Something Different

Manawatu Times, Volume LIV, Issue 7268, 22 September 1933, Page 11

Something Different

A compression ignition engine of a most unusual and original typo is now being produced commercially by the Junkers factory at Dessaug,. Germany It works on tho opposed-piston principle which has been previously _ employed successfully in Diesel engines, and is primarily intended for use m heavy vehicles. Engines with two, three and four cylinders in lino are now being fabricated, and by the extensivo uso of light alloys it has been found possible to obtain a good power-weight ratio of about 141 b. per developed horse-power. Although that figure is well in excess of the normal ratio ot petrol engines, it is remarkably low. In each cylinder of the Junkets engine there are two pistons which move in opposition to one another, tho lower one being connected to the erankskaf in tho customary manner. But on cither side of the main throw of the crankshaft are supplementary throws which are coupled by rods to a crosspiece, which is attached to the upper piston. . When both pistons aro at the limits of their travel, the exhaust gases escape through suitable ports, while, air which has been pro-compressed is lorced through the inlet port and onsurcs thorough scavenging of tho gassos. Ihe next movement in the cycle of operations is that the pistons approach one another, thus compressing the air m the cylinder to a degreo which causes ignition of tho fuel oil, which is injected near the centro. point of the cylinder at the moment when the pistons approach their top dead centres.

Tho explosion pressure is high, but tho balancing effect between the opposed pistons is such that tho load on tho maain crankshaft bearings is not abnormal.

Tho engine works on a two-stroke cycle, and when tho pistons which have been forced apart by the explosion of the charge reach the end of their firing strokes the exhaust ports are at once uncovered, compressed air is admitted at the top of the cylinder, and the next compression stroke begins. It is said that the two-cylinder engine develops 60 b.h.p. at 1,550 r.p.m. The stroke of the upper piston is shorter than that of tho lower. In tho case of the engine referred to, it is 96 nun., as compared with 144 . m.m. It is thought that bccauso of its compactness, this new Junkers unit will prove to be useful in passenger vehicles whero chassis space is a serious factor.