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).
Calculations for vehicle horsepower, rolling resistance, windage, and potential lap speeds.
| Identifier | ExFiles\Box 160\4\ scan0007 | |
| Date | 6th March 1939 | |
| -2- Rm {William Robotham - Chief Engineer} /TAS. {T. Allan Swinden} 3/JH.6.3.39. Roll. Resist. at 62 m.p.h. [2nd. gear speed equivalent to 110 m.p.h. in direct] = ........ 25 lbs/ton. Hub H.P. = 110 + (0.98 x 25) 110 / 375 = 117.2 H.P. Since the road wheel dyno. power was obtained in 2nd. gear. H.P. absorbed by four wheels due to rolling resistance (on the road). = (1.70 x 49.2) 110 / 375 = 24.5 H.P. Hence H.P. remaining for windage = 117.2 - 24.5 = 92.7. This is equivalent to a resistance of 92.7 x 375 / 110 lbs. From which the real value of K = .00121 may be obtained. H.P. required to drive the car at 80 M.P.H. = [K.A. x 80³ + (0.7) x 29.4) 80] 1/375 = 40.7 H.P. Real K = .00121 (or Cx {Major Len W. Cox - Advertising Manager} = .473) H.P. required to drive the car at 80 M.P.H. = 40.7 (at road wheels) By working with "clutch horse powers" in the absence of "road wheel horsepowers", and using the hypothetical K which resulted, it was estimated that the Paulin Bentley would lap at 109½ on its recent run, whereas it actually lapped at 110. Working in the same way 160 clutch B.H.P. would give a lap speed of 115 M.P.H. and 165 H.P. would increase that lap speed to about 116½ M.P.H. Rm {William Robotham - Chief Engineer} /T.A.Swinden. | ||