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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).
Page detailing the methodology for calculating air drag from dynamometer horsepower figures and test results.

Identifier  ExFiles\Box 161\1\  scan0219
Date  10th September 1938 guessed
  
-2-

It would be inadvisable, however, to
judge from one isolated case.

In calculating these values of K it has
been assumed that dynamometer horse power figures
given for the various speeds have been those available
after subtracting the rolling resistance for the rear
axle weight, i.e. for each particular speed and horse
power the corresponding tractive effort is calculated
and from this the rolling resistance of the front
wheels only is subtracted to obtain the air drag
figure.

For the three throttle stop positions
of 28-G-VI. the lap speeds given were 50, 65 and 73
m.p.h. and the corresponding dynamometer horse powers
were 26.2, 42.6, and 59.2. Increase of weight from
41 1/2 to 51 1/4 cwt reduced lap speed from 73 to 71.4 m.p.h.

Da{Bernard Day - Chassis Design}/DB.{Donald Bastow - Suspensions}
  
  


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