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).
Engine bearing loads and supercharger development, comparing American and British technologies.
| Identifier | ExFiles\Box 27\3\ Scan214 | |
| Date | 15th May 1939 guessed | |
| 8. scheme under development. Bearing loads are comparable with those of Bristol engines, but it was stated that on one occasion a Pratt & Whitney engine was dived at 4000 RPM which gave a bearing pressure of 10,000 lbs/Sq.in. without damage to the bearing, which is still in service. Mr.Hobb said that Junkers have a big end bearing on a new bigger V-12 engine which has a maximum pressure of 14,000 lb/sq.in. The operating temperature of American big end bearings appears to be much lower than that of British radial engines. The oil returns on American engines are much higher than ours and the temperature rise of the oil from the oil inlet to its exit from the bearing past the ends of the connecting rod is only about 17°C, as measured by a thermocouple placed in the spray of oil as it leaves the bearing. This lower operating temperature must have a very big influence on the behaviour of the bearing. Blowers Heretofore all supercharger development has been carried out by the General Electric Company, but both Wrights and Pratt & Whitney are now taking a much livelier interest in supercharger design and development. Both Companies are against doing any work on the exhaust turbo blower as they feel that if it has taken the Army so long to develop with so little to show in the way of results, then no private firm could afford to undertake the work. In spite of this, from one comment I heard, I would say that Pratt & Whitney are doing a little work on low prioritym while Mr.Nutt in his Paper read before the S.A.E. expressed hopes that the next five years would see considerable developments in this supercharger. Wrights have a 2-speed blower in production, and are working on a 2-stage blower. Pratt & Whitney did not take up the 2-speed blower because they said the Army specifications stated that no points would be given for | ||