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).
Analysis of petrol pump current and voltage conditions using oscillograms, comparing different coil housings and a patented modification.
| Identifier | ExFiles\Box 149\3\ scan0033 | |
| Date | 24th February 1939 | |
| 1263 To By.{R.W. Bailey - Chief Engineer} c. to By/RD. c. to Rm{William Robotham - Chief Engineer}/RG.{Mr Rowledge} Rm{William Robotham - Chief Engineer}/JBD.{John B. Dixon - Fuel Systems}6/JH.24.2.39. PETROL PUMPS. With the cooperation of Mr. Shaw we have obtained the attached oscillograms of the current and voltage conditions at the contact points. B. The present standardised H.P. pump on Wraith and Phantom III. This pump is fitted with steel coil housing. The bottom left hand graph shows the voltage between the two contact points. This remains at the battery potential until the points make and then falls to zero, and on the points separating rises to 100 volts which is sufficient to cause arcing and burning of the points, although there is a resistance of 100 ohms in parallel with the coil to prevent this. The right hand bottom graph shows how the current in the coil builds up during the stroke but at the speed at which the pump was working only reached a value of 1.2 amps, with a rapid fall at the end of the stroke although the closed circuit current reaches 3 amps. It is the rapid cut off with the inductance of the coil which causes the high voltage shown in the previous graph. A.{Mr Adams} These are similar graphs for the H.P. pump fitted with the cast iron coil housing. The two right hand graphs give the current and voltage in the pump as it is supplied and are similar to the graphs described above. The voltage curve here, also rises at the point of break to about 100 volts and causes arcing. The top left hand graph shows the current when our additional resistance and contact are fitted for which we have applied for a patent. | ||