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).
Aircraft auxiliary power systems, including power take-off, generators, gearboxes, and electrical system specifications.
| Identifier | ExFiles\Box 27\3\ Scan227 | |
| Date | 15th May 1939 guessed | |
| 21. the reason for such a high power take-off, and apparently it has been arrived at by incorporating a large factor of ignorance. Thoughts of cabin supercharging are also prevalent. It is from this drive that the power for the 5 KW generator is being taken. The project is still secret, but apparently the constant speed drive will be at 2 x engine speed and will incorporate a carbon disc clutch which will slip to maintain constant speed. Eclipse are not so insistent on the merits of high voltage as they were, because an investigation made by the Navy into the variation of weight with voltage has shown the minimum to be with 24 volts. It has also been found less important to maintain such close control of frequency for radio work as had been thought necessary, and it is probable that the bulk of the electrical services will be operated on a 24 volt system, with a 1KW generator operating at 110 volts 800 cycles for radio. Falling off in frequency below 800 cycles is not nearly so important as overspeeding. In common with the engine firms, Eclipse had done little to develop gearboxes, except insofar as encouraged by the military authorities. The military specifications issued so far however, appear to be unduly ambitious, and result in 8-unit gearboxes weighing about 80 lbs. and capable of driving 60.HP. Gearboxes are not popular with the engine people on account of the difficulty of housing them in single-engines machines. On the question of auxiliary power units opinion was again divided. The large auxiliary engine built for the Douglas D.C.4 has given trouble, and will probably not be perpetuated. As already mentioned, there is great interest in main engine drives, and exploratory work is also being carried out on small engines. For instance, the Navy has ordered a 2-cylinder air-cooled engine as an alternative for the 5 KW generator. Should it be decided finally to instal auxiliary engines as the main source of power for ancillaries, the need for supercharging has been realised, and tentatively it is proposed to use the main engine exhaust for this purpose. | ||