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).
Letter providing general information on the function and components of an Oil Tester instrument for car types.
| Identifier | ExFiles\Box 165\3\ img116 | |
| Date | 21th July 1935 | |
| x 6033. Instruments general London, July 21, 1935. Messrs.Rolls-Royce Limited, Nightingale Road, Derby. Gentlemen:- As requested by Mr.West, at our last interview, please find herewith, a photo of our Oil Tester body, with overall dimensions marked, and a blueprint showing the dimensions of the indicating meter, which is mounted on the instrument board. In view of the fact that we have not any literature printed, dealing with our Oil Tester(car type), I have tried to outline a little general information, in the following paragraphs. The Oil Tester is a scientific instrument, designed to show the true state of crankcase motor oil. In less than a minute it gives the motorist a definite and authentic reading---tells him whether the oil in his motor is safe or unsafe, for further use in his motor. The Oil Tester indicates the degree of contamination of the oil, by carbon, road dust and fine metal particles. The results of a test are easily read on a dial, mounted on the instrument board, and marked off in divisions, Clean, Fair, Dirty, and Bad. An indicating needle points to one or the other of these divisions, according to the state of the sample under T test. The test is effected by means of light rays, passed through a film of oil, and registering upon a Photronic Cell. This Cell generates current directly from the rays of light, and the current generated, is always directly proportional to the light intensity. The degree to which this light is obscured by the minute particles of gritty material in the contaminated oil, determines the movement of the needle on the dial of the meter. There are only four principle parts to the Oil Tester. A "window" consisting of two specially ground lenses, with a narrow space between them, through the oil is forced. A small electric lamp on one side of the "window". A Photronic Cell on the other side of the "window". The Cell measures how much light comes through the "window" when the oil is passed between the lenses. A meter on which a needle registers how much light has passed through the oil, and consequently, how clean or dirty, the oil may be. If the oil is reasonably clean, enough light passes through it, to make the needle on the meter point to Clean or Fair. If, on the other hand, the oil is dirty, this dirt, although invisible to the human eye, blocks the passage of the light rays, and the needle points to Dirty, or Bad, as the case may be. We must admit that while the instruction book furnished with any car, may state a definite mileage at which to drain the crank-case oil, this stated period does not give every motor absolute protection from the harmful effects of contaminated oil. For the simple reason, that no two motors are handled in the same manner by their drivers. | ||