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).
Article reprinted from 'The Motor' magazine about the modern method for running-in new engines.
| Identifier | ExFiles\Box 145\3\ scan0006 | |
| Date | 27th February 1934 | |
| Reprinted from The Motor February 27, 1934. “RUNNING-IN”—THE MODERN METHOD Recent Researches which Throw New Light on an Important Subject. Harm May Be Done by Over-care NEW engines, like young children, can be just as badly harmed by over-solicitous care as by thoughtless handling. This is one of the most important deductions that can be made from the latest research results—researches which have materially altered our ideas as to the best way of carrying out the running-in process. The engine of a new car turns stiffly for two reasons: first, the bearings and pistons are fitted tightly, with minimum clearances, and, secondly, the working surfaces, however carefully machined, are actually marred by microscopic irregularities. In the course of running-in these surfaces are burnished until smooth and, as a result, the clearances increase; both these changes tend towards a reduction of friction. Burnishing produces heat and yet, if the surfaces are to be smoothed with reasonable rapidity, a certain amount of pressure is essential. Consequently, the first and most important requirement is an adequate supply of lubricant which will reduce friction and carry away the heat generated. Not only must the owner-driver maintain the proper level in the sump, but in addition it is essential that he should use a reasonably light oil of the right grade. Particular care is necessary when starting a stiff engine from cold, because the oil is then thick and sluggish. It has to flow from the pump through a filter, a number of tiny passages and a series of tight bearings, before it is thrown into the cylinders by the rotating crankshaft; consequently very little oil reaches the bores and pistons during the first couple of minutes. This is where the over-cautious owner is apt to make his first mistake; he sets the engine at much too low an idling speed when allowing it to warm up. In so doing he extends the time required and reduces the quantity of oil thrown into the bores. The proper speed is from 1,000 to 1,200 r.p.m., which can be roughly judged from the fact that it is about the rate at which the engine revolves when pulling the car at 20 m.p.h. on top. Too low a working temperature does an engine far more harm than running too hot. The products of combustion condense on the cold walls of the cylinders and set up a corrosive action which has been shown to be one of the most likely causes of undue wear. Thermostat devices are of great assistance in this connection, a good alternative being the radiator muff. The golden rule for running-in a new car on the road is to avoid sustained periods of hard work, which will raise the oil temperature to an unsafe figure. Provided that this is remembered, short bursts of speed, at intervals, will be found advantageous. Otherwise, general running can be done with an engine speed not greater than 2,000 r.p.m., representing about 33 m.p.h. on top and 21 m.p.h. on the third gear. On the other hand, while over-revving is harmful, the engine should not be allowed to labour at full throttle; it is, therefore, better to change down on a stiff hill than to hang on to top gear, always provided that an excessive speed is not maintained. After 500 miles have been covered it must not be assumed that the engine has suddenly become transformed into a free-running unit. Care is still required and the best method is to increase the load and speed bit by bit, with more frequent full-throttle periods, so that by the time 1,000 miles is reached the car is being quite freely used. At this stage it is very important to have the filters cleaned, the sump thoroughly drained and to refill with fresh lubricant. The running-in process results in the abrasion of a certain amount of metallic dust which mixes with the oil and is harmful to the bearings. The whole process is undoubtedly assisted by using one of the many special running-in compounds now available which contain Acheson Colloidal Graphite in the form of tiny particles in suspension. The graphite forms a greasy film on the metal surfaces, safeguarding them from seizure and helping them to attain a smooth, long-wearing “skin.” [Image caption] Much wear and tear will be saved if the new car can be kept in a properly heated garage. E.{Mr Elliott - Chief Engineer} G.{Mr Griffiths - Chief Accountant / Mr Gnapp} ACHESON LTD. THAMES HOUSE, MILLBANK, LONDON, S.W.1 WORKS . . . . . . . . . . PLYMOUTH . DEVON Telephone: VICTORIA 5646 (3 lines). Telegrams: “OILDAG PARL LONDON.” MANUFACTURERS OF ACHESON COLLOIDAL GRAPHITE Temple Press Ltd., 5-15, Rosebery Avenue, E.C.1. | ||