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).
Issues with S.U. petrol pump diaphragm materials, including shrinkage and reactions to alcohol fuels.
| Identifier | ExFiles\Box 149\1\ scan0323 | |
| Date | 16th September 1936 | |
| To Hs.{Lord Ernest Hives - Chair} File Copy to G.W.H. The Diaphragms in the S.U. Petrol Pump. Following my visit with Mr. Hancock to the S.U. Company, when they agreed with us about the shrinkage of the seaweed base material we now use, and recommended us to change over to the G.3. zinc type material they fit as standard. I saw them yesterday and tried to ascertain all possible faults with this material and what was the position with regard to supplying it. This material has been in use for 18 months and in over 200,000 pumps supplied, the diaphragm failures have been less than 1% of the total. Morris Motors continued to use the gut material we had turned down for 12 months until they had got experience of the G.3. and are now fitting it as supplies become available. They have recently had the first failure of a diaphragm using Cleveland Discol, but this may be an isolated case as their own car has run for 12 months on this fuel without trouble. I also made enquiries about the A.C. mechanical pump diaphragm: this they have tried and found it will not stand alcohol fuels and is inclined to disintegrate slowly with petrol. The alcohol fuels contain Pyridine, and it is this substance which attacks the diaphragms. It removes the dressing on the A.C. and to a lesser extent on the G.3. material, whereas it only slightly hardens the seaweed base material, but in this case the alcohol dehydrates and shrinks it. Thus, of all the materials now in use, the G.3. which has already had 18 months in service with little trouble appears the most satisfactory, and as yet there is no diaphragm which has been definitely proved to withstand alcohol for a long period. Lp{Mr Lappin}'s car is at present fitted with G.3 diaphragms and is to run on Discol. Just at the present time the S.U. Company are having difficulty in obtaining cloth of the required thickness and quality which they have proved good to be sent to Germany for treatment. To-day they inform us they will have suitable diaphragms available in a month, and advise us to wait until then before changing over. This we have agreed to do, and in the meantime the seaweed base diaphragms are to be raised to a higher temperature before assembly to minimise the risk of shrinkage and consequent failure in service. Hs{Lord Ernest Hives - Chair}/J.B.Dixon. | ||