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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).
Criticizing braking figures and curves published in 'The Motor' magazine.

Identifier  ExFiles\Box 23\4\  Scan057
Date  23th March 1925
  
R.R. 493a (Sht) (D.B. 175 25-9-24) J.H.D.

EXPERIMENTAL REPORT. -3- Expl. No. REF:Ha/Aml/LG23.3.25.

Underneath the curve in 'The Motor' the following sentence is found:-

" GRAPH SHEWING THE GOOD BRAKING FIGURES OBTAINED ".

We cannot ourselves imagine a more inconsistent set of brakes than one whose efficiency varies in this manner, so that even were the curve correct, the remark of the journal is most misleading.

Finally, a large number of the curves in 'The Motor' purport to give both the time and distance to rest from any road speed. On any normal car, once the brakes have been applied to obtain maximum effect the retardation of the car is uniform unless the road surface varies enormously, say from concrete to wet macadam.

If an inferior brake lining is employed, it is just possible that towards the end of a stop from 60 m.p.h., the brakes might lose some of their grip due to heat but most unlikely at the lower speeds.

As all the tests we reproduce were carried out on dry concrete, we may take it that for pull ups from 40 m.p.h. and below the retardation should be uniform.

Therefore for any given distance to rest there is a definite time which should be taken and can be easily calculated mathematically.

'The Motor' representative is aware that the time to rest should be proportional to the speed from which the pull-up is made, and so he measures his distances and plots them out in
  
  


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