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).
Excessive wear on distributor contact points, concluding that varying ballast resistance temperature is the cause.
| Identifier | ExFiles\Box 61b\2\ scan0170 | |
| Date | 2nd June 1932 | |
| X6118 To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Wst. c. Sg.{Arthur F. Sidgreaves - MD} c. Wor.{Arthur Wormald - General Works Manager} c. E.{Mr Elliott - Chief Engineer} Ev.{Ivan Evernden - coachwork} Hs{Lord Ernest Hives - Chair}/Wst.2/AD2.6.32. R.R. DISTRIBUTOR CONTACT POINTS Although we have improved the surface condition of the distributor tungsten contacts, we still get excessive wear on the points. On exptl. cars the points are practically finished after 15,000 miles. After a number of tests and observation of points on cars we have definitely come to the conclusion that this excessive wear is due to the ballast resistance temperature varying. With a ballast in the ignition circuit, every time the engine is started an excessive current is broken at the points until the ballast warms up. Also according to external atmospheric temperature conditions and the speed of the car a cooling draught impinges on the ballast resistance causing considerable variations in its working temperature and consequently the working current of the ignition circuit. We reported some time ago the effects of these cooling draughts after observation of the points on high speed 10000 test runs in France, particularly on 18-GIV. As a final test we ran an unballasted American outside primary coil for 500 hours on the bench with an R.R. distributor and the points at the conclusion of the run had only worn .002", the condition of the surfaces being equally as good as standard. On 19-EX which has only run 7000 miles, the points are going rapidly. This is therefore another strong argument for dropping the ballast resistance on our cars. We are arranging to send you the contact points in question for your inspection. Hs{Lord Ernest Hives - Chair}/Wst. | ||