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 late cutting in of 20/25 dynamos.
| Identifier | ExFiles\Box 60\4\ Scan150 | |
| Date | 20th April 1932 | |
| x6099 To PN.{Mr Northey} from Hs{Lord Ernest Hives - Chair}/Wst. To By.{R.W. Bailey - Chief Engineer} c. EP.{G. Eric Platford - Chief Quality Engineer} Mx.{John H Maddocks - Chief Proving Officer} Hs{Lord Ernest Hives - Chair}/Wst.4/AD20.4.32. LATE CUTTING IN OF 20/25 DYNAMOS. With reference to EP{G. Eric Platford - Chief Quality Engineer}'s and PN{Mr Northey}'s complaint regarding late cutting in of 20/25 dynamos, we have investigated the trouble and our remarks are as follows :- On one particular car in the Test Dept. a certain dynamo No. GHD, was found to cut in as follows. In the S & T and H S & T positions of the switch which, of course, short circuits the resistance unit, the dynamo cut in (hot) at 16 M.P.H. With the lamp switches off in the day position the dynamo cut in at 20 M.P.H. by the speedometer. This dynamo was thereupon removed from the chassis and tested on the bench. According to our figures of M.P.H. against engine R.P.M. this dynamo cut in on the bench at 13 M.P.H. (night) and 17 1/2 M.P.H. (day). From output results, dynamos of this type should not normally cut in later than 15 M.P.H. (night) and about 17 1/2 to 18 M.P.H. (day) so that it will be seen that this dynamo was quite O.K. to our specification. It was found on the heating test that the output of the machine was not as high as it might be, the full temperature rise not being obtained. As moving the control brush would tend to improve the cutting in point it is recommended that the production test dept. limits be closed in to 14 1/2 to 15 amperes, the machines falling below the limits being brought up by moving the control brush. It was also found that a field resistance unit borrowed from production was above the top limit in resistance. It was ascertained that most of these resistance units are on the high side, probably due to stretching of the wire in winding. We therefore recommend that the length of this wire be reduced by 2" - this, of course, will help the cutting in point. The inclusion in the production test of an open circuit voltage test with resistance in the field circuit as a check is also recommended. We feel that the effect of these recommendations will be to ensure that machines are up to standard. <del>rather than an improvement on the above figures</del> | ||