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).
Article from 'The Motor' magazine describing the Smith's single-jet carburetter for high-speed engines.
| Identifier | ExFiles\Box 3\5\ 05-page020 | |
| Date | 21th December 1918 | |
| The Motor 498 21st December, 1918. SMITH'S SINGLE-JET CARBURETTER. An Entirely New Carburetter Especially Adapted for High-speed Engines. IN addition to the popular four-jet carburetter manufactured by Messrs. S. Smith and Sons (M.A.), Ltd., Great Portland Street, a new single-jet carburetter of the straight plain-tube type has been placed on the market and especially adapted for high-speed engines. The carburetter is entirely different in principle from any other known make. It is not a suction-controlled carburetter, where the engine suction controls petrol drawn from the jet or tubes, but it is a throttle-controlling jet suction carburetter. With the exception of the float there are no moving parts. It has only one jet besides having an outside adjustment of the slow-running, which has no influence over the main working of the carburetter generally speaking. To allow for variation of temperature there is an extra mixture-correcting device, which can be operated from the dashboard or otherwise, as convenient. By the use of this device a larger jet than is necessary can be fitted in the carburetter, which enables the engine to warm up quickly in cold weather, and directly the motor is hot additional air can be admitted, reducing the suction of the jet. Therefore, for starting and getting away quickly a rich mixture is provided. A special form of filter is incorporated in the carburetter itself, which is tantamount to ensuring that the jet itself will not become blocked. The sectional diagrams of the carburetter shown in both the horizontal and the vertical type have been well lettered so as to give a very clear idea as to the co-relation of the various parts. The petrol enters through a special detachable nipple below the float chamber, and strikes against the filter, so that any dirt or foreign matter will be thrown down the inclined passage-way and collected into the sump, this being of sufficiently large dimension to render it easily removable. The float chamber is the usual type, and it will be noted that the lid{A. J. Lidsey} is held in position by means of a spring catch, thus eliminating screws. This is not new, but it is a good point. The petrol then flows through the passage conducting it from the float chamber to the main jet, and it will naturally pass through this and rise to the level of the float chamber, thus bringing it up in the slow-running well immediately adjacent to the float chamber and the central delivery tube, which is screwed in above the jet. When the throttle valve is nearly closed the suction effort of the engine is exerted on the small hole on the right-hand side of the throttle communicating with the small standpipe in the slow-running well, and draws petrol from this, which mixes with the air passing beneath the taper-ended screw valve, which has an external adjustment for slow running. The air to the slow-running well is provided through the air passage leading from the throttle valve to the slow-running well from the holes in the throttle spindle and the throttle spindle bosses, which, in the nearly closed position of the throttle, are wide open. Presuming the throttle is now opened to speed up the engine, the suction effort will be diverted from the small hole of the slow-running device on to the delivery tube, which is placed in the centre of the choke, drawing the petrol already in this tube, as well as that contained in the slow-running tube. It will thus be seen that the slow-running device is now entirely out of action. Air is now rushing down through the holes of the throttle spindle to the slow-running tube and mixing with the petrol issuing from the main jet, and so out of the delivery tube, and is, in turn, mixed with the incoming main air entering at the main air inlet, which affords a very fine Sectional explanatory drawing of the new Smith single-jet carburetter, vertical type. DIAGRAM LABELS (Vertical Type): LEVER OPERATING AIR STRANGLER FOR EASY STARTING SLOW RUNNING ADJUSTMENT SCREW SLOW RUNNING DELIVERY PASSAGE LEVER FOR CONTROLLING AIR STRANGLER CAP FOR FLOAT CHAMBER AIR PASSAGE TO SLOW RUNNING WELL OLD TYPE OF SLOW RUNNING DEVICE THROTTLE VALVE SPINDLE MAIN AIR ENTRY FOR SLOW RUNNING DEVICE FLOAT NEEDLE COLLAR COVER OF FLOAT CHAMBER CHOKE TUBE THROTTLE VALVE FLOAT FLOAT CHAMBER PETROL LEVEL PETROL DOUBLE GAUZE FILTER JET DELIVERY TUBE MAIN AIR ENTRY PETROL NIPPLE SUMP FOR DIRT SUMP PLUG PETROL FROM TANK FILTER CONTROL - HORIZONTAL TYPE - Smith single-jet carburetter. DIAGRAM LABELS (Horizontal Type): SLOW RUNNING DEVICE SLOW RUNNING ADJUSTMENT AIR INTAKE AIR PASSAGE AIR VALVE THROTTLE VALVE SPINDLE FLOAT CHOKE TUBE DELIVERY TUBE JET PETROL NIPPLE FILTER 243 | ||