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).
Proposed tests to investigate dynamo failures, specifically relating to melting solder and faulty brush bedding.
| Identifier | ExFiles\Box 50\5\ Scan222 | |
| Date | 28th September 1923 | |
| EFC. X4333 BY10-P28.9.23. X 4333 DYNAMO TROUBLES. Referring to EFC1/T26923, I am of the opinion that it would have been better before replying to R11/M20923 to have carried out the set of tests I discussed with you on Monday last - the points that I raised I think are of distinct interest and value in regard to checking what are the conditions which definitely ensure reliability or otherwise. I certainly feel it is of the utmost importance for your department to try out the effect of extreme bedding in both directions on the brushes, treating the brushes singly and collectively in each case, the object of this test being to prove definitely whether it is possible by faulty bedding of an extreme condition to cause such a temperature rise on the Armature as would melt the solder, thereby causing failure of the system. If your test proved that the machine was definitely sensible to small variations in bedding to such an extent as to cause melting of the solder, then it is certain we would have to admit that the variations in the Works were the cause of the trouble, but it would also prove that we were running on a system which was so near to the danger point that at any time we were liable to slip over the edge into trouble, such a state of affairs would undoubtedly demand modifications in design. If extreme variations in brush bedding purposely produced did not result in melting out of the solder in the Armature connections, then the Works would have to be acquitted of being the cause of the failures which have taken place from time to time due to Armatures melting out. The further tests proposed were that the brushes should be removed in turn from the Commutator, starting with the most likely cause of the trouble and testing each combination to try out whether in each, and every case, such a state of affairs would result in melting the solder from the Armature. If faulty brush bedding would not do it and dismantling of the brushes would, then it would be clear that the trouble was caused either by a broken connection or a sticking brush, which might be due either to faulty workmanship or faulty design. The actual phenomena accompanying the failure in question would have to be relied upon who was to blame and whether such failures demanded improved design in order to avoid them, excepting under the most aggravated conditions of use which could not be justified on the ground of being even comparatively reasonable. contd. | ||