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).
The development of a production test for ignition coil cases made from Redmanol material.
| Identifier | ExFiles\Box 69\1\ scan0047 | |
| Date | 13th April 1927 | |
| X8710 EFC. PC.132. April 13th, 1927. DEVELOPMENT OF PRODUCTION TEST FOR REDMANOL IGNITION COIL CASES. For the purpose of evolving a specification of test for ignition coil cases produced in Redmanol material, six such cases were obtained from production on which a number of tests were carried out. The tests naturally resolved into an investigation of the behaviour of the coil case material, when raised to a fairly high temperature, and subjected to high electrical pressures. Method of Testing. To test the cases, they were placed in an electrically heated oven in which temperatures ranging from atmospheric to 1000C, could readily be obtained. By means of two close fitting electrodes, one inserted inside the case, and the other round the outside, a high D.C. difference of potential was applied across the wall of the case; The necessary high direct voltage being obtained and measured as described in the general report EFC1/T29.4.27 - Rectifying Unit for High Voltage D.C. Tests of Insulation. A galvanometer reading up to 950 micro-amperes was used for the measurement of leakage current passing through the case. Tests and Results. Throughout the tests the average operating voltage of the trembler coil was 5.5 volts and of the valve filament 5.1 volts. Preliminary tests shewed that as the temperature of the case was raised, the leakage through the material or the conductance was considerably increased, accompanied by lowering of the available applied pressure. In order to compare results, therefore, the ratio of the applied volts (as measured by the spark gap) to the leakage current in micro-amperes, expressed in megohms, was taken as a figure of merit in each test. Generally, the applied pressures ranged from about 10,300 volts at 200C down to 1,000 volts at 900C, and the | ||