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).
Modification to address over-oiling on the vacuum pump by discharging its exhaust into the crankcase.
| Identifier | ExFiles\Box 64\1\ scan0050 | |
| Date | 22th August 1929 | |
| X7510 To By.{R.W. Bailey - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to E.{Mr Elliott - Chief Engineer} Wor.{Arthur Wormald - General Works Manager} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} 6/MJ. 22.8.29. OVER OILING ON VACUUM PUMP. ------------------- X.740 X.3503 X.7510 (Taken from Report Book) With a view to overcoming the loss of oil, and the unsightliness of oil dripping from the carburetter air intake, occasioned by oil finding its way through the exhaust port of the vacuum-pump; it was thought desirable to allow this exhaust to discharge into the crankcase. The advantages gained by this scheme are: (a) complete freedom from the effects of over-oiling (when present) (b) no exhaust pipe from the vacuum pump would be necessary; as a passage could be drilled in a modified cylinder casting, leading the exhaust directly into the wheel-case. (c) No vacuum pump silencer would be necessary. Against this, the only apparent disadvantage is the slight dilution of the crankcase oil by condensed petrol vapour. The petrol delivery of the autovac is unaffected by this arrangement. Tests have been carried out wdth a vacuum pump which overoils badly. When the engine had run for four hours at 1500 r.p.m., the vacuum pump had discharged 17 c.c. of oil from its exhaust pipe. On analysing this oil it was found to contain 6% (i.e.,1 c.c.) of petrol. The dilution of the xx crankcase oil (assuming it contained one gallon) would thus be .0055% per hour at an engine speed of 1500 r.p.m, which is negligible as this figure represents a very bad pump. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||