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).
Experiments with different piston designs and lubrication oils to resolve engine knocking issues.
| Identifier | WestWitteringFiles\C\August1919\ Scan62 | |
| Date | 29th August 1919 | |
| Contd. 4. EH4/LG29.8.19. We could not find any appreciable advantage with this. We have another set of pistons in another alloy which have not yet been tried. We have also tried the present pistons with the rings raised so that the top ring is 1/4" from the top of the piston. We found with this there was a slight improvement X. 3402 We have also tried a sleeve type piston. (Mr. Royce will remember I suggested this a long time ago by means of preventing piston knocks by making use of a double oil film). We required so much clearance in order to get this piston free. We found with this that we still got knocks. With this piston we had to have a minimum clearance of .025". Lubrication. X. 2631 We have run 49-GB with quite oil continuously in operation. The car runs quite satisfactorily and gives no trouble on the road. The only sign of smoke from the exhaust is after running slow for 15 to 20 minutes. On examination of the cylinders we found that one of them was very wet with oil. Even with this amount of oil we could not cure knocks when starting up cold but the oil did have the effect that the knocks dissappeared more quickly. We have tried different brands of oil and find that the Castor Oil is the best oil, if anything, to prevent the knocks. We have also carried out several experiments to find out exactly which part of the piston it is which knocks. So far, we have proved nothing definate. We have Contd. R R 530Y (800 11) (R L 219 10-1-19) C 5221 | ||