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).
Comparison of valve opening areas for different engine designs, specifically comparing Aspin and BGO types.
| Identifier | ExFiles\Box 134\5\ scan0010 | |
| Date | 27th June 1940 | |
| THE LANDS HAVE BEEN MADE PRO RATA TO THE SIZE OF THE VALVE FOR THE 5.5 BORE ENGINE DEVELOPMENT VALVE OPENING AREAS - OPTIMUM ASPIN v BGO Graph Y-Axis: AREA OF VALVE OPENING [] Graph X-Axis: TIMING ANGLE° DEGS CAMSHAFT. Graph lines: ASPIN A, ASPIN B, BGO. THE LARGEST POSSIBLE AREA OF OPENING OF THE ASPIN VALVE IS 27% OF THE PISTON AREA WITH A DURATION OF 130° AS SHEWN ON THEIR DRAWING C144. WORKING ON THESE LINES AND MAKING THE VALVE AS BIG AS THE CYLINDER SPACING WILL PERMIT WE FIND THAT THE AREA DIAGRAM IS BETTER THAN BGO (REFER ASPIN A). NOW I SUGGEST IF WE SHORTEN THE DURATION WE GET A TIMING WHICH IS BEYOND DOUBT. SEE ASPIN B, THE AREAS ARE OF COURSE LESS BUT STILL COMPARE FAVOURABLY AS INDICATED. Diagrams: ASPIN A: 2.57[], 68°, 62° ASPIN B: 2.45[], 59° Measurements: 4.15, 3.5 Timing Diagrams: RR.BGO.: EX 244, 48 1/2°, 54°, 234 1/2 INLET ASPIN A: 6°, 10°, EX 234°, 48°, 260° INLET ASPIN B: 6°, 6°, EX 234°, 48°, 236° INLET, 50° Stamp: ROLLS ROYCE LTD PRINT ROOM DEC 28 1940 DERBY | ||