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).
Report comparing single cylinder head and piston configurations for a Bentley engine, with accompanying diagrams.
| Identifier | ExFiles\Box 134\1\ scan0113 | |
| Date | 23th December 1938 | |
| 1129 To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} c. Da.{Bernard Day - Chassis Design} c. Da{Bernard Day - Chassis Design}/Jnr.{Charles L. Jenner} c. Da{Bernard Day - Chassis Design}/McS. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}1/MH.{M. Huckerby}23.12.38. SINGLE CYLINDER HEAD COMPARISON. We give herewith a report of several tests that have been carried out on the above engine including a comparison of the ramp head both with raised crown and flat topped standard pistons, together with a further investigation of the standard Bentley cylinder head. Regarding the ramp head, we find that when using raised crown pistons there is a definite drop in power over the whole range (Curve b), these being compared at the same 6.6 : 1 compression ratio with flat pistons. Adhering strictly to Taub's theory of raised crown pistons we find that at 7.3 : 1 compression ratio the power up to 3000 R.P.M. is identical with flat topped pistons at 6.6 : 1, and above this speed the power with the latter is even better. [Left Diagram] No 1b & 1d RAMP HEAD 6.6:1 RATIO STANDARD PISTON PLUG IN EXHAUST POSITION [Right Diagram] No 2b & 3b RAMP HEAD 6.6:1 & 7.3:1 RATIO CROWN PISTON & PLUG IN EXHAUST POSITION | ||