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).
Specification drawing for Phormicast piston rings, detailing dimensions, types, and tolerances.
| Identifier | ExFiles\Box 148\1\ scan0073 | |
| Date | 21th March 1939 guessed | |
| LIMITS ON RING GROOVE WIDTHS + .0015" + .0025" 3.11024 .00866 3.11890 3.119 -10 3.14961 .00945 3.15906 3.159 -10 3 RINGS 4.5 m/m RING 79.22 m/m +.000" -.010" DIA. 80.247 m/m +.000" -.010" DIA. S.D.O. CORNERED PLAIN EXS 1550 EB.2844. PARTICULARS OF PHORMICAST RINGS RINGS PER PISTON 1 OFF PLAIN 3 1/2" x 3/32" x 3.810 m/m 3.556 m/m 1 OFF CORNERED 3 1/2" x 3/32" x 3.810 m/m 3.556 m/m 1 OFF S.D.O. 3 1/2" x 4.5 m/m x 3.810 m/m 3.556 m/m ALL BUTT JOINTS .09375 .0015 .09525 .095 +1 -0 .177165 .0015 .178665 .1785 +1 | ||