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).
The testing and modification of dashboard instruments, including ammeters, petrol meters, and gauges.
| Identifier | ExFiles\Box 62\2\ scan0086 | |
| Date | 13th August 1932 | |
| -2- Ammeter. Smiths recommended us to buy the Lucas moving iron ammeter. As our tests showed the Lucas ammeter to be sound electrically, this was agreed to especially as Smiths have a commercial agreement with Lucas which is to our advantage. These ammeters with the exception of a slight amount of needle oscillation due to the fact that they are not electrically damped, have not given any trouble and read correctly. We have asked Messrs. Lucas to try and damp these instruments in some way. In carrying out dynamo voltage regulator tests we have found that certain type of regulators which have a low periodicity seriously affects these moving iron ammeters so that it becomes impossible to read them. We are still therefore keeping the moving coil ammeter in view. Electric Petrol Meter. This meter owing to the fact that it has a weak magnetic field is affected considerably by any extraneous magnetic effects. It was found necessary therefore to move it as far away as possible from the magnetic speedometer. There is still a slight oscillation of the meter needle occasioned by the rise and fall of the potent-iometer float arm in the petrol tank due to swirling of the petrol. Calibration tests carried out by Hs{Lord Ernest Hives - Chair}/Les with a petrol tank showed these meters to read reasonably correctly. Oil Pressure and Water temp. gauge. These are now working satisfactorily. Road tests showed the necessity for recoiling the thermometer tube with its coil axis normal to the instrument in order to prevent transmitted vibration to the needle. The instrument dials have also had to be screwed in position to prevent these working loose. | ||