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).
Testing long pistons and the issue of piston knocks.
| Identifier | ExFiles\Box 48\1\ Scan107 | |
| Date | 1st September 1919 | |
| X.4190 To R.{Sir Henry Royce} from EH. c. to CJ. c. to E.{Mr Elliott - Chief Engineer} c. to BN.{W.O. Bentley / Mr Barrington} c. to E c. to Da.{Bernard Day - Chassis Design} c. to EP.{G. Eric Platford - Chief Quality Engineer} c. to BY.{R.W. Bailey - Chief Engineer} EH1/LCSO.9.19. X.4190 PISTON KNOCKS. Long Pistons of present design. The first one or two pistons of this type which we tested were very good for absence of knocks but now that we have had an opportunity of testing a number of them we find that the average of these pistons as regards knocks is very little, if any, better than the standard. We have had equally as bad knocks with these long pistons as we get with the present standard ones. We have also had cases of the long pistons knocking when hot. The pistons we have been testing are 2 1/4" longer than the standard ones. They weigh 2 lbs. 14 ozs. compared with 2 lbs. 8 1/2 ozs. of the present ones. We find we can only decrease the working clearance on the fitting portion which is at present .009" at the top to .006" at the bottom to .009" and .005". We have tried with annular grooves; this made no difference as regards knocking but if we had any width of groove we were liable to get a noise when the piston comes out of the cylinder bore. From the results of further tests with this long piston we do not think it is worth while spending any money in making patterns for this type of piston. Contd. | ||