MOTOR-CYCLING.

Press, Volume LXI, Issue 18550, 27 November 1925, Page 6

MOTOR-CYCLING.

DESIGN OF NEW MACHINES. HOW IT STRIKES THE NOVICE. The noTice in motor-cycling cannot help being struck by certain ideas when contemplating the design of a conventional present-day machine (says a writer in an.English publication). ; Why, for instance, does the exhaust pipe come out from the front of the cylinder in both side-valve and over-head-valve single-cylinder engines'? It seems to the beginner that it would be much more natural if the mlet and exhaust ports were interchanged, and the exhaust pipe had a straight run'to the rear of the machine, eliminating those wonderful curves which are such a preeminent feature of so many designs,; especially, sports machines. The placing of the silencer, a point which seems to trouble designers so much'at present,, would be simplified. A certain amount of supercharging effect might be obtained by pointing the air intake of the carburettor forwards —but the advantage of this is very doubtful. • A possible objection to; such a design is that the exhaust port would not be sufficiently, cooled; yet the rear cylinder of a V-twin shows no tendency to overheat. Being unconventional, such a lay-out might be considered ugly—as all deviations from standard practice are at first. - . ; .• I Another obvious point for lay-criti-cism is in the .design of the, ever-in-creasingly popular overhead-valve single-cylinder engine. Could noi the whole rocker gear be in some way attached to the tube running: under the tank? • It might be possible to have a little oil bath brazed on to this tube in which the rockers would move, or in which j an overhead camshaft would have its I bearings. The result of this would be a beautifully clean ■ and well-cooled cylinder head, free from such encumj brances as rocker bearing arms, stiffI emng plates, etc., and at the same time thg rockers or camshaft would work in cool and well-lubricated bear r ings. Additional advantages would be a low frame, yet giving plenty-of ground clearance, improved accessibility a lighter engine, as the cvlinder : head would not have to be so heavy; I and, .probably, decreased cost of manu- [ lacture.