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).
Investigation into the failure of the 'B' side of a 2.B.50 petrol pump.
| Identifier | ExFiles\Box 112\3\ scan0037 | |
| Date | 30th December 1940 | |
| To Rm.{William Robotham - Chief Engineer} from Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby} Copy to Rm{William Robotham - Chief Engineer}/Wym.{G. Harold Whyman - Experimental Manager} 2.B.50 - PETROL PUMP FAILURE OF "B" SIDE With reference to Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby}7/ET.13.12.40, it was mentioned that the only important difference in the condition of the two sides was the fact that, on "B" side, the contacts were pitted worse than on "A" side and, in the former case, there was some soot present. This condition was at the time excused by reason of the probably large mileage run by the pump on 28.G.VII and 2.B.50. It was later decided to go deeper into the question of exactly why "B" side failed while "A" side continued to work. The pump was therefore rigged up in the laboratory, to pump paraffin. It was found that, whereas "A" side would work on about 9 volts, "B" side would not work under 12 volts, and then only because, by dismantling the pump, we had freed the rollers &c. "B" side was then taken down and the rollers and their races cleaned and packed with grease. It was found that the pump would now work as low as 8 volts, a standard test which should be passed by all pumps. The contact points were then cleaned up, and this appeared to give a further slight improvement in the actuation although the minimum working voltage was not lowered. The toggling action of "B" side had been sluggish all along, and there was also some bouncing of the contacts, both of which conditions were confirmed by the Cathode Ray Oscillograph. This might either be due to an outer contact spring which was too strong or a weak toggle spring. The former springs were inter-changed on "A" and "B" sides, with no apparent advantage, but on changing round the toggle springs, it was found that "B" side now worked well, but "A" side would hardly work at all. On examining these toggle springs, it was found that the good one was slightly larger than the bad one, and that the large one was similar to those fitted on present production pumps. It therefore seems likely that the contacts on "B" side were at the best of times bouncing as they closed and staying on longer than they should, giving the current more time to build up and causing a bigger arc. This arcing being far more serious on "B" side for the above reasons, the formation of the black non-conducting tungsten oxide was accelerated, giving poor contact, and when the rollers began to stick and the mechanism to get stiff generally, it was "B" side that failed first due to the toggle spring being too weak to deal with the overload. Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby} | ||