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).
Unsatisfactory late cutting-in performance of 20/25 HP dynamos.
| Identifier | ExFiles\Box 60\4\ Scan153 | |
| Date | 26th April 1932 | |
| WST See me Tho 26/4/32 16099 PN.{Mr Northey}1/WT23.4.32. S/W. Hs{Lord Ernest Hives - Chair}/Wst. Copy to Sg.{Arthur F. Sidgreaves - MD} By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair} EP.{G. Eric Platford - Chief Quality Engineer} Mx.{John H Maddocks - Chief Proving Officer} H.{Arthur M. Hanbury - Head Complaints} Late cutting-in of 20/25 H.P. Dynamos. In reply to your Hs{Lord Ernest Hives - Chair}/Wst4/AD20.4.32 it would appear from the tests made by you of the Dynamo No. GHD referred to that the installation on the car confirms the unsatisfactory cutting-in which was brought to your notice by me, and discussed with EP{G. Eric Platford - Chief Quality Engineer}, the night position, not cutting-in until 16 m.p.h. instead of 13, and the day position, not cutting-in until 20 m.p.h. instead of 16 as indicated in your curves of performance. Your bench-test you say showed that this dynamo was O.K. to your specification. I do not understand this after your previous remark that its daylight cutting-in was between 17½ to 18 m.p.h. instead of 16. I have made a further careful test on our London Trials car GBT-24 (this is not the car previously referred to by me when at W) and it is found that while the daylight cutting-in occurs at 18 m.p.h., no battery charge commences until 20 m.p.h. whilst the maximum charge occurs at 32 m.p.h. The night position cuts in at as low as 12 m.p.h. and at 18 m.p.h. the output of the dynamo balances the load with all lamps on. It is quite obvious that cars fitted with generators giving these figures will gradually discharge their batteries running about town all the time at speeds under 20 m.p.h. This of course is entirely unsatisfactory. The already sufficiently bad position with regard to cutting-in has been, I understand from your memo, accentuated by the fact that the resistance units have been graded too high in resistance, and you propose to shorten these units by 2" because you suggest the section of the wire has been reduced by stretching. It is difficult to believe that with reasonable care any appreciable stretching need take place. I shall be glad to know what is the gauge material and length of wire on these units and the desired ohmic resistance. Your proposal to improve the cutting-in time and output by a further adjustment of the control brush would appear to be a wise one. I should like to know by the time these various points have been attended to what will be the cutting-in speed on standard cars, and at what additional speed a charging current of say 3 amps. is being given to the battery in daylight. PN.{Mr Northey} | ||