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).
Graph of torsional vibrations against crankshaft RPM for a Flat 12 Cylinder 2 Stroke engine.
| Identifier | ExFiles\Box 132\2\ scan0191 | |
| Date | 26th October 1940 guessed | |
| SHEET 2 FLAT 12 CYL 2 STROKE TORSIONALS. The calculations are for an engine of Ph.III dimensions (3 1/4 x 4 1/2) having an undamped crankshaft. On a 12 cyl. 2 stroke engine the firing interval should be 30°. This is possible with a 90° V but not with a flat engine. These calculations have been made for a firing order in which 2 cylinders fire at the same time. FIRING ORDER A 1/6 3/4 2/5 B 2/5 1/6 3/4 1° Torsion amplitude at the free End of the Crankshaft. DEGREES Crankshaft R.P.M. LB/SQ. INCH. Maximum stress at the node. 3/ REV. MAX. AMPLITUDE @ 4150 RPM = 13.4° 2/ REV. MAX. AMPLITUDE @ 6220 RPM = 9.2° Graph Peaks: 12, 11, 10, 9, 8, 7, 6, 5, 4 | ||