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 oil pressure, bearing clearances, viscosity, and lubrication systems.
| Identifier | ExFiles\Box 178\1\ img140 | |
| Date | 19th May 1926 | |
| - 7 - Hs{Lord Ernest Hives - Chair}/ACL/T19.5.26. greater influence of the two. Another reason why reducing the bearing clearances is more important than the main pressure is that even with no main pressure, if oil were fed to the crankshaft, it would still be forced out from the big end bearings due to the centri- fugal pressure which is independent of the main oil pressure. The viscosity effect is particularly noticeable when the oil is cold and all will have observed the high pressures obtained when starting a cold engine which rapidly falls as the temperature rises, due to the reduced viscosity permitting the oil to flow more freely through the bearings. A sudden drop in the oil pressure is usually taken as a sign of failure at some part of the system, such as a bearing or failure of the release valve, but a low pressure in itself does not necessarily mean that the lubrication is defective, because bearings having liberal clearances will allow the same quantity of oil to pass per min. at a much lower pressure without affect- ing the lubrication. We therefore see that a certain volume of oil can be circulated per min. in two ways, either by small bearing clearance and high pressure, or slack bearings and low pressure. For these engines the former method seems to be the more reliable of the two because high pressures can be employed which should tend to produce a greater equality of distribution whereas contd. | ||