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 investigation procedure for a 20 HP dynamo armature, focusing on commutator testing and soldering methods.
| Identifier | ExFiles\Box 47\4\ Scan178 | |
| Date | 2nd May 1924 | |
| To NHC. from EFC. c. to EY. c. to WOR.{Arthur Wormald - General Works Manager} X.4383 - 20 HP. DYNAMO ARMATURE EX CHASSIS 48-G-4. Herewith the above armature. Will you kindly in this case (and in future similar cases) first have the armature commutator connections released and return the armature to us for commutator drop test. After this test we will again hand you the armature to have the commutator connections resoldered, which re-soldering should be carried out with the necessary care to prevent metallic solder connections between commutator bars, a satisfactory drop test to avoid this not being possible owing to the condition of the commutator being left as received. We wish to make it clear that, in the cases of these customers' dynamos which are sent to us by EY. for investigation, when we ask you for the commutator connections to be resoldered we only want the electrical connection between the armature wires and commutator segments making sound, and no actual clearing out of the slots between the segments, such as would make the commutator satisfactorily pass a drop test. The reason for this is naturally that we want to investigate the dynamo in the condition which rendered the flowing of the solder possible, namely in the condition in which the commutator segments are possibly partly short circuited, the actual flowing of the solder being looked upon as a resultant effect and not the initial cause of the trouble. Then we can say to Production, if we prove such to be the case, that the cause of the failure is that the commutator was undercut by the old method (which has now, on our recommendation, been considerably improved upon), because we have examples of dynamos which have been machine undercut in the Expl. Dept., the condition of whose commutators is as good as any we know. In passing, I am anxious to show Mr. Bailey the condition of these commutators, which have done approximately 2,500 and 5,500 miles respectively, because it is understood that the method in use on production for undercutting the commutator is still not the best, as exemplified in the Bosch and Scintilla machines. Contd. | ||