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).
Piston features and ring dimensions for Phantom and 20HP chassis.
| Identifier | WestWitteringFiles\T\2July1928-December1928\ Scan143 | |
| Date | 17th October 1928 guessed | |
| (2) We want 3 narrow rings and a perfect circle ring all pinned as shewn on LeC. 2490. for both chassis. We understand you are following LeC. 2577. type B. for the 20HP. The following are the features of the pistons we wish to get adopted:- | | CROWN. | TOP BAND | RING. | BETWEEN RINGS. | PERFECT CIRCLE RING. | TYPE. | |-----------|----------|----------|-------|----------------|----------------------|------------------------------------------------| | PHANTOM. | Flat top.| .250 | .100 | .125 | .175 | } Single bolt pedestal, all rings pinned. | | 20HP. | Ditto | .200 | .087 | .100 | .150 | } | There should be a stiffening ring or rib of some kind at the bottom of skirt. The only modification from this would be the 20HP. with diagonal webs - LeC. 2577. To avoid waste of time we think it is better to work on no other type or proportion until these have proved wrong, as we believe they are right providing the best clearances and dimensions are found for them, such as the grinding of the piston clearances, and stiffness of the rings. R.{Sir Henry Royce} | ||