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 pump modifications for silence and performance, including diaphragm materials and stroke length.
| Identifier | ExFiles\Box 149\1\ scan0308 | |
| Date | 14th September 1936 | |
| -2- Hs{Lord Ernest Hives - Chair}/JBD.{John B. Dixon - Fuel Systems}11/KW.14.9.36. If, as you suggest, we rely solely on the clearance for silence, it would be advisable to remove the existing washers as we know they do not silence the pump, and the recess need not be so deep. With this arrangement we will be entirely dependent on the diaphragm material taking the blow when pumping vapour or priming, and it would need a long period of test to make certain this would not loosen the diaphragm on the spindle or that the material would stretch and the pump so become noisy. For the Bentley pump you are going to supply we suggest this is built up as recommended in this letter, using an armature with .025" deeper recess and standard stroke with .030" impact washer. We are definitely in a hurry for this pump and as it is only a question of obtaining recessed armatures it should not hold the pump up more than a day or two. If shims are not available in this case the brass distance pieces could be fitted to the required dimensions and only a short test at your Works of 2 hours or so would be sufficient as this pump is to be tested on a car. The above recommendations should help with the high lift pump, though as you state, stainless steel springs may be necessary. We are anxious not to shorten the stroke of the pump if it can be avoided, owing to the objections you raised, as though the material is stiffer when cold the danger of buzzing still exists when hot. The stiffness of the material may, however, be too much for the magnets on the full stroke, but this will be found out on test and the remedy would be increased loading rather than a sacrifice in the stroke and possible delivery. An increase of the minimum voltage to work the pump is not important as long as it remains below 9 volts. I should be glad to have some of the impact washers to test here in conjunction with your tests. Yours faithfully, FOR ROLLS-ROYCE LIMITED. | ||