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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).
Timed lap performance tests comparing different axle configurations, cut-out settings, and body windage.

Identifier  ExFiles\Box 29\3\  Scan321
Date  4th June 1931
  
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Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}1/KT.4.6.31.

We then ran the cars side by side up to maximum speed from about 60 MPH. 26-EX did not appear to show any superiority until over 70 MPH. At maximum speed there was not more than 2 MPH. difference between the two cars. We then repeated the timed laps on 26-EX the results of which were as follows :-

Lap Speed. 26-EX.

C.O. closed 2 min 3.4/5 secs. 80.46 MPH.
C.O. open 1 min 58.75 secs. 84 MPH.

It will be observed that the higher geared axle has increased the speed by 3½ MPH. with the cut-out closed, and 1½ MPH. with the cut-out open.

Besides comparing the two axles these tests shewed what we already know, that the windage of our Sports cars is not appreciably less than our standard cars. Our original sports type wings on 10-EX. certainly gave us a slight increase in speed of 1½ MPH. and we propose to make tests to see whether the sports wings, as now being made, have become less efficient for windage.

With regard to the rear of the car. We know that this is a most important feature when trying to improve the stream-line shape of a body, as we gained 2½ MPH. with a tail on an open touring car (10-EX.) However, unless we know what type of stream-lined rear end to the car would be acceptable to males, it is rather difficult to know where to begin usefully with such experiments.

We saw a most attractive looking 8 litre Bentley with a tail, that Jack Barclay had sold, but it was on a 2 seater car and very badly designed for accessibility.

It is interesting to note that these recent figures approximately confirm our previous results on axle ratios - i.e. 8.9.27. where we got 1.5 MPH. from a 6% higher axle with a low windage body, and 15.6.30 where we found the difference between a 15 and 16 tooth axle was about the same order.

P.N. drove the car in London traffic in addition to the tests on Brooklands.
  
  


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