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).
Magnetic interference of speedometers caused by their proximity to the ammeter.
| Identifier | ExFiles\Box 59\2\ Scan337 | |
| Date | 22th January 1934 | |
| 86051. Cx.{Major Len W. Cox - Advertising Manager} From Hs{Lord Ernest Hives - Chair}/Wst. c. to Wor.{Arthur Wormald - General Works Manager} c. to Sg.{Arthur F. Sidgreaves - MD} c. to By.{R.W. Bailey - Chief Engineer} c. to EV.{Ivan Evernden - coachwork} Hs{Lord Ernest Hives - Chair}/Wst.1/MA.22.1.34. MAGNETIC INTERFERENCE OF SPEEDOMETERS. Replying to your Cx.{Major Len W. Cox - Advertising Manager}1/KW.20.1.34., the same magnetic interference action has always existed on our chassis where the speedometer has been placed close to the ammeter but it has not been appreciable owing to the fact that a moving coil type of ammeter was fitted. This expensive type of instrument by virtue of its inherent design features is magnetically stable andunaffected except by extremely strong external magnetic forces. On the present 20/25 and the new 40/50 instrument patch we have placed the ammeter and the petrol gauge meter as far away as possible from the speedometer, and the fact that a sheet metal instrument mount is used also helps to screen the speedometer magnetic interference. We suggest that we offer Mr.Sears the alternative of a special moving coil ammeter if he still wants his instruments arranged as stated. Hs{Lord Ernest Hives - Chair}/Wst. | ||