large crankpins, the connecting rods have been split obliquely at 45 degrees
to permit withdrawal of the rods. through the cylinder bores.
The pistons, of silicon-aluminium alloy, are anodized to provide good wearing qualities. Each is fitted with three wedge-section compression rings and two scraper rings, one above and one below the fully floating gudgeon pin. SpIring circlips retain the gudgeon pin in position. Combustion chambers are formed in the piston crowns.
Twin cylinder heads, housing the valves. are fitted, each covering three bores. The valves are disposed approximately on the centre line of the cylinder bore and the injectors are set at an angle to direct the fuel flow into An Eaton-pattern oil pump is mounted on the rear main-bearing cap, delivering lubricant through a highpressure filter to the hollow camshaft and then to the main and big-end hearings. An intermittent full-pressure oil feed is provided for the rocker gear. 'whilst the pistons and small-ends are lubricated by splash-feed.
.An interesting feature of the lubrication system is a drilling in the top of the connecting rods to form an oil reservoir. This provides an immediate supply of oil when the engine is first turned.
Tandem Mounting
A centrifugal-pattern water pump is Mounted in tandem with the fan in the front of the cylinder block and, driven from the crankshaft by a V-belt and pulleys. Cooling water is fed to drilled gallery pipes bolted on the sides of the cylinder heads, directing water past the injector sheaths and circulating it round the valve seats. A thermostat may be fitted if required.
The dynamo is driven in common with the water-pump belt drive, provision being made to accommodate a unit up to 7 ins, in diameter. The 24-volt starter motor drives a detachable :ing on the flywheel.
C.A.V. fuel-injection equipment is provided. the fuel-injection pump being pneumatically governed. Fuel is arranged to be fed to the injection pump by Autovac or pump supply.