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).
Calculation of air resistance coefficient and performance data for the Paulin Bentley.
| Identifier | ExFiles\Box 160\4\ scan0006 | |
| Date | 6th March 1939 | |
| 1379 1380 To By. {R.W. Bailey - Chief Engineer} c. to Ev. {Ivan Evernden - coachwork} c. to Da. {Bernard Day - Chassis Design} Rm {William Robotham - Chief Engineer} /TAC.3/JH.6.3.39. PAULIN BENTLEY WINDAGE. The following calculation for the "real value" of the air resistance coefficient K and hence for the H.P. required to lap a track at 80 M.P.H. has been made possible by obtaining accurate lap speeds, taking a road wheel dyno. curve and keeping a close watch on weights and tyres pressures. The frontal area by Ev. {Ivan Evernden - coachwork} was obtained by running a planimeter over a scaled frontal drawing, and rolling resistances are calculated on the Andreau formula. These figures represent all we know to date, and delete previous Paulin figures which at best were based on assumed powers and maximum speeds. Max. lap speed (Montlhery) ................... 110 M.P.H. B.H.P. at max. lap speed, corrected for power absorbed in driving the dyno. drums, and to 15°C since the car ran with an outside air intake ... 110 B.H.P. Frontal Area, A ............................ 21.65 sq.ft. Wt. of car on dyno. Total .................. 1.73 tons. Front .................. 0.75 tons. Rear ................... 0.98 tons. Wt. of car on road. Total .................. 1.70 tons. Front .................. 0.79 tons. Rear ................... 0.91 tons. Tyre pressures (road and dyno.) ............. 48 lb/in². Rolling resistance at 110 M.P.H., 48 lb/in² tyre press = ................................... 49.2 lb/ton. Rolling resistance at 80 M.P.H., 48 lb/in² tyre press = ................................... 29.4 " | ||