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).
Technical report discussing modifications and performance tests of ignition coils.
| Identifier | ExFiles\Box 163\7\ img245 | |
| Date | 13th February 1934 | |
| -2- Hs{Lord Ernest Hives - Chair}/Wat.2/MA.13.2.34. Cont'd.{John DeLooze - Company Secretary} It is necessary therefore to carry out certain modifications to the coil in the direction of reducing its effective inductance and also by making more use of the temperature coefficient effects on the ballast resistance. For the 20/25, 40/50 and Bentley an ordinary unballasted coil like the Delco Remy and Lucas would probably be quite satisfactory but for extra high speed ignition as required by the SpectreCodename for Phantom III the ballasted coil has a definite superiority. The Delco Remy Co., recently produced what they call an Ultra high speed coil. This has been fully described in the technical press and consists of an ordinary 6 volt coil working on a 12 volt system with a small vibrator which cuts out a protective resistance as the speed increases. At low and moderate speeds the coil has the resistance inserted to protect the coil windings and the contact points from excessive current loading. As the time of make decreases with rise of speed the small vibrator, whose operating coil is connected in series with the ignition coil primary winding, begins to short circuit the resistance and thus at high speeds the 6 volt coil is working direct from the 12 volt system. We obtained one of these coils and made a number of tests to ascertain its H.T. voltage and energy output at various speeds. The results of our tests shewed this coil to give a much higher open circuit secondary H.T. voltage at ordinary speeds but at high speeds there was very little improvement over our standard arrangement. The operation of the vibrator was found to be very irregular and not at all reliable for a given speed. It was considered that by suitably proportioning the electrical constants of our R.R. coil and ballast a performance equalling the Delco-Remy could be obtained without the necessity of extra relay windings and vibrating contacts which must tend to decrease the reliability of the ignition system as well introducing extra complications. | ||