Rolls-Royce Archives
         « Prev  Box Series  Next »        

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).
Comparison of English and French formulas for calculating vehicle rolling resistance and dynamics.

Identifier  ExFiles\Box 161\1\  scan0221
Date  10th September 1938 guessed
  
2

CONVERTING FOR THE DIFFERENT UNITS THE CORRESPONDING
ENGLISH FORMULA BECOMES:-

RT = (1 / P^.64) * [ 245.6 + (V^3.7 / (397 * P^1.44)) ]

WHERE RT = ROLLING RESISTANCE, LBS/TON
P = TYRE INFLATION PRESSURE, LBS/IN^2
AND V = SPEED IN M.P.H.

METHOD OF FINDING Cx{Major Len W. Cox - Advertising Manager} OR K
FRENCH FORMULA:-

FOR A VEHICLE OF WEIGHT P KG. THE
TIME FOR A SPEED DECREASE, IN NEUTRAL, FROM V1 TO V2
METRES/SEC IS t SEC, AND THE MAXIMUM CROSS SECTIONAL
AREA IS S SQ. METRES. THEN IF φ IS THE ROLLING
RESISTANCE IN Kg/TONNE,

Cx{Major Len W. Cox - Advertising Manager} = (P / (62.6 * V1 * V2 * S)) * [ (101.6 * (V1 - V2) / t) - φ ]

THE EQUIVALENT ENGLISH FORMULA BECOMES:-

K = (W / (2255 * V1 * V2 * A)) * [ (101.7 * (V1 - V2) / t) - RT ]

WHERE W = VEHICLE WEIGHT IN LBS, V1 AND V2 ARE SPEEDS IN M.P.H.,
t IS THE TIME IN SECS AND RT = ROLLING RESISTANCE LBS/TON
  
  


Copyright Sustain 2025, All Rights Reserved.    whatever is rightly done, however humble, is noble
An unhandled error has occurred. Reload 🗙