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).
Results of gas leakage, gland tightness, and external flash over tests on a set of six plugs.
| Identifier | ExFiles\Box 58\2\ Scan149 | |
| Date | 1st September 1934 guessed | |
| Report No.R.A.E./E.{Mr Elliott - Chief Engineer} and 1.056. -4- The results are given in Table 3 below. The applied air pressure was 600 lb. per sq. inch and the amount of leakage is given in cu. cms. per minute. Table 3 - Gas leakage results. | Temperature. | Plug No.1. | Plug No.2. | Plug No.3. | Plug No.4. | Plug No.5. | Plug No.6. | |----------------|------------|------------|------------|------------|------------|------------| | Atmospheric. | 11.62 | 10.5 | 10.5 | 14.4 | 3.32 | 1.66 | | 200⁰C. | 5.2 | 27.2 | 7.5 | 10.0 | 4.75 | 2.0 | | Atmospheric. | 17.65 | 17.65 | 9.3 | 18.75 | 4.72 | 1.87 | The gas leakage of three of the six plugs is within the maximum of 15 cu. cms./min. permitted by the specification. The major portion of the leakage was through the upper mica washers. 8. Test for tightness of gland. This test was completed satisfactorily. The gas leakage of each of the three sparking plugs was below the permissible amount of 20 cu.cm./min. after detaching and screwing down the gland 20 times. Result satisfactory. 9. External flash over test. Reduced density. For the purpose of this test three of the plugs were in turn screwed into an airtight vessel within which the air pressure was maintained at such an amount as to suppress sparking at the plug electrodes. The external insulation of the plug was under a reduced density of 6 lb. per square inch absolute. Each of the plugs failed to withstand 9000 volts without flashing over the upper surface. The flash over voltages were 8560, 7600 and 8700 volts. | ||