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).
The porosity and leakage issues of S.U. petrol pump diaphragms, detailing results from endurance tests.
| Identifier | ExFiles\Box 149\4\ scan0230 | |
| Date | 8th April 1937 | |
| 1263 To Hs.{Lord Ernest Hives - Chair} from Rm{William Robotham - Chief Engineer}/JBD.{John B. Dixon - Fuel Systems} c.c. to Sg.{Arthur F. Sidgreaves - MD} Rm{William Robotham - Chief Engineer}/JBD.{John B. Dixon - Fuel Systems}1/AP.8.4.37 THE S.U. PETROL PUMP DIAPHRAGMS. We have had a few cases of the G.5. material becoming porous and causing leaks through the vents holes in the pump. When we were forced to take this material owing to the shrinkage of the G.1. diaphragm we were aware of the likelihood of them becoming porous, but in spite of this we accepted it on the results the S.U.Co. claimed to have had and more especially as it would not cause hold-ups on the road and at the same time it was the only alternative available. A month ago it was suggested that all diaphragms should be changed every 15,000 miles. We did not advise this as at the time we had no evidence that it was necessary, and any unnecessary dismantling and building up of petrol pumps leaves a chance for mistakes to be made. At the same time four double pumps have been running endurance on cold Ethyl petrol, four diaphragms having run 585 hours with no sign of porosity and four others 930 hours when they show very slight porosity. These tests were run on cold Ethyl petrol owing to the difficulty of maintaining hot petrol containing lighter fractions which distill off with the heat. The pumps were run at 10 gallons per hour for 700 hours and then reduced to four gallons per hour to increase the pressure and show up porosity. Thus to date they have pumped 5850 gallons each for one set and 7920 gallons each for the original set of two double pumps. The only involuntary stops have been due to the toggle mechanisms sticking after 700 hours due to wear and burning of the points, but these were not new at the start of the test. From these tests we were beginning to feel more confident of the material until:- (1) One side began to leak on 22.G.V. after 9900 miles. (2) Both sides leaking in London Trials Car 3.AZ.22. after 12,000 miles. (3) All three diaphragms leaking on 35-EX. which is fitted with the three pump scheme after 11280 miles. (4) Also three pumps returned from the Test Dept. (5) And six reported from Cricklewood. continued | ||