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).
Technical assessment of a Type A Dynamo, detailing its electrical performance and manufacturing quality.
| Identifier | ExFiles\Box 3\5\ 05-page067 | |
| Date | 19th May 1919 guessed | |
| To Messrs. S. Smith & Sons. .2. EFC1/T. Contd. DYNAMO - TYPE A.{Mr Adams} The corresponding figures for the larger dynamo we find to be 500 R.P.M. for 12.4 volts (cold) and 565 R.P.M. for 13.6 volts in the hot condition, after running on load. After this point we find that the current delivered to the battery rises very rapidly (especially in the cold condition) and in either case more rapidly in relation to full out-put than in any other constant current system of control we have tried; and attains a value of nearly 13 1/2 amperes at 1500 R.P.M. after which it falls steadily to about 11.7 amperes at 3500 R.P.M. In the cold condition, a maximum current of 14 1/2 amperes is attained at about 1500 R.P.M. falling off to about 14 amperes at 3500 R.P.M. Electrically these results are undoubtedly very good, there being the great advantage in this dynamo over others we have tried, in that, for the same out-put at high speeds there is a much more abundant out-put of current at speeds below about 1600. This, of course is a very desirable thing for town work. We will let you have later on, copies of curves from which these figures are taken. Electrically we are convinced that, of all constant current armature re-action systems of control, by this method you get results of highest value in relation to the additional complication, as compared with an ordinary shunt wound machine. We agree with you that the armature heating for the same out-put is probably less in this type of control than in the others, other things being the same, but certainly not to the full extent as compared with an ordinary shunt wound machine, as it may be shown that in the simple third brush scheme with a control winding on the field poles, the main portion of the armature current is confined to a certain section of the armature in very much the same way. We noticed that the sparking at high speeds on this machine was rather bad on the auxiliary brushes. We have indicated to you that your equipment satisfies our electric requirements, but unfortunately we have not had an opportunity of judging the general manufacturing excellence of your production articles. We appreciate that the first machines submitted to us were hand made, and therefore not representative and we would like to arrange for the writer to visit your works for the purpose of inspecting some of your standard production, as soon as you have reached a normal production stage, perhaps you will write to us regarding convenient days. For your guidance we would inform you that we require a considerable advance as regards the quality of finish of the whole machine, but apart from this point the type "A" dynamo is very close to our requirements. Considerations of chassis delivery dates have compelled us to fix our policy regarding the first series to the exclusion of your out-fit. We have written you at some length on this matter, as it is our desire to provide all the technical assistance possible, in the belief that only by the closest technical co-operation can this class of equipment be perfected. We shall be glad, therefore, if you will consider these and any other reports which | ||