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).
The method for determining the tractive resistance of a touring car at 60 M.P.H. and over.
| Identifier | ExFiles\Box 73\3\ scan0369 | |
| Date | 26th February 1924 | |
| R.R. 493A (40 H) (SL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} EXPERIMENTAL REPORT. Expl. No. 4578 REF: Hs{Lord Ernest Hives - Chair}/R m/LC26.2.24. METHOD OF DETERMINING TRACTIVE RESISTANCE OF RR. TOURING CAR AT 60 M.P.H. AND OVER. Tractive resistance = a + b (V)^2 Where a.{Mr Adams} is the rolling resistance of the car and b V^2 is the increase in T.R. due to windage, v.{VIENNA} being some term directly proportional to the velocity and b. the factor of windage for the particular car being tested. At 5 m.p.h. we take the tractive resistance of the car to be independent of windage for practical purposes or a = T.R. of car at 5 m.p.h. Figures from 6.EX car graph 26.2.23. Tractive resistance = a + b (m.p.h. / 10)^2 where m.p.h. / 10 is the factor directly proportional to the velocity. | SPEED M.P.H. | MEAS-URED T.R. | VALUES OF a.{Mr Adams} | VALUE OF b(m.p.h/10)^2 T.R. - a | VALUE OF (M.P.H./10)^2 | THEREFORE VALUE OF b. FOR CAR IN QUESTION. | |--------------|----------------|--------------|------------------------------------|-----------------------|-------------------------------------------| | 5 | 23 | 23 | nil | --- | --- | | 10 | 26 | 23 | 3 | 1 | 3 | | 20 | 36 | 23 | 13 | 4 | 3.25 | | 30 | 52 | 23 | 29 | 9 | 3.22 | | 40 | 65 | 23 | 42 | 16 | 2.62 | | 50 | 110 | 23 | 87 | 25 | 3.45 | Average value 3.11 ∴ The factor of windage for a RR. touring car from our tractive resistance tests is 3.11 and the rolling factor 23 lbs/ton. contd:- | ||