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 comparing road wheel horsepower versus engine RPM for various motor cars.
| Identifier | ExFiles\Box 125\3\ scan0098 | |
| Date | 14th March 1939 | |
| ROAD WHEEL HP COMPARISON DYNO HP AT ROAD WHEELS ALL CURVES CORRECTED TO 50°C AIR TEMP, 45 Lbs/in² TYRE PRESS. AND FOR HP REQD TO DRIVE THE DYNO. HUB H.P. i.e. DYNO HP + HP DUE TO THE ROLLING RESISTANCE OF THE REAR WHEELS. B.H.P. ENGINE R.P.M. AT 60 M.P.H. BUICK 2800 HUMBER 3000 WRAITH 2900 BENTLEY II 2900 ENGINE R.P.M. BUICK CENTURY 1939 BUICK BENTLEY II - 6 BM BENTLEY II WRAITH - 27 G.M. HUMBER SUPER SNIPE WRAITH HUMBER Rm{William Robotham - Chief Engineer}/Swinden/14.3.39 | ||