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).
Test report comparing the cooling performance of different radiator matrix and shutter grille designs.
| Identifier | ExFiles\Box 82\5\ scan0021 | |
| Date | 4th March 1937 | |
| -2- Mk.Vl.{V. Lewis / Mr Valentine} lightened construction matrix shows a gain in cooling over the standard 58 MM. Mk.V. - approximately 9% at both low and high speeds. (4) From tests 8, 9 and 10 it is seen that the present standard Bentley appears to have little spare cooling margin with the standard 58 M.M. Mk.V. matrix at low speeds. Actually the difference in critical air temperature between 30 M.P.H. and 90 M.P.H. (approx) is greater than we would have expected from previous test figures and we would point out as in the case of the Phantom III. that these low speed full throttle conditions represent a condition which would rarely, if ever, be encountered under road conditions, and that therefore it is probably permissible to have a low speed critical air temperature as much as 5 or 7° degrees C. below the minimum desirable maximum speed critical air temp. We propose, however, to re-check the cooling on the standard Bentley at Brooklands as soon as possible. Summary. The dummy shutter grille as made up at the moment, even when used with the 52 MM. Mk.Vl.{V. Lewis / Mr Valentine} type matrix reduces the cooling of the Bentley car to a standard blow that of the present production car. In order to remedy this it will be necessary either to open the dummy shutters somewhat or to use a deeper matrix. As soon as Brooklands track opens (approx. in one week's time) we propose to determine the minimum angle of opening of our standard shutters to give adequate cooling with - (1) a 52 MM. Mk.Vl.{V. Lewis / Mr Valentine} matrix. (2) a 58 MM. Mk.Vl.{V. Lewis / Mr Valentine} matrix. We shall then judge whether the appearance is still acceptable and if so have a second grille made up to give this angle of opening. Meanwhile, the present grille fitted to 3.B.lV. car will remain in France to complete 15,000 miles in order to tests its mechanical strength, etc. and the 52.MM. Mk.Vl.{V. Lewis / Mr Valentine} matrix will be standardised as soon as the car completes 15,000 miles (this matrix besides giving increased cooling, saves approximately 7 lbs. in weight and costs 6d. less than the standard article.) Examination of the test figures indicates that the engine water flow could be increased with advantage thus raising the critical air temperature an appreciable amount. Rm{William Robotham - Chief Engineer}/Std. | ||