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).
Issue of excessive blow-by in high power engines, its effects, and proposed solutions for the piston ring set-up.
| Identifier | ExFiles\Box 134\1\ scan0173 | |
| Date | 2nd December 1939 | |
| 1129 To Rm{William Robotham - Chief Engineer}/CTS.{C. Trot Salt - Carburation} from Rm.{William Robotham - Chief Engineer} c. Jnr.{Charles L. Jenner} Rm.{William Robotham - Chief Engineer}1/MH.{M. Huckerby}2.12.39. BLOW-BY ON HIGH POWER UNITS. The blow-by on the high power engines is excessive as you have observed. Whilst the evils of blow-by have been much exaggerated, it cannot be good for - (1) Carboning up the cyl. head. (2) Increasing crankcase pressure and so encouraging leaks. (3) Smell in the car via breather. (4) Idling. Air leaks past piston. (5) Sludging up oil. We therefore want to make the minimum alteration to our ring set-up to get the required reduction in blow-by.{R.W. Bailey - Chief Engineer} I do not think it necessary to go to four rings. My suggestions are - (1) Two gas rings and existing perfect circle replaced by L section. (2) Same arrangement as at present but slightly higher ring pressure and reduced amount of L section. I would like to know more about blow-by.{R.W. Bailey - Chief Engineer} (a) What is the rate of blow-by on a good and bad engine? (b) Is the measured rate of blow-by under load proportional to the noise heard and assumed to be blow-by when the engine is idling ? (c) Is the appearance of the breather a good indication of the amount of blow-by that can be measured as taking place ? | ||