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).
Tests to determine the optimal brush and winding angles for an intermediate output S.S. Dynamo.
| Identifier | ExFiles\Box 60\1\ Scan125 | |
| Date | 23th September 1929 | |
| X6004 By.{R.W. Bailey - Chief Engineer} from EFC. c. Ry/RD. EFC1/AD23.9.29. 6004 X.8665. INTERMEDIATE OUTPUT S.S. DYNAMO. We have now completed careful tests with the three intermediate output S.S. armatures in standard S.S. carcases for the purpose of the determination of the best main brush angle (called the B angle), and suitable control brush angles (called C angle). The performance of this intermediate output armature has shown itself to be such that it will be possible to utilise this armature both as a high output armature (called the higher output), and as a normal output armature (called the lower output). For this purpose there will be one B angle which is the angle of retard of the centres of the main brushes with respect to the corresponding neutral no-load commutating points since the brushes are arranged on the pole centre line, this is also the angle between the pole centre lines and the neutral lines on the commutator. This angle has been fixed at 16° (i.e. rather greater than the approximate 10° we have previously adopted). Referring to our systematized method of giving the winding diagrams, there is for these 24 slot armatures, an angle which we call the M angle, which is the angle between the mica preceding marked commutator segment No.1 and the centre of the commutator end of the slot between two marked teeth. The sum of this angle and the B angle, called the N angle, is a function of the winding only and independent of the relative position of the commutator to the slots. This N angle was arrived at geometrically, and has been confirmed by actual tests to be 55.5°. The B angle originally proposed by us was 9°, consequently we gave 46.5° for the M angle. Actually a shop check of the M angle gave 45.25° (on two armatures), and a running check of the B angle gave 10.25°, the sum of these agreeing with the 55.5 determined geometrically. Now we require a B angle of 16° and therefore we require an M angle of 39.5°. We should be pleased if you would now arrange for the instruction of three further armatures with M angles of 39.5° as above. We have standard S.S. carcases in which these armatures can be put to make finally complete experimental intermediate output S.S. machines | ||