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).
Performance variations, modifications, and testing for 20 HP and 40/50 HP dynamos.
| Identifier | ExFiles\Box 165\6\ img139 | |
| Date | 29th March 1927 | |
| X.5660 To EY. from EFC. c. MX.{John H Maddocks - Chief Proving Officer} F c. Mr. Brock. EFCL/T29.3.27. 20 HP. DYNAMO. Referring to the fifth paragraph of EY6/H25.3.27, and the second par. of EY7/H23.3.27, we have never expected to get an output curve with the modified machines to satisfy even approximately our specified output, and those machines we have passed have been passed to an inferior standard. One of the difficulties with these single modification machines is the big variation from one machine to another. The first one of each of the 40/50 and 20 HP. machines which we tried happened to be unduly large in output, and that was why we called for the second modification in each case. The other one or two machines we have received have not been so large in output and that is why we have been able to pass them. It is necessary therefore to examine several of these machines before we can fix up a reasonable standard to which we can pass them, and you may depend that in doing so we will make this include as many machines as is reasonably possible. The thing that we do not think is right is for these machines to have an excessive peak output as some of them have, as in such a case it would also interfere with heating and commutation, and would not realise the advantages over the standard machine to which you refer in EY7/H23.3.27. Concerning these, from what we have seen of single modification machines so far, we should not say that a/- and d/- are necessarily the case if the output happens to be rather high, though I agree that a/- would be the case on the average, and probably also that the average machine would just satisfy d/-. One good reason for the cooler running is the fact that the peak output of the machine is at a higher speed than in the standard case, and there is therefore more windage. In regard to b/- and c/-, we are of the opinion from what we have seen so far that there is not much difference, but will refer to the matter again when we have had more opportunity of running the machines comparatively with the standard. We will as soon as possible issue a specification of inspection and test for both 20 HP. and 40/50 HP. machines with single modification, but in order to get this reasonably right it is first necessary for us to examine the performance of one or two machines of each kind. We take it from your remarks concerning the 28 slot armatures that you are taking steps to obtain Wor{Arthur Wormald - General Works Manager}'s approval. As we have been promised two more 28 slot 20 HP. armatures for to-day, perhaps it would now be as well not actually to put anything in hand until we have had the | ||