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).
Extract detailing French and English formulas for calculating vehicle air resistance and rolling resistance.
| Identifier | ExFiles\Box 161\1\ scan0220 | |
| Date | 10th September 1938 | |
| I. PERFORMANCE. [EXTRACTED FROM 'L'AERODYNAMIQUE APPLIQUÉE À L'AUTOMOBILE' BY J.{Mr Johnson W.M.} ANDREAU. 'LAVIE AUTOMOBILE' 10.9.38] AIR RESISTANCE FRENCH FORMULA IS:- Rx = Cx{Major Len W. Cox - Advertising Manager} S V²/16 WHERE Rx = AIR RESISTANCE, KG. Cx{Major Len W. Cox - Advertising Manager} = AIR RESISTANCE COEFFICIENT S = CROSS SECTIONAL AREA SQ METRS V = SPEED IN METRES/SEC ENGLISH FORMULA IS:- RA = K A V² WHERE RA = AIR RESISTANCE, LBS. K = AIR RESISTANCE COEFFICIENT A = CROSS SECTIONAL AREA, SQ FEET. V = SPEED IN M.P.H. BY SUBSTITUTING FOR THE DIFFERENT UNITS, WE FIND THAT Cx{Major Len W. Cox - Advertising Manager} = 391 K.{Mr Kilner} PRESENT NORMAL CARS HAVE Cx{Major Len W. Cox - Advertising Manager} = 0.6 TO 0.7 [K = .00153 - .00179] STREAMLINED COACHWORK ON SAME CHASSIS, Cx{Major Len W. Cox - Advertising Manager} = 0.2 TO 0.25 [K = .00051 - .00064] [INCREASE IN SPEED OF 20-25 %] WHERE COMPONENT DISPOSITION AND CAR LAYOUT CAN BE MODIFIED TO SUIT REQUIRED OUTLINE, Cx{Major Len W. Cox - Advertising Manager} = 0.15 TO 0.07 [K = .000384 TO .000179] MINIMUM FOR BODY IN AIR IS Cx{Major Len W. Cox - Advertising Manager} = 0.05 [K = .000128] ROLLING RESISTANCE. FROM RESEARCHES CONDUCTED BY THE 'SOCIÉTÉ CONTINENTALE' φ = (1 / p^0.64) * [20 + (V^3.7 / (1,294,000 * p^1.44))] WHERE φ = ROLLING RESISTANCE, KG/TONNE, p = INFLATION PRESSURE COLD [15°C.] IN KG/CM² V = SPEED IN KM/HOUR. | ||