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).
Technical bulletin regarding oil flow, observing results, and the life of an oil filter.
| Identifier | ExFiles\Box 135\3\ scan0108 | |
| Date | 24th April 1936 guessed | |
| -2- OIL FLOW. The flow of oil through the filter when first fitted is considerable which ensures that the sump is cleaned up of foreign matter very quickly leaving only colloidal matter. As the filter bed, composed of foreign matter, builds up on the filter paper discs even colloidal matter is removed. The flow, however, is reduced to approximately ½ to 2 gallons per hour, which is nevertheless sufficient to maintain clean oil in the sump. It must not be assumed that because the oil flow appears to be small that the filter is not doing its work, it is in fact a sure sign that the filter is doing its job. The efficiency of the filter must be judged by the condition of the oil in the sump. OBSERVING RESULTS. The efficiency of the Smith Filter is so high that a short time after fitting it will maintain absolutely clean oil in the sump throughout its working life. This can easily be observed by noting the condition of the oil on the dip-stick which will be bright and clear. We recommend chromium plating the dip-stick as this makes it very much easier to visually note the condition of the oil. When the oil on the dip-stick becomes black, then the filter needs replacing. LIFE OF FILTER. In the past filter manufacturers have indicated that a filter should be replaced after, say 8,000 or 10,000 miles. This is necessary as these filters have such a low efficiency that the oil in the sump is always black in colour and it is impossible to judge when a filter requires replacing. With the Smith Filter fitted, however, one can observe the cleanliness of the oil on the dip-stick, and the filter must be replaced when the oil becomes dark or black on the dip-stick irrespective of the mileage run. It is quite wrong to decide when to change a filter by the mileage run as the amount of dirt it has to take out must obviously depend on the condition of the engine, etc. From our experience the Smith Filter will give a useful life of between 10,000 and 20,000 miles, but it must be remembered that this mileage is based on the assumption that new oil is used in the sump when the filter is fitted. If, however, the oil has been in the sump some considerable time the life of the filter will be shortened by the amount of dirt in the oil which will be removed shortly after the filter is fitted. COLLOIDAL GRAPHITE. contd: S.P.81 S. SMITH & SONS (Motor Accessories) LTD., CRICKLEWOOD WORKS, LONDON, N.W.2. CONTINUATION NO. | ||