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).
Acceleration tests comparing single and double hot spot feeds to address 'flat spot' issues, with notes on air silencer and wing design.
| Identifier | ExFiles\Box 155\1\ scan0084 | |
| Date | 17th May 1933 | |
| -2- Hs{Lord Ernest Hives - Chair}/Lid.{A. J. Lidsey}1/KT.17.5.33. With regard to the air silencer loss of 1.05 m.p.h., the final air silencer to be fitted for production will not absorb any power, and this loss therefore will not occur. The loss due to the twin hot spot feed was expected as we know that the increased heat given by the two port feed is, however, not good enough to overcome "flat spots" at lower speeds. We are hoping to achieve a compromise by using the twin hot spot feed but with the heat restricted to a point where it is just sufficient to overcome "flat spot" troubles. The front wings account for the same loss as the domed type of front wing on the first Bentley car. We were hoping the flared wings would be better. The flared wings on this car are unnecessarily large and high, and we hope to improve them on the next Bentley car (3.B.IV), by lowering them and reducing them in size slightly; we also improve the appearance by making the alteration. Acceleration tests were made as follows :- | M.P.H. | Single Hot Spot Feed. | Double Hot Spot Feed. | | :--- | :--- | :--- | | 10 - 30 | 8.7 secs. | 9.2 secs. | | 10 - 50 | 17.4 " | 18.9 " | | 10 - 60 | 24.4 " | 24.9 " | | 10 - 70 | 33.3 " | 34.2 " | | 60 - 70 | 8.8 " | - | | 60 - 75 | 15.2 " | 15.4 " | The apparent improved performance when using the single hot spot feed is rather inexplicable, because the engine was in such a hot condition (having been lapping the track for some considerable time in each case before the readings were taken), that the type of hot spot feed could scarcely be expected to make any difference. There is one point that may explain it, the figures for the double hot spot were taken early in the day, those for the single were taken later in the day, and during the interval the car had covered something like 100 miles at full speed on the track and had conceivably become freer. | ||