The lifespan testing of lamps under various voltage conditions and wiring configurations.
| Identifier | ExFiles\Box 167\1\ img263 | |
| Date | 10th June 1938 | |
| -2- Rm {William Robotham - Chief Engineer} /RC. {R. Childs} 7/JH.10.6.38. Group A. {Mr Adams} 1. 3.44 v. {VIENNA} 2. 3.66 v. {VIENNA} 3. 3.40 v. {VIENNA} After 8 hours 10 minutes running under these conditions, No. 3 lamp in C group burned out. It will be seen that this lamp was overloaded to the extent of from .15 to .22 volts, and at this had a very short life. In order to form a comparison, it was necessary to know the life of the lamps, when running at their normal voltage. For this purpose the remaining five lamps were connected in parallel, and the voltage adjusted to 3.5 volts. After 16 hours running under these conditions, making (16 plus 8 hrs. 10 mins) 24 hrs 10 mins in all, one lamps burned out. Readjusting the voltage to 3.5 the remainder of the lamps ran for one more hour, when two more failed. The lives of some of the lamps, were probably shortened through the lamps being over run at some time, as when in the series arrangement, and also for a very short time, when the first lamp failed in the parallel arrangement and the voltage had to be readjusted, but we can say that the life of this type of lamp running on its normal voltage is in the neighbourhood of 25 burning hours. In order to ascertain what extra service could be obtained by under - running them, a further test was made using six new lamps. These were connected in parallel and the voltage adjusted to 3.10 volts. Under these conditions the lamps ran successfully for 40 hours. The volts were then increased to 3.35 at which the lamps ran for a further 20 hours. At this point within a period of a few minutes, all six lamps were burnt out. During that time one lamp must have failed and the progress-ively increased voltage caused the others to fail rapidly in turn. As a matter of interest this point was checked when it was found that with six lamps in parallel removing one lamp, caused the voltage to rise from 3.5 to 4.22 volts. Summarising these results and adding our conclusion we arrive at the following - | ||
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).