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 discussing the physics and design recommendations for using larger diameter bellows, referencing drawing number LEC.3835.
| Identifier | ExFiles\Box 4\1\ 01-page052 | |
| Date | 24th April 1934 guessed | |
| Messrs. Rolls-Royce Ltd. cessive. We are afraid that the only manner in which the duty can be performed satisfactorily would be the employment of a bellows having considerably greater area. You will appreciate that for a bellows having a given wall thickness, the stiffness depends both on the depth of convolution and on the circumference. The circumference increases in proportion to the diameter, whereas the area of the bellows goes up as the square of the diameter. Consequently, as the bellows diameter is increased the available load, which is the result of the product of the area and the pressure, goes up more rapidly than the stiffness of the bellows. There is, therefore, more power available with the large diameter bellows of given wall thickness and convolution depth than there is with a smaller diameter bellows having the same characteristics To make a satisfactory job, we would strongly recommend that some form of spring adjustment be incorporated so that the expanded position of the bellows at 75°C. can be adjusted to make up for slight variations in bellows stiffness and areas. This adjustment can, of course, be contained within the bellows unit, and once set can be sealed. The length of large diameter bellows required to give the same movement, would of course be very much smaller than that shown on your drawing. From examination of your Drg. No. LEC.3835, we note that the large diameter bellows would probably interfere with the setscrew which holds the float chamber in place. It would, therefore, be necessary for the increased diameter to occur below this point. Even then, we see no reason why the overall length should not be less than that shown on your drawing. Would you be good enough to give our remarks your consideration. We would take this opportunity of pointing out that there is extreme difficulty in obtaining an exact | ||