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).
The 'Smith' Air Filter with Silencer & Warning Whistle, its function, and maintenance.
| Identifier | ExFiles\Box 135\4\ scan0114 | |
| Date | 20th July 1931 guessed | |
| THE “SMITH” AIR FILTER WITH SILENCER & WARNING WHISTLE. IT is impossible to exaggerate the importance of maintaining a perfectly clean supply of air to the carburetter intake, as grit and dust can cause untold damage to the engine, with a consequent drop in efficiency due to the pistons and cylinders wearing much more quickly than they normally should. This danger can be entirely overcome by the fitting of an air filter, but to maintain all round efficiency the air admitted must not only have every particle of dust removed, but it must not restrict the air flow to the carburetter in the slightest degree, otherwise full power will not be developed and the petrol consumption will be increased. EFFICIENT FILTERING. The “Smith” Air Filter is self contained, and fulfils all the requirements outlined above. It is designed to fit directly on to the intake of the carburetter, so that all the air passing to the engine must come in contact with the filtering medium, which is in the form of a thick pad made of wire and fabric twisted and entangled together, saturated with oil, and positioned between two grids. Dust or any foreign matter immediately adheres to the filter, allowing nothing but perfectly clean air to pass to the engine. The material used for the filter carries sufficient oil to saturate all foreign matter collected, with the result that it becomes more and more efficient. AUDIBLE WARNING. The gradual accumulation of foreign matter on the filter will “build up” to a point when it begins to restrict the free passage of air, as any filter worthy of the name must do. Immediately this stage is reached, air admitted via the whistle gives audible warning of the need for cleaning. This novel and most important feature prevents any possibility of interference with the free passage of the air at any time to the engine without it being noticed by the driver. SILENCING. Another important feature embodied in the design is the silencer, which is conveniently placed opposite the intake. This very effectively damps out all sound caused by the rush of air past the throttle. THE “SMITH” AIR FILTER WITH SILENCER AND WARNING WHISTLE. Fig. 1. Type AF. Fig. 2. Type AFN. The standard design is as illustrated at Fig. 1, but for cars where bonnet clearance is limited a special narrow design as illustrated at Fig. 2 is used. INSTRUCTIONS FOR CLEANING FILTER. Standard Design, Fig. 1.—Remove silencer cap by slightly relieving the pressure on one retaining spring. Withdraw outside grid and filter pad, wash in petrol, and dip pad in oil (Castor oil preferred). Allow to drain and re-fit. Narrow Design, Fig. 2.—Take off the two nuts and withdraw outer casing and filter off the studs. Wash in petrol and dip in oil (Castor oil preferred). Allow to drain and re-fit. | ||