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).
Standardisation and design of battery ignition contact breaker points, comparing tungsten and platinum.
| Identifier | ExFiles\Box 163\7\ img100 | |
| Date | 4th March 1927 | |
| X4284 To R.{Sir Henry Royce} from EFC. c. BJ. E.{Mr Elliott - Chief Engineer} c. Wor.{Arthur Wormald - General Works Manager} Da.{Bernard Day - Chassis Design} c. BY.{R.W. Bailey - Chief Engineer} Rg.{Mr Rowledge} EFC3/T4.3.27. BATTERY IGNITION CONTACT BREAKER AND CONTACT BREAKER POINTS X.2894.X.1818. X.4041.X.4275/84. Your reference EL/M23.2.27. Before finally standardising tungsten points we consider it advisable to await the verdict of the impending 20 H.P. 10,000 mile test which will be run with these points. In the meanwhile we are suggesting that a further stock of platinum points be not ordered without first communicating with this Dept. Both the evidence of our own tests and that of Messrs. Johnson Matthey's analyses is that our own tungsten as obtained from Messrs. Reynolds is identical with that of Delco-Remy ignition. They are both pure tungsten with traces of iron only. We therefore foresee no difficulty in obtaining a large supply of known good tungsten points. American Bosch is not interchangeable with Delco. We do not see that it would be any easier or more desirable to make our ignition interchangeable with American Bosch than with Delco-Remy. Yes, we are now O.K. on production with both oil excluding devices a to LeC.2121, and ventilation both in contact breaker base and in distributor head (two gauze windows). Regarding the effect of quicker break generally, so far as our tests show, running at various speeds, this seems to have very little effect if any on platinum points, but there is an indication of an improvement with quicker break on tungsten points. We have never thought that the usual argument for quicker break is applicable to any useful degree. We have asked the D.O. to instruct a cam which will give about 50% quicker break than make. This cam will be useable with the standard lever or with the off-set lever. The actual duration of the make is fixed by the electrical characteristics of the coil and the value of the condenser, and has all along been 50-50. As to whether an advantage may be gained by altering the duration of the make would depend upon what other alterations were made to the coil to suit the changed duration. The minimum value of current at break divided by condenser capacity for a given energy of spark, and secondary voltage with given secondary, would be obtained by having a very small inductance, large capacity, and small period of make, as was done in the Atwater Kent ignition with the trip operated contact which could not remain closed. This also gives a high efficiency because of the small resistance | ||