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).
Letter from the Experimental Department discussing the design and necessity of a stabilising bumper bar.
| Identifier | ExFiles\Box 89\1\ scan0132 | |
| Date | 25th January 1935 | |
| <7961a Exptl. Dept. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}3/KW. 25th January, 1935. R.{Sir Henry Royce} Summers, Esq., Messrs. John Summers & Sons, Ltd., Hawarden Bridge Steel Works, Shotton, Chester. Dear Dick, Thank you for your letter of the 23rd. I was in London on Wednesday and hoped to try your car but it was not finished. The cure for front wing flap which has been fitted to this car is the Stabilising Bumper Bar. At first sight you may be inclined to say that this is not a good way of accomplishing the result. Actually, after putting in a lot of hard work on the job for about 12 months, I have come to the conclusion it is really a scientific solution. The point is that to build a frame with such a high frequency that it would not respond to any excitation due to the wheels hitting irregularities in the road surface means an immensely massive structure. The bumper bar eliminates the resonant period because it is tuned to that particular frequency. You will of course try the car with and without this bumper bar, as I also should under the same conditions. You will find that the bumper bar weighs about 30 lbs. I regret this weight addition to the chassis as much as you do. I have, however, come to the conclusion that with 4,000 new motor cars going on the road every week, bumper bars will become essential during the next 12 months. The lightest non-stabilising bumper bar that I can get weighs about 20 lbs. I therefore feel that I have eliminated your wing flap and in effect only added 10 lbs. ultimate weight to the car. I should have to have added several times this amount to get the result by stiffening the frame. | ||