THE twin-cylinder Rudge engine was first planned some little time before the war, and is now definitely announced as one of the range of models offered to the public during the 1920 season.
To those riders who favour the infinitely variable type of belt transmission, the new engine will make a special appeal, since the necessary limitation of the lower gears with this form of drive has rather ruled out the small Rudge models for heavy sidecar work in mountainous districts. The larger engine, therefore, supplies the extra power which is desirable, and, being of the full 998 c.c. capacity, should answer every requirement, and withal, may be expected to have more than ordinary speed, by virtue of the 3 1/2 to 1 top gear.
The engine, so far as externals go, and excepting the désaxé cylinder setting, is at once recognised as being characteristically "Rudge," for the chief details are similar to those of the well-known single model; the inlet valves being placed above the exhausts in detachable domes. A very clean exterior characterises the crank case, which is an aluminium casting, entirely free from ridges, designs, or lettering of any kind likely to hold dirt or interfere with ease of cleaning.
Roller Bearing Connecting Rods.
A T shaped induction pipe, which telescopes directly on to the inlet dome stubs and is there secured by clips, carries a vertical model Senspray carburetter, which depends between the cylinders.
Top feed to the float chamber is employed, and the air intake points downwards.
Neat valve lifters, similar to those of single-cylinder models, operate by means of small levers under the tappet heads, and the usual Rudge pedalling gear, rotating the engine through a positive acting friction device on one of the half-time wheels, is retained for starting purposes.
Rudge engines are noteworthy as being amongst the few made which are fitted with roller bearings in both big and small ends of the connecting rod, and this practice is followed in the twin-cylinder model. The application of rollers to the crank bearing of a V twin, in which both rods work on a common pin, is not without its difficulties, and the usual side-by-side arrangement was not considered perfect. In order to eliminate the short couple, which would otherwise exist, a peculiar construction of forked rods is used; the single rod works inside the double one, and the latter has a small stiffening piece bridging the two sides of the fork. A steel bush passes through the eyes of the rods, and is a floating fit in both; this bush bears on rollers which run between it and the crank pin, and these are the full width of the combined big end. The workmanship in this part is exceptionally good, ample provision being made for lubrication.
T.T. Frame Design.
Oil is carried in the tank behind the saddle tube, and delivered to the engine through a foot operated pump. The latter discharges through a short pipe into the crank case in such a way that each fresh charge of oil is injected between the two flywheels directly on to the big ends.
A type of frame popularised on the Rudge T.T. models is used on the 7-9 h.p. twin; it has a sloping top tube, and has a large tank holding a full two gallons of spirit. In other respects, also, the Rudge specification is followed. It is satisfactory to note that all the lugs employed in the frame are steel stampings, and that these, together with the connecting rods, flywheels, and other parts capable of being stamped, are manufactured throughout in the Rudge works.
The well-known Multi gear, with free engine clutch on the engine-shaft, is used, and this, in conjunction with the large reserve of engine power available, should render satisfactory service, even when a heavily laden sidecar is being towed; incidentally, the machine is neither too weighty nor too unwieldy for solo use, and should be an ideal fast touring mount.
The detail work is well carried out, and all the refinements associated with this make are included, such as screw-down greasers to the fork bearings, spring-up rear stand, hinged rear number plate, and mudguard extension, drop pedal foot-rest, and celluloid finished handle-bars, hubs, and gear lever; 550 x 55 mm. light car tyres are fitted on extremely heavy round base rims.
The Motor Cycle, November 13th 1919. pp 537-538
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