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 and leakage figures for various sheet insulation materials.
| Identifier | ExFiles\Box 39\3\ Scan268 | |
| Date | 16th September 1926 | |
| Contd. -6- EFC1/T16.9.26. Results for sheet materials:- The sheet materials were placed on a metal plate covered with tin-foil to ensure good contact, which foil formed one electrode. The other electrode consisted of foil on which stood a metal block carrying the connecting terminal. Four 1/16" discs were first tested, two of American linen based material (yellow) and two of British canvas based (brown), using about 14 sq. ins. of upper electrode. The results are shewn on accompanying curves from which it is seen that the American material is considerably superior. A few repeat readings made afterwards confirmed this result. Tests were then made as below on some samples using a 9 sq.in. electrode and a test voltage now of 1200 R.M.S. The samples were Messes & Mitchell's grades "L" (linen base) and "O" (canvas base) .067" thick of yellow colour; and Micanite & Insulator Co.'s Nos.1 and 2 (canvas base) .035" thick, brown. Leakage figures are micro-amperes. Sample. | L | O | 1 | 2 | |---|---|---|---| | 3170 | 1250 | 6000 | 4500 | | 785 | 140 | (approx) | (Approx) | | | 70 | | | Contd. | ||