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 report on various types of spark plugs.
| Identifier | ExFiles\Box 33\3\ Scan101 | |
| Date | 9th February 1921 | |
| -2- H85/LG9.2.21. (Faint vertical text on right margin: R.R. Ltd. H.S.B. No. 165/G 194?) Type of plug. No. tested. Test 1. Test 2. Test 3. Test 4. Test 5. Remarks. Bethelem U.S.A. 12 O.K. O.K. O.K. 4 failed. O.K. 4 porcelain cracked. Splitdorf B.148 6 O.K. O.K. 3 failed Mica insulation Mercury GB. 2-point. 6 O.K. O.K. O.K. O.K. O.K. One porcelain found cracked before using. Mercury GB. 3-point. 6 O.K. O.K. O.K. O.K. O.K. Very good plugs. Detachable. Heath. 4 O.K. failed failed Cooke 4-point. 18 O.K. O.K. 4 failed 1 failed O.K. Cannot be cleaned Forward. 6 O.K. failed. Bosch German 6 O.K. O.K. 2 failed Cannot be cleaned. Lodge 19.G porcelain. 6 O.K. O.K. failed. Missed fire badly. Hertz 2-point. 6 O.K. failed 2 failed Mica insulation. Hertz 6 O.K. failed failed Mica insulation - cannot be cleaned. Equem 6 O.K. O.K. failed. Misfiring badly. Champion U.S.A. 6 O.K. O.K. O.K. O.K. leak. Goshawk Car. " " 6 O.K. O.K. 1 failed O.K. O.K. On test Car. " " 6 O.K. failed Missing slightly. Fan Flame 6 O.K. failed Appollo 6 O.K. failed failed. | ||