Technical description of the super-charger's control mechanism, carburetter details, and the vehicle's road performance.
| Identifier | ExFiles\Box 22\5\ Scan114 | |
| Date | 2nd July 1924 guessed | |
| 3 leads the petrol to the small impeller chamber, whence normally it flows under the ordinary tank pressure through a filter to the carburetter, which it enters through another small filter. Method of Control. Such, in brief, are the constructional details of the super-charger; it is brought into use merely by an additional movement of the accelerator pedal. (Below) Considerable wind resistance was offered by the rough test body. The battery box is hinged in brackets beneath the frame side-member, and may be swung out for inspection, as shown. of fully depressing the pedal engages the small multi-disc clutch, and the air impeller immediately starts to rotate at high speed. At the same time the movement of the accelerator pedal also closes the butterfly valve in the normal air intake, so that the compressed air from the blower alone supplies the carburetter. Additional fuel also is supplied by the action of the small impeller in the fuel chamber above the blower, the action of the two being so proportioned that the fuel supply is maintained at the necessary level. An important point to be remembered is that the carburetter and air inlet system must be quite air-tight. The carburetter itself has an annular float operating a needle valve to control the level in the ordinary way. A slow-running jet is arranged at one side, and admits a small proportion of mixture above the butterfly throttle valve immediately over the choke tube. Into the choke tube projects a small pipe, fed from a well at the base of the float chamber, and the jet itself is a bell-shaped cap in which are small spraying holes. This is held on the end of the jet tube by means of a spring-loaded plunger projecting into the carburetter from the upper side. Both jets are, therefore, very accessible, and may be instantly removed for cleaning or adjustment. A plunger projects downwards into the well at the base of the jet tube, and terminates in a small disc valve held normally closed by a spiral spring. On the throttle spindle is a triangular cam which, when rotated as the throttle opens, depresses the plunger and allows more fuel to pass to the main jet. A feature of the carburetter is that by rapidly opening the throttle a small amount of petrol is sprayed out of the main jet by the depression of this plunger and valve. With four passengers the test hill was ascended from a standing start on second gear at an average speed of 16 m.p.h., and on first and second gears at 17 m.p.h. The long cantilever rear springs are fitted in the channels of the frame side-members. A special mounting is employed for the mid points of the springs, while the ends are free to slide. Road Performance. Concerning the performance of the car on the road, it is sufficient to say that in normal running, and without the super-charger in operation, it is a good example of all that a docile, quiet, and smoothly operating touring car should be. The engine is efficient, but not of the super-efficient high-compression type, and traffic may be negotiated on top gear without any necessity for slipping the clutch. The steering is very light, and possesses a good degree of caster action; the controls all function easily, and call for a minimum of muscular exe(Aero Engine)rtion, the clutch and brake pedal, indeed, requiring exceptionally light pressure. The gear change is by no means difficult, the brakes are effective, and the suspension obliterates any sense of road shock, even on a really bad surface. It is, however, with the effect of the super-charger that we are at present more particularly concerned, and it is recommended that this should not be brought into use below a speed of 35 m.p.h. on top, or 25 m.p.h. on third gear. To depress the accelerator to its fullest extent is to change the character of the car completely. | ||
From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).