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 performance of ignition coils and contact breakers, detailing current consumption and mechanical operation.
| Identifier | ExFiles\Box 34\1\ Scan043 | |
| Date | 4th February 1919 | |
| R.R. 235A (500 T) (S.D. 408. 26-4-17.) Bm. 2/156/13. X.2812. -3- EFC5/T4.2.19. Contd. 2. Comparative volt-ampere characteristic curves of a 12 volt 48 watt M.I. lamp and of nickel wire ballast resistance giving the same resistance at one particular point. (14") 3. Curves giving the current consumption of the A1 and B type coils for different speeds of the contact breaker and with the make ratios indicated, and ballast resistance adjusted as already described. (20") (31" and 18" respectively) The point on the A1 curves at which signs of missing begin to occur on the bench, is indicated by 'm' and the increase in missing denoted by various letters until the last letter, which indicate "Sparks all out". It will be seen that on the 'B' curve we have no indication of any missing up to the speed to which we carried the test. Together with these curves, are curves showing the mechanical operation of the contact breaker making use of the reading of average current sent by the battery, through a non-inductive resistance in series with the contact breaker. It will be seen how well this current keeps up as the speed rises for both the .7 and the .4 make ratios, which proves that we are not up against any mechanical deficiency of the contact breaker. Regarding this ignition for the production car, the D.O. have now in hand the instructioning of this work and will get out a cam, as you suggest, to give a simple harmonic motion with a .5 make ratio. We will reduce the current taken by the coil to the minimum possible amount by the addition of extra ballast resistance to such an extent only that we are quite safe from missing at highest speeds desired. The D.O. have in hand at the same time, the instructioning of a coil very similar to the 'B' type we have been using, but the new coil will be very slightly larger in its dimentions, one reason being that we wish to use one gauge larger wire on the primary winding so as to get as little possible resistance in the coil, and as much as possible outside the coil. The D.O. also have in hand the housing of the condenser inside the contact breaker cover. On the car, with the condenser now fitted, the primary sparking under all condi- Contd | ||