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 specifications and design modifications for Phantom and 20 HP models.
| Identifier | ExFiles\Box 66\1\ scan0180 | |
| Date | 18th October 1928 guessed | |
| contd :- -2- of the pistons we wish to get adopted :- 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 20 HP. 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. | | 20 HP. | 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 20 HP. 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 clear- ances and dimensions are found for them, such as the grinding of the piston clearances, and stiffness of the rings. R.{Sir Henry Royce} | ||