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).
Use of bonnet shutters versus louvres, focusing on noise, cooling, and cost.
| Identifier | ExFiles\Box 66\3\ scan0175 | |
| Date | 1st June 1927 | |
| To Hs.{Lord Ernest Hives - Chair} from BJ. using shutters fore and aft on bonnets of cars going to hot countries, as there are two strong points from practical experience we have found against using louvres, namely, that they do very considerably increase the noise that one can hear from the engine running; also that even in hot countries there are periods of cool weather when it is advantageous to be able to keep the bonnet closed, especially as cars are not always used at the same altitude but sometimes are taken to hilly or mountainous districts where the temperature is much lower. The actual difference in water temperature obtained by the use of louvres as compared with shutters is extremely small, being a difference we believe that with bonnet shutters all open boiling point is reached at an atmospheric temperature of 26.5.C. = 79.F., as compared with a louvred bonnet of 27.C. = 80.F. In any case on cars going to hot countries there should be no objection to placing a small plate near the thermometer or radiator shutter regulator, indicating that, if the water overheats, the bonnet shutters should be opened. We should be glad if the Works would give their very special attention to considering how far the cost of fitting shutters to bonnets can be reduced, either by a more simple design or possibly cheaper method of manufacture. The present cost is £13.12 per bonnet for the 4 shutters, which appears to us to be excessive. There is another point which H.{Arthur M. Hanbury - Head Complaints} has mentioned - we shall have to keep it in mind seriously - namely, that he has cured many complaints of floorboards overheating by advising customers to open their bonnet shutters, and this again must be taken into consideration at the time we make our tests in August. In regard to the 20 HP, we should like to consider carefully the desirability of fitting shutters in the bonnets in place of louvres for the reasons mentioned above, namely: 1. Noise. 2. Being able to open or shut them according to temperature. 3. Cost. | ||