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 to Messrs. Smith & Sons Ltd. discussing the principles and performance of the General oil filter.
| Identifier | ExFiles\Box 135\3\ scan0222 | |
| Date | 8th January 1938 | |
| 1139 Rm{William Robotham - Chief Engineer}7/R.{Sir Henry Royce} 8th January, 1938. C.W. Nichols, Esq., Messrs. Smith & Sons (Motor Accessories) Ltd., Cricklewood Works, LONDON. N.W. 2. Dear Mr. Nichols, I was interested in what your Expert said about the General Filter. He, however, is evidently not aware of the way in which the replacement element is constructed. The principle of the General Filter is that it has a carbon pack at the bottom, which removes acidity and large pieces of foreign matter, and the filtering medium is then graduated throughout the element until before the oil leaves it has passed through an exceedingly fine strainer. Obviously by this construction the life of the filtering element for a good degree of oil cleanliness is many times that of the corresponding homogeneous surface area. The attached sketch illustrates what I mean. In our experience this filter is good for 10,000 miles on a P.III car before it requires renewal. I think that your Expert should have been careful before he told you that this filter was no different to the type filled with Fullers' Earth. In order to be quite fair to your filter, I should like one to test when I will give you a figure of merit for it compared with the A.C. Filter and the General Filter. Yours sincerely, | ||