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).
On the rapid wear of distributor contact points caused by excessive cooling of the ballast resistance at high speeds.
| Identifier | ExFiles\Box 168a\5\ img057 | |
| Date | 1st January 1932 | |
| X7720 To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/wst. c.c. Sg.{Arthur F. Sidgreaves - MD} Kor. Hs{Lord Ernest Hives - Chair}/wst.1/AD2.1.32. BALLAST RESISTANCE We have noticed that on 10,000 mile test cars where the average road speeds are high the tungsten contact points in the distributor wear away very quickly and we have come to the conclusion that the cause is the ballast resistance being cooled excessively by the air stream. This was particularly noticeable on 18-GIV where high speeds have been maintained under winter conditions. Messrs. Lucas and Bosch carefully screen their ballast resistance and upon enquiring we learned that it was for the same reason. They have, however, now decided that there is very little case for a ballast resistance and are gradually dropping it altogether like the Americans. We are accordingly arranging for the ballast resistances to be screened on all chassis until our new coil without a ballast resistance is available. Hs{Lord Ernest Hives - Chair}/wst. | ||