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).
Continued analysis of dynamo output curves, comparing different models and operating conditions.
| Identifier | ExFiles\Box 182\M19\ img012 | |
| Date | 1st February 1931 | |
| -3- principle to too great a degree has led us into troubles in other ways. We now believe we can obtain a very similar result without the loss of cutting in speed, as has already been elsewhere explained, by introducing the additional reluctance at a point in the magnetic circuit where this introduction can be rendered an advantage in another way. The initial experiment on this principle is being urged through for trial. We can say in any case, that any modification which renders the output more sustained at speed will also have the effect of minimising the irregularities of output caused by irregularities in control brush bedding. So far we have been speaking of the relative shapes of output curves but it is also necessary to refer to the relative cutting in points and peak values of the output curves shown on Lec.2866 as those curves give an impression of superiority of Mr.Elliott's Lucas machine particularly in view of its size being nearly similar to that of our 20/25 dynamo. We do not know the revolutions per mile of this dynamo, but in the 20/25 case they are 4364 and in the Phantom case 3429, and it may be that the relatively early cutting in of the Lucas dynamo shown on Lec.2866 may be the result of a larger figure for the revolutions per mile. A point that L. will also have noted is that the cutting in on the low rate of charge is two miles per hour higher than on full rate. In regard to the peak outputs it will be remembered that if (a) The temperature of the carcase of the dynamo externally is less than 80°C. and (b) In the case of two of our curves which have been reproduced, the operating voltage is higher than 14.0 the output curves of our machines would be considerably higher than those reproduced. We have taken an actual curve on the E.60 dynamo loaned to us by FN. in similar circumstances to those in which we take our own curves, namely with a carcase temperature of 80°C. and constant operating voltage of 14.0. | ||