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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.
  
  


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