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 149\3\ scan0171 | |
| Date | 27th December 1940 | |
| To: Rm{William Robotham - Chief Engineer} from Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby} c. 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 there that the only important difference in the condition of the two sides was the fact that in "B" side the embacts 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.GVI and 2.B.50. It was later decided to go more deeply 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 first dismantling the pump we had freed the rollers etc. "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 taggling 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 Oscillagraph. This might either be due to an outer contact spring which was too strong or a meak taggle spring. The former springs were interchanged on "A" and "B" sides with no apparent advantage, but on changing round the taggle springs, it was found that "B" side now worked well, but "A" side would hardly work at all. On examining these taggle springs it was found that the good one was slightly larger than the bad one, and that the larger one was similar to those fitted on present production pumps. It therefore seems likely that the embacts 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 taggle spring being too weak to deal with the overload. Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby} | ||