The New Renault Diesel Engines T HE high cost of petrol in
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France has for. some time past been cansdesrgners to look around for lessexpensive fuels: It is not surprising, therefore; to find that the development the DieSeI engine is proceeding rapidly in _that country. One of -the latest converts to the Diesel system is the important concern of Renault; which has just put two interesting engines of this type into production, one being a four-cylindered model and tile other :a 4.`six." . . , ..The Renault 41 four" is now incorporated iii a Mon lorry. chassis which has been added to the Renault range of industrial -vehicles for 1930. This 'engine is an airless-injection four-stroke developing 50 b.b.p. at 1,200, r.p.m. The total weight of the engine, With flywheel, is 500 kllogs., and the-bore and stroke are 115 rem. by 180 mm. respectively. Friel is injected by. four reciprooating pumps, the output of which is regulated by a centrifugal governor. The air and exhaust valves, which are
in the cylinder heads, are operated from a single gear-driven camshaft through the medium of push-rods and rockers.
Decompression cocks are provided to allow the engine to be turned over by hand. The substantial chrome-nickelsteel crankshaft is supported in five bearings and the connecting rods are machined from the solid. Aluminium pistons are employed, each piston having five rings.
The fuel is injected into the cylinders at ...a very high pressure through minute orifices which pulverize it into a fine mist of exceedingly small globules. and the complication attaching to the airinjection system, which necessitates a separate air pump, is avoided. The oil fuel is gravity fed to the fuel pumps, and an efficient filter is introduced into the pipework.
Circulation of the cooling water is, effected by centrifugal pump, and particular attention has been given to the design of the detachable cylinder head in the matter of adequate water pas sages. Engine lubrication is on the most up-to-date dry-sump principle, and the maker supplies a special lubricating oil capable of standing up to the very high temperature within the cylinders.
It may be mentioned that the pressure in the cylinder heads rises to 30 kilogs. per square cm. at the moment of injection to raise the temperature of the air sufficiently high to promote com bustion of the fuel. .
As an example of the economy which may be obtained by the use of the Diesel system in France, it may be mentioned that Renault claims a consumption of 20 litres per 100 kiloms. for its 5-ton Diesel-engined lorry. Now, as oil fuel (gas oil) costs only 60 centimes per litre against 2 francs per litre for No. 2 grade motor spirit, the economy becomes obvious. The fivetanner would cost 12 francs only for a 62-mile trip on gas oil, against about 80 francs for a similar journey with a 5-ton petrol lorry using something like double the amount of fuel.