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 | ||