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).
Foreword explaining the function and efficiency of the Smith Oil Filter and its use with colloidal graphite.
| Identifier | ExFiles\Box 135\3\ scan0217 | |
| Date | 27th August 1937 guessed | |
| Foreword THERE is no doubt that an efficient oil filter may be an important factor in the life of an engine, particularly in regard to cylinder wear, because it is evident that if the oil in the sump is always pure and clean, minimum damage must result. A filter is incorporated, of course, to remove suspended foreign matter, however finely divided. If a sample of oil be taken from the sump of an engine fitted with an oil filter, and this oil is found to be dirty looking and discoloured, then it may safely be assumed that the filter is not effective. An efficient filter should maintain clean oil, as new, throughout the working life of the filter; oil should only become dirty when the filter is clogged up. In describing the new Smith Oil Filter we cannot do better than reproduce an article which appeared in the January, 1936, issue of THE AUTOMOBILE ENGINEER. After the filter has been in operation a few hours it is able to extract all traces of impurity from the oil, including colloidal matter. In actual practice the filter increases in efficiency because the impurities extracted from the oil collect on the filter units and form an even finer filtering bed than the units themselves. This is the reason why the oil emerging from the filter itself is star bright after it has been in service a short time. This building up of the filter bed on the papers naturally restricts the flow through the filter, but because of the extreme fineness of filtration it is able to keep the oil in the sump perfectly clean. COLLOIDAL GRAPHITE The question of colloidal graphite used in the sump for running-in purposes has been carefully thought out and allowed for in the design of the Smith's Filter. For those owners who wish to employ colloidal graphite during the running-in period of their engines we have arranged the filter characteristics so that its operation is gradual. At first colloidal graphite is allowed to pass, but after a sufficient period the filter bed builds up on the papers and the efficiency increases to such an extent that nothing is allowed to pass but pure clean oil. It should be noted that although colloidal graphite is allowed to pass in the early life of the filter, the filter is nevertheless still efficient and will not allow any foreign matter to pass through. Judge the efficiency of the Smith Oil Filter by the colour and cleanliness of the oil on the Dip-stick. | ||