References were made In cable news recently to a' new heavy oil engine invented in New Zealand, to which British experts were paying much attention. This engine is Identified by the Dunlop Perdriau Rubber Co., Ltd., as the Edlin-Stewart, a sleeve valve two-stroke in- vented by two New Zealanders, and which Is practically a compound reciprocating in- ternal combustion engine.
Each cylinder contains two working pistons, one of the ordinary design, and the other ta the form of a moving sleeve with the top end closed. This sleeve-piston combination performs the functions of primarily com- pressing the explosive mixture, transferring the gas into the combustion chamber, and participating in the power stroke. The crank- shaft has three throws for each cylinder; the ordinary piston rod connects with the centre one, whilst those set on each side extend some distance above the top of the standard piston, where they operate m a chamber sur- rounding the cylinder wall, and are attached on opposite sides of the moving sleeve. The piston bearing and the two sleeve bearings are set at angles of 180 degrees, the result being that as the crankshaft revolves the piston comes down and the sleeve moves up the cylinder. A second sleeve, which is stationary, Is provided over which the auxiliary piston or sleeve, slides down overlapping the top portion of the fixed sleeve, inside of which the ordinary piston reciprocates. The effect of this construction is that as the sleeve moves down, it draws into the head of the cyclinder a gaseous mixture direct from the carburettor. This mixture Is compressed as the sleeve moves to the top of the firing stroke, when a port in the sleeve-coinciding with a port in the cylinder-allows the com- pressed mixture to be transferred under velocity, Into the explosion chamber between the piston-head and inside of the moving sleeve. As the crankshaft revolves the sleeve and ordinary piston move towards each other, compressing the explosive mixture, which Is fired at the height of its compression by an ordinary sparking plug. An additional port is also actuated to permit the exhaust gases to escape. The burning of the mixture exerts Its power by forcing the piston down- wards and the sleeve upwards, thus Imparting two impulses to the crankshaft. This double expansion of the explosive charge converts a larger number of heat units Into power than does the ordinary petrol four-stroke com- bustion engine. The gain Is said to amount from 40 to 50 per cent, from a given size of
engine.
By this mechanical construction, crankcase compression-one of the undesirable features of the two-stroke engine-Is eliminated; whilst the temperature of the exhaust gases is very materially reduced and an extraordinary thermal efficiency attained. At all ranges of speed the engine is said to be remarkably free of vibration, owing to the perfect balance
obtained.
The new engine Is Ingenious and yet sur- prisingly simple; and Judging by its reception by English experts, Its future is promising. If It lives up to its promise, then possibly it may yet mark a new era ta the history of Internal combustion engines, for by Its use a four-cylinder engine would give the smooth even torque of an "eight" with approximately only half the weight and size.
Originally Posted by G Jones
Sorry to drag this up again - but only just found this thread (probably got too much time on my hands over the "festive" season) - thought it might interest someone...
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