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).
Paper titled 'Cylinder Bore Wear' by Alex Taub, including communications on the subject.
| Identifier | ExFiles\Box 132\5\ scan0121 | |
| Date | 1st January 1937 | |
| 24 COMMUNICATIONS ON CYLINDER BORE WEAR now among the best. This engine was now being fitted in some cases with a steel liner and piston rings with a supplementary tension from a spring behind the rings. This gave good results and had lengthened the average bore life in the United States. However, the engines fitted with spring-backed piston rings only were doing just as well as those with liners and the special rings. This should not cause a rush to use steel liners and spring-backed rings, because the manufacturers who led in oil control and low bore wear in the United States did not use either. Mr. Wilson’s statement was informative and in the main corroborated his own experience. Mr. Wilson was probably correct that the pearlitic iron liners would do as well as hardened liners. This type of iron had been in use long enough by his company to eliminate any doubt. However, was Mr. Wilson satisfied that service of the door-to-door delivery type could be performed with pearlitic iron only? Would his ingenious colleagues meet this, without an acid-resisting surface? He must assure Mr. Young that he would even dare to offer a metallurgical suggestion. It should be permissible, however, to report facts—even though they be metallurgical. He reported that a certain mixture was being used, and Mr. Young, who was undoubtedly a leading metallurgist, promptly raised his eyebrows. This fact must be pointed out: pearlitic iron might prove to be the best ring material in the future. However, something like five million cars per year were going into use and only about 10 per cent were thoroughly satisfactory. Nevertheless, ring life was being increased even among the best, by treatment of the ring contact surfaces. Mr. Young’s pearlitic iron rings might not require this process—might in fact be better without such treatment than the present rings were with treatment. The burden of proof was his. He would certainly watch this development. 1 Cylinder Bore Wear By Alex Taub* The author has been responsible for the design of engines for a motor car in which the life of the cylinder bore over a period of ten years and a total of eight million engines is 12,000 miles per 0.001 inch wear. The factors contributing to this result are as follows: (1) thermostatically controlled cooling for water at a minimum temperature of 145 deg. F.{Mr Friese}, preferably 160 deg. F.{Mr Friese}; (2) crankcase ventilation to eliminate the effects of blow-by in the oil sump; (3) adequate oil supply to cylinder bores; (4) complete control of the lubricant at the piston rings, not at the source of supply of the oil; (5) control of blow-by at the rings; (6) leanest possible mixture ratios for general operating conditions; (7) close attention to the type of fuel used to ensure that it is properly vaporized; (8) a uniform hot metal temperature; and (9) an accurate spark advance mechanism. All these factors are discussed by the author in detail, special attention being paid to the testing of piston rings in the laboratory, the correct use of thermostats, and crankcase scavenging. Though no one simple theory covers the probable causes of cylinder bore wear, this does not mean that corrosion should be disclaimed as a prime factor. Recently, at the General Discussion on Lubrication and Lubricants arranged by the Institution, the general reporter, in summarizing the results of the discussion on engine lubrication, observed that there were two schools of thought regarding bore wear, one which believed the corrosion theory, and one which disbelieved it. The author was erroneously placed among the negatives. The author is certain that no one quarrels with the corrosion “theory”, but he does not think it should be considered as the only factor. Bore Wear in the United States. Recently the author stated that, years ago, he had worked on the question of corrosion, or etching as it was called in America. Investigations carried out by Mougey of the General Motors Corporation on the factors affecting etching or abnormal wear, led to the installation of thermostats and crankcase ventilators in all General Motors’ products. By 1931 this work was completed and a definite improvement in regard to wear ensued. Continuance of this work led to further improvement and, by 1934, reboring of the average American car, after running less than 50,000 miles, was usually unnecessary. Reboring might have been imperative in a few cases after running 30,000 miles, but they were very few. The average mileage before reboring is required is about 70,000 miles. It is the author’s contention, based upon his experience and observations here and in America, that the bore wear situation in Europe falls very much below this standard. The author has discussed † the wear of forty American cars, all 1936 models, which showed, except for three cars, an average of 5,700 to 7,000 miles per 0.001 inch of wear. The average rate for the same cars in 1937, with the same exceptions, was slightly lower because, in several cases, No. 1 cylinders showed higher wear than the rest. The three cars held out as exceptions in 1936 included one showing 3,500 miles per 0.001 inch wear, and two showing 12,000 miles per 0.001 inch wear. It is interesting to note that, for 1937, the car with the poorest rate of wear is still the poorest, and that the two cars at the top of the list are still at the top. This is the result, not of minor changes or of a laboratory experiment, but of conditions which, for two years, have covered an entire industry, representing 90 per cent of the world’s production of motor cars. To clarify the account of these test conditions, it may be added that a major oil company which ran an independent test with six cars from the 1936 group for 100,000 miles, found an average bore wear of 140,000 miles per 0.001 inch. This was unquestionably an easy test, whereas the test referred to for the entire American industry was comparable, when fairly severe public usage and considerable winter driving were taken into account. To deny that the cylinder wear problem exists in England does not solve the problem. The industry has been offered austenitic sleeves and rings as a remedy. Satisfactory results are obtained abroad without these expensive products. Why, therefore, should the industry here be condemned for insisting that bores with a life of 75,000 miles are available in the form of sleeveless cylinders with cast iron rings ? * Vauxhall Motors, Ltd. † Paper read before the University of London. See Automobile Engineer, 1937, vol. 27, p. 134. | ||