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 of determining the tractive resistance of a touring car at 60 M.P.H. and over.
| Identifier | ExFiles\Box 160\2\ scan0036 | |
| Date | 26th February 1923 | |
| 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/LG26. 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 v² 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. | MEASURED 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:- | ||