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).
Results of bench tests on a modified Phantom III Starter Push button Switch.
| Identifier | ExFiles\Box 168a\2\ img332 | |
| Date | 23th December 1937 | |
| To by.{R.W. Bailey - Chief Engineer} c. to by/RD. 6139 RM{William Robotham - Chief Engineer}/NO.2/JH.23.12.37. re Phantom III Starter Push button Switch to R.R.Sch.NO.1. We have now completed bench tests on the above, in which a modification is introduced to improve the connections to the carbon contacts. The switch was wired up to control current of 18 amperes passing through a standard teazer winding and a standard main switch relay coil. Using a 12 volt supply the switch was made to operate at a rate of 10 times per minute, 3 seconds 'on' and 3 seconds 'off'. The switch worked perfectly for 12,000 operations, after which a slight spark was discernible on the 'break'. The switch was dismantled and the contacts re-adjusted after 15,000 operations. The same fault occured at the end of 20,000 operations. This was rectified by filing the face of the carbons and so ensuring an earlier 'break'. Following this adjustment the switch behaved excellently until a total of 42,000 operations, when a slightly intermittent spark occured at the supply contacts, this condition persisted until the end of the test i.e. 50,000 operations of the switch. On dismantling, the contacts were found to be in a very good condition, and we can say that the switch gave a better performance than that obtained on a standard switch. We consider that if any changes are to be made, carbons of greater sectional area should be incorporated as it was found that by depressing the push button very slowly, and so making the initial engagement on the carbons without the help of the supply contacts, a failure to engage would occur. We think this is due to the resulting sluggish movement of the armature loosing the required momentum to overcome both resistance. [Handwritten: P/5] We have instructed for this switch to be fitted to 39.LX. RM{William Robotham - Chief Engineer}/RC.{R. Childs} | ||