ANOTHER NEW BRITISH OIL ENGINE
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for light vehicles
A Russell Newberg Three cylindered Road-vehicle Engine, Weighing 10 cwt. and Giving 47 b.h.p. at 2,000 r.p.m.
Original combustion System with Simpler Valve Operation
IT has been known ever since we referred to the R.N. combustion system and engines in The Commercial Motor dated dune 23, 1931, that Russell :Newbery and Co., Altrincham, near Manchester, was working on the production of a high-speed road-transport engine embodying the same system. This engine is now going through its bench tests and has been run at 3,500 r.p.m., although in service it will probably he governed to about 2,000 r.p.tri., at which speed it develops about 47 b.h.p.
In the past week we have observed the engine running at 3,000 r.p.m., as well as at low speeds (220-250 r.P.m.), and its freedom from. vibration and noise gave a good impression. The unit will shortly be road tested, with a view to its adoption, in a cha.ssis of well-known make, for which it has been built.
• R.N. Combustion System Employed.
With the assurance gained by a considerable experience in marine engines, the R.N. combustion system has, without modification, been adopted. We are informed by Russell Newbery and Co. that one of the largest oil-engine concerns In the country, manufacturing engines for stationary and marine purposes, is building engines of up to 200 b.h.p, incorporating the R.N. patent combustien system, which is the subject of llritish Patent No. 361,202, also that, in the agricultural engine field, the system is being utilized under licence, the licensee having already been awarded more than six medals, including that of the Royal Society, obtained in 1932.
An 45-ffset cylindrical pre-combustion chamber, its .axis parallel to the gudgeon pin and its two ends housing the inlet and exhaust valves, is located in the cylinder head, and has a vertical injector in a further offset position.
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The piston crown is conical and has . screwed into it a cylindrical plug of Kayser Ellison heatresisting steel, this nearly fitting the passage or mouth to the pre-combustion chamber. A tangential flat is cut in this circular .communicatine passage so that, as the plug is entering, most of the air remaining above the piston is forced through the two triangular grooves, creating acceleraated Pair streams around the ends of the cylindrical pre-combustion chamber.
The plug begins to enter the passage just as injection, commences, and divides the inrushing air into two streams which, as it were, 'trim the sides of the cone-shaped spray of fuel globules, spinning around the pre-com bustion chamber at tremendous speed and in an orderly manner. This quick and systematic mixing shortens the delay period, so reducing the shock lead on the piston.
As will be seen from an accompanying drawing, the cylinder walls are shielded from the combustion process in its early stage. At top dead centre the clearance above the conical piston crown is about 40-1,000ths in. (when hot), and the small volume of air in this clearance assists combustion.
Good scavenging is claimed, and the feet that the burns gases are swirling • during the exhaust stroke is found to render the exhaust valve less liable to carbonization than is generally the case with a direct exhaust stream. The convex heads of the valves, as will be seen in the drawing, give a waist to the chamber, and this assists the swirl.
Heater plugs are fitted into the preeembustion chambers, not for regular use, but as a safeguard to enable an engine badly out of condition to he started up and driven home. There is a no-compression device to facilitate swinging by hand, but this does not have to be used when the electric starter is employed. The injection timing is controlled by the accelerator pedal.
Whereas in the familiar R.N. engine the horizontal valves are operated from low camshafts by means of push rods and rockers, in the new engine they are operated from high camshafts, just below the cylinder-head joint, through the medium of rockers only.
Dimensions of the New Engine.
The three-eylindered road-transport engine has a. bore of 4i ins, and a stroke of 6 ins., the R.A.C. rating being 21.5 h.p. With a 21-cwt. 18-in. flywheel, C.A.V.-Bosch axial starter, dynamo and bell-housing, but without oil or water, the weight is given as 10 cwt., the overall length being 2 ft. 111 ins., the overall width 1 ft. 11 ins., the height above crankshaft axis 2 ft. 5 ins., and below the axis 11-1. ins.
The piston-swept volume is 80 cubic ins., the maximum torque being 173 lb.ft. at 1,000 r.p.m., at which speed the minimum fuel consumption of .398 lb. per bia.p.-hour is recorded.
The engine will run smoothly at 3,500 r.p.m. lnd, with valve-spring
flutter, at 3,700 r.p.m. It certainly Tuns smoothly at under 250 r.p.m., the only distinguishable sound being the pinks tremble, for Diesel knock is surprisingly absent. Except when accelerating, the exhaust was noticed by us to be practically clear.
Leading Constructional Features.
Turning now to the construction of • the engine, the main body is a light. alloy casting, carrying four recessed, four-bolt main bearings of 3 ins. diameter. Twelve of the ,J6 bolts pass right up through the cast-iron cylinder block, through the base of which they are threaded, and are used to secure the cylinder head. These bolts are not in contact with water. A large doublepurpose Hoffmann ball race is fitted at the front end of the crankshaft. 2
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Midland oil-hardened wet cylinder liners are employed, these having copper rings for the pressure joints at the top and rubber glands at the base of the block, They extend 4 ins, into the crankcase. Eleplex pistons of 1111 53 alloy are fitted, each having four narrow pressure rings and one scraper.
With the big-end bearings freed and the pistons raised, the gudgeorhpin bosses clear by in, the liner tops ; floating pins are used, so the pistons may be withdrawn upward. H-section heat-treated steel connecting rods arc employed, and these have 2i-in. big-end bearings. The valves .are. of Silehrome steel and have split-cone retainers.
The auxiliary chain drive to the C.A.V.-Bosch injection pump and dynamo (the latter acting as tensioner) is at the rear, a second half-speed chain from the injection-pump shaft driving the two camshafts with a tensioner.
The Lubrication System Outlined.
The lubrication system has a geared engine-speed pump, giving pressure feed to the main, big-end, camshaft and rocker-shaft bearings, also a constant supply to the valve stems and a drip feed on to the valve ends. The camshaft, incidentally, has a roller bearing, at the rear, a ball bearing at the front and an intermediate steady. There is a Tecalemit external oil filter.
By means of a cast manifold (carrying a Yokes air filter), the induction air is isolated to prevent more than a whiff of oil vapour from the valverocker chambeT from being drawn into the engine.
Three-point mounting is arranged, there being an ordinary rubber-lined trunnion at the front, whilst at the rear rubber sleeves 5 ins, long and 21 ins. in diameter carry the bearers within recesses in the casting.