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 Road Wheel Horse Power vs. Road Speed for a Phantom II to achieve 100 MPH, with comparisons to Bentley models.
| Identifier | WestWitteringFiles\V\March1931-September1931\ Scan238 | |
| Date | 20th May 1931 | |
| THE OBJECT OF MAKING THIS GRAPH IS TO GAIN AN APPROXIMATE IDEA OF THE ROAD WHEEL HP REQ'D FROM PHANTOM II TO ENABLE IT TO ACCOMPLISH A SPEED WITHIN THE NEIGHBOURHOOD OF 100 M.P.H. THE HP CURVE SHOWN IS A ROUGH CONTINUATION OF THE ONE GIVEN FOR 10 EX IN HS{Lord Ernest Hives - Chair}/RM{William Robotham - Chief Engineer}/LG 30-1-25, WHICH APPEARS TO INCREASE APPROXIMATELY AS (ROAD SPEED)^2.7 NEGLECTING ANY CONSTANTS DUE TO TRACTIVE RESISTANCE ETC. AT 100 BMEP & 3000 RPM THE HP OF THE 8 LITRE BENTLEY WOULD BE 184 & IF OUR GRAPH IS ANYWHERE NEAR RIGHT* THIS FIGURE IS LIKELY TO BE EXCEEDED SINCE THE CAR RUNS UP TO 99 MPH AT 3370 ENGINE REVS. * FOR THE BENTLEY 27 EX WAS FITTED WITH TWIN CARBURETTER & 5/1 COMPRESSION RATIO WHEN USED FOR THIS TEST. GEAR RATIOS :- 27 EX - 26.3 MPH @ 1000 RPM 8 LITRE BENTLEY - 29.3 MPH @ 1000 RPM Graph Labels: Y-AXIS: ROAD WHEEL HORSE POWER X-AXIS: ROAD SPEED M.P.H. CURVE 1: ROAD WHEEL HP 10 EX SEE HS{Lord Ernest Hives - Chair}/RM{William Robotham - Chief Engineer}/LG 30-1-25 CURVE 2: HORSE POWER REQ'D TO DRIVE CAR AREA BETWEEN CURVES: EXCESS HP AVAILABLE FOR ACCELERATION Annotations: 26 EX LAP SPEED 27 EX LAP SPEED 27 EX HALF MILE 6.5 LITRE BENTLEY LAP 6.5 LITRE BENTLEY 1/2 MILE 8 LITRE BENTLEY LAP 8 LITRE BENTLEY 1/2 MILE SEE TESTS REPORTED IN Hs{Lord Ernest Hives - Chair}1/MJ 17-4-31 | ||