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).
Endurance test report on a 20/25 HP starter switch to investigate contact burning.
| Identifier | ExFiles\Box 168a\2\ img040 | |
| Date | 4th April 1931 | |
| X6121 By.{R.W. Bailey - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/H.E.W. c. E.{Mr Elliott - Chief Engineer} c. Wor.{Arthur Wormald - General Works Manager} Sg.{Arthur F. Sidgreaves - MD} Hs{Lord Ernest Hives - Chair}/HEW4/ADM.4.4.31. 20/25 STARTER SWITCH. We have carried out an endurance test on the bunch of a standard 20/25 HP. starter motor switch completely dry, in order to observe the amount of burning of the contacts in view of the fact that the majority of switches sent in for repair have the oil level below the switch contacts. The switch was connected up to a standard 20/25 HP. starter motor operating at normal voltage with the load adjusted for a running current of 120 amperes. Operation of the switch was effected automatically and in all 20,000 starts were made at the average rate of 10 starts a minute. After 6,000 starts had been made the switch was dismantled for examination. The copper contacts shewed signs of burning which was not considered excessive so the switch was reassembled this time (at the request of Hy{Tom Haldenby - Plant Engineer}) without the paxolin tube which fits inside the case. 14,000 further starts were then made without interruption or failure and the switch again dismantled. No appreciable wear of the switch plunger had occurred but the outer switch contacts had burnt away at the point of contact on the average about 30% of the thickness. In view of the severity of the test, however, we do not consider that this is excessive and upon shewing these contacts to the production people they stated that switches came back for repair in much worse condition. No effect was observed as a result of the deletion of the paxolin tube. We are of the opinion that rapid wear of switch contacts in service is not so much due to loss of oil as the incomplete operation when starting up i.e. customers do not push right down each time and in consequence the switch contacts suffer. Some definite relay operation would appear to be indicated. Hs{Lord Ernest Hives - Chair}/H.E.W. | ||