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).
Test results for cracking effect and voltage breakdown on four types of cable insulation.
| Identifier | ExFiles\Box 52\1\ Scan130 | |
| Date | 1st December 1929 | |
| -4- EFC {E. Fowler Clarke - Electrical Engineer} 4/AD6.12.29 contd. (6) The cracking effect on the insulation brought about by high voltage oscillatory brush discharges passing along the surface of the insulation to earthed clips thereon. The test carried out over a length of time according to judgement as to the rapidity with which the cracking effect is produced. Gloverite - failed after 2 hours. Super Glover - failed after 8 hours. Helsby - failed after 7½ hours. Maconite - failed after 2½ hours. (7) A sample length of cable bent into a loop about 1½" internal diameter and the loop made to rest upon or touch a hot body at 100°C. at earth potential. A voltage of 10,000 R.M.S. then to be impressed between the conductor and the hot metal body for 30 minutes. If this does not produce failure the voltage should then to be raised and the time extended accordingly. Gloverite - broke down after 27 mins. at 19,200 volts R.M.S. Super Glover - broke down after 14 mins. at 19,200 volts R.M.S. Helsby - broke down after 20 mins. at 19,000 volts R.M.S. Maconite - broke down after 29 mins. at 19,200 volts R.M.S. SECTION (C). Tests on chassis and subsequent electrical tests. Relating to this section of the tests the report WD. {Mr Wood / Mr Whitehead} 92. from my assistant reads as follows :- | ||