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).
Investigation and test report on Lucas ammeters.
| Identifier | ExFiles\Box 168\5\ img343 | |
| Date | 11th December 1937 | |
| To By.{R.W. Bailey - Chief Engineer} c. to By/RD. 6132 RM{William Robotham - Chief Engineer}/RC.{R. Childs}3/JH.11.12.37. LUCAS AMMETER. Lucas ammeters, three in all were handed to us at various times between the dates 6.11.37. and 22.11.37. for investigation, with a view to be fitted to the car. In considering the adoption of this instrument for standardisation, we had first to decide what is the real use of an ammeter on the car. From experience of car drivers in general, we should say that in the vast majority of cases, the ammeter is not so much used as a measuring instrument, as a mere indicator. From this we conclude that the accuracy of the indications is not so important as the precision and consistency with which they are made. Commencing with this premise, these ammeters were examined on the bench, with respect to a number of points, arranged in an order of importance as follows :- (1) Soundness of insulation. (2) Freedom from sticking of the pointer. (3) Oscillation of the pointer and damping. (4) Reliability : freedom from derangement and consistency of operation. (5) Correctness of zero position, and front appearance generally. (6) Accuracy of indications. (1) In view of the move towards supplying the system with less fuses, the question of insulation becomes most important. With this in mind, the ammeters were subjected to an insulation test at an A.C. pressure of 200 volts. They were found to be quite satisfactory. (2) Of the three instruments, two showed signs of sticking of the pointer. On one instrument in particular the momentum of the pointer, in taking up a position half way across the scale, carried it right across the scale where it stuck. The instrument had to be tapped to bring the pointer back to zero. Generally the instruments gave the impression of being slightly sluggish. | ||