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).
High voltage test report comparing the merits of Maconite, Glover's, and Helsby ignition cables.
| Identifier | ExFiles\Box 168\1\ img044 | |
| Date | 7th June 1926 | |
| EFC. WB.{Mr Brazier/Mr Bell}93. 7.6.26. HIGH VOLTAGE TESTS OF IGNITION CABLE. X.86. X.B60. The object of this test was to ascertain the respective merits of Maconite H.T. cable and our present standard (Glover's) cable when subjected to a high alternating potential (See E1/M26.5.26.). Two samples of each cable were tested. The first samples of cable were subjected to 15,500 peak volts which resulted in the Glover cable cracking badly and puncturing after 8 mins, whereas the Maconite went for 45 mins. before subsequently cracking and puncturing. The second samples were subjected to 16,500 peak volts which cracked and punctured the Glover cable after 30 mins. duration, whereas the Maconite sample only exhibited slight cracking and did not break down. A similar sample of Helsby cable (sometimes used on production) was also tested and gave distinctly good results, puncturing after 35 mins. at 15,500 peak volts without exhibiting any previous cracking of the rubber. To further test Maconite cable samples of Maconite and Glover cable were twined round the H.T. electrodes of our ignition spark gaps, the central conductor of the cable being connected to the earthed side. The Maconite sample broke down after 3 hrs. under these conditions whereas the Glover sample broke down after 1.5 hrs. In each case examination revealed that cracking of the insulation had occurred previous to the breakdown. From these tests Maconite is apparently superior to the Glover cable when subjected to conditions as outlined above. EFC/HEW. | ||