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).
Unit test report for the Spectre No. 3 engine, comparing its performance against the No. 2 unit.
| Identifier | ExFiles\Box 4\1\ 01-page232 | |
| Date | 28th January 1935 | |
| To E.{Mr Elliott - Chief Engineer} c. to Hsr. c. to Hy.{Tom Haldenby - Plant Engineer} <300 Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}14/KW.28.1.35. Unit Test of SpectreCodename for Phantom III No. 3. This engine fitted with semi-split type pistons (A.84546) and short duration camshaft E.86371 was down for power compared with No. 2 unit which had Aerolite pistons and Hs.{Lord Ernest Hives - Chair}1536 camshaft. Comparative curves are shewn on SP.{Mr Spinney}9. the power peak of No. 2 being 199.5 B.H.P. at 3750 r.p.m. and No. 3, 178 B.H.P. at 3500 r.p.m. whilst at speeds below 1500 r.p.m. No. 3 is slight better, developing 96.5 M.E.P. at 500 r.p.m. against 94 M.E.P. on No. 2 unit. From figures obtained on the Bentley we have drawn a calculated curve of No. 2 unit with semi-split pistons, giving a direct comparison between the two camshafts. As such, No. 2 unit develops 189 B.H.P. at 3750 r.p.m. the Aerolite pistons being responsible for 10 B.H.P. gain, and the Hs.{Lord Ernest Hives - Chair}1536 camshaft being better than the E.86371 camshaft by 11 B.H.P. The inlet open and exhaust close positions as checked with .020" clearance are identical in both camshafts, the former being 7º past T.D.C. and the latter on T.D.C. Hs.{Lord Ernest Hives - Chair}1536 is approximately 10º longer duration than E.86371, the inlet close positions being 53º and 44º past B.D.C. respectively and the exhaust openings 48º and 37.5º before B.D.C. The slow running on both No. 2 and 3 units is almost identical and fairly good, obtaining even light running at 250 r.p.m. advanced ignition and 300 r.p.m. retard. Under load these speeds come down to 150 r.p.m. and 160 r.p.m. In order to obtain good slow running it is necessary to run open exhaust to synchronise the throttle openings and the mixture settings as any little difference of setting is sufficient to upset the slow running. | ||