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).
Instructions and considerations for piston design, addressing issues like gummed pistons and oil consumption.
| Identifier | ExFiles\Box 16\1\ Scan189 | |
| Date | 23th May 1927 | |
| To RG.{Mr Rowledge} Hs.{Lord Ernest Hives - Chair} c. to Wor.{Arthur Wormald - General Works Manager} BY.{R.W. Bailey - Chief Engineer} E.{Mr Elliott - Chief Engineer} x741 R1/M23.5.27. GUMMED PISTONS - RR. Cs. & Fs.{F. Steele} X.3996 X.741 AND CAR WORK. X.8040 X.2103 Y2603 As before instructed let us make no pistons for any purpose, such as H.C., unless they are - (1) Ideal in shape. (2) and let the top ring be between .250 and .350 from the top. The .150 was an old dimensions originated when the top band of the piston carboned up, and was permitted for comparison. (3) If it is found advantageous let us not run below a certain oil consumption as well as above, i.e., both a maximum and minimum. Only the most reliable fuel and oil should be recommended by us: evidently either, if bad, can ruin the engine by gumming the rings etc. Let us use only one, and the latest and best design of piston, rings, pins, scrapping all older work that has proved unsatisfactory or doubtful practice. (4) Let us use a perfect circle ring at top - (i.e. groove in face with holes through) if this proves good. Very many times I have asked for this to be tested as a scraper ring. I was not aware that we ever made pistons where the full dia. ran beyond the cyl. bore into the combustion clearance. I should not expect this to be good. R.{Sir Henry Royce} | ||