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).
Crankcase depression tests comparing different breather methods to manage oil vapour and prevent oil leaks.
| Identifier | ExFiles\Box 159\6\ scan0010 | |
| Date | 24th February 1937 | |
| 81371 Rm{William Robotham - Chief Engineer}/Gry{Shadwell Grylls} from Rm{William Robotham - Chief Engineer}/WB.{Mr Brazier/Mr Bell} Rm{William Robotham - Chief Engineer}/WB{Mr Brazier/Mr Bell}2/M.24.2.37. Crankcase Depression Tests. We have been carrying our experiments with the object of ridding the crankcase of the undesirable properties which are present in the oil vapour, which if allowed to accumulate will have harmful effects on the cylinder bores. It is essential that the atmosphere in the crankcase should never become stagnant. Two methods can be employed, either by pressure into the crankcase or by extractor breather. The latter method is preferred because in the former case an air cleaner would have to be fitted to deal with foreign matter in the atmosphere, in addition to the leaks from the joints. With an extractor breather the risk is eliminated, it has the advantage of helping to prevent oil leaks. It must not, however, be too efficient, otherwise oil will be extracted with a consequent increase in consumption. With this in mind we have made an extractor breather by means of a venturi fitted on the end of the existing breather pipe and which is well into the air stream. Attached are the figures taken at the venturi top of the breather pipe and the crankcase. They were taken every five minutes over a 200 miles run and an average taken at the varying speeds. Direction of wind is an important factor and was responsible for some variation in the figures. At the end of the run a thin coating of oil in the rear of the venturi proved its efficiency. Oil consumption was 646 mpg. Average speed 44.88 m.p.h. A repeat run with a standard breather showed a crankcase pressure reaching a maximum of 500 of water at the high speeds. Oil consumption 668 mpg. Average speed 46.4 M.P.H. Rm{William Robotham - Chief Engineer}/WB{Mr Brazier/Mr Bell} | ||