dulti-fuel Unit Capable of 5,000 r.p.m.
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.460 c.c. Unit Gives 17.5 b.h.p. on Variety of Fuels : 70 b.h.p. Engine Envisaged HE Elstree Series 460 c.c. compression-ignition engine, a new unit tnufactured by S. E. Opperman, Ltd.. reham Wood, Herts, will consume oil petrol, paraffin or tractor vaporiz: oil with equanimity but without idification, and will run at up to 5,000
.m. in vehicle applications. Ii is an -cooled single-cylindered unit with a re of 3 in. and a stroke of 5 in., weigh: only 60 lb. bare or 90 lb. when fully lipped for use in vehicles.
The engine can operate at speeds of tm 350-5,000 r.p.m.. producing 17.5 t.p. at the higher figure. For industrial t, it is limited to 3,500 r.p.m,.. at which :ed it develops 12 b.h.p. Maximum que occurs at 3,400 r.p.m.. although : torque curve is comparatively flat. ese ratings are for operation on oil 1, but there is said to be little power s when other fuels are used.
Dutwardly the engine is similar to eonitional small air-cooled industrial rd l units, but differs markedly in conaction from them in order, to cope h the higher firing and working preses involved. The maximum B.M.E.P. ire is 105 p.s.i. at just over 3,000 .m. and the standard compression ratio to 1.
2ast iron is used for the cylinder barrel I head. Overhead valves are situated a-by-side on the transverse centre line the engine. The inlet port is 1 in. in meter whilst the exhaust-port diameter 1* in. Long pushrods actuate the ves through rockers from a camshaft ated in the crankcase.
Circular Cavities
Ile Bryce Berger pintle-type injector ocated at the rear of the cylinder head the top of a throat leading from the -topped combustion chamber. Circular :ides are cut in the piston to allow for valve opening, but the piston crown otherwise flat_ It is this apparently 'pie combustion chamber design which es the Elstree engine its omnivorous ,racteristics, and provides good cold rting on all fuels. No heater or other rting aid is provided or thought :essary.
k, 1-in, diameter gudgeon pin attaches piston to a sturdy, forged-steel meeting rod. This is of normal tction and is I in. across at its widest nt. The split big end contains a plain )sphor-bronze bearing. A forged-steel nkshaft is used and this has a 2+-in. meter crankpin and two main journals the same size, all the bearing surfaces ng case-hardened.
he main bearings are also plain )sphor-bronze ring-type components. I their caps are secured by bolts which s upwards through the crankcase to I flush with the surface on which the ply spigoted cylinder barrel is located. ..:11 bolt is tapped to take a long stud, cylinder barrel and head being bolted vn on to these. Thus the main work
ing stresses are contained, in effect. by through-bolts passing from the main bearing caps to the top of the cylinder head.
Cast aluminium is used for the onepiece crankcase to which is bolted a sump of similar construction which holds 4+ pt. of oil. A gear train from the crankshaft drives the valve camshaft, which incorporates a third earn to operate the Bryce-Berger jerk-type injection pump, mounted at tho rear of the engine.
This pump has no governor, engine performance and speed being regulated by a normal rack and initial setting of pump output. At present the pump plunger is not positively lubricated and. for operation on parallin and petrol, oil has to be added to the fuel. The pump will, however, be modified to make this unnecessary.
Engine lubrication is effected by a submerged gear-type pump feeding the mainand big-end bearings through drillings in the crankshaft. The small end and cylinder walls are oiled by splash and the valve rocker box receives oil vapour from the crankcase. Thus there is no external or internal oil piping.
The engine, which costs £105 in its basic form, has already been fitted in small industrial tractors and in the prototype of a lightweight four-wheeled car weighing 1,100 lb. In the car, operating at up to 5,000 r.p.m.. it has completed 2,800 hr., running on various fuels without the need for any replacements.
A four-cylindered compression-ignition engine for vehicle applications, based on the Elstroe unit, is envisaged. This would produce 70 b.h.p. from a capacity of less than 2 litres and would, on this figure, be strictly comparable in performance with current spark-ignition petrol engines.