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).
Minor corrections for a small dynamo with a 36-slot armature following examination and tests.
| Identifier | ExFiles\Box 168a\3\ img102 | |
| Date | 6th July 1938 | |
| To By/RD. from RM{William Robotham - Chief Engineer}/RC.{R. Childs} c. By.{R.W. Bailey - Chief Engineer} 8 6142 Rm{William Robotham - Chief Engineer}/RC.{R. Childs}5/WH.6.7.38. RE SMALL DYNAMO WITH 36 SLOT ARMATURE. As a result of our examination and tests on both the experimental machine and the first complete production machine of the new type, we find that there are a few minor points that need correction. These are as follows:-- (1) It was found that the angle of retard of the brushes was 13° instead of the intended 8°. It has been confirmed on the experimental machine by lifting the coil end connections and moving them one segment (equals 5°) round the commutator, that 8° is the better, and correct angle. (2) The brush holder springs should exert a pressure on the top of the brush, of from 15 - 18 ozs. Actually the spring pressure was found to be only 12 1/2 to 13 1/2 ozs. This also applies to the springs on the new brush-gear of the large machine of similar type. (3) It was found that the clearance between brush and holder was in some cases only .002". We have always maintained that with this design of brush-holder relatively large clearances are permissible. We feel, in view of the fact that we still have trouble from sticking brushes, that advantage should be taken of this, and the clearance be made not less than .008". We should say that this clearance should not be obtained by reducing the thickness of the brush much below its present value of .300" on account of overloading the brush. This applies to the large machine as well. (4) It was observed on the first complete machine that the two terminals were different in respect of the rotational position of the cable opening at the top of the terminal. One appears to be wrongly twisted round. RM{William Robotham - Chief Engineer}/RC.{R. Childs} | ||