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).
Modifications, improvements, and wear issues concerning the S.U. petrol pump.
| Identifier | ExFiles\Box 163\1\ img039 | |
| Date | 21th February 1938 | |
| 6007 TO By.{R.W. Bailey - Chief Engineer} c. to By/RD. c. to Rm{William Robotham - Chief Engineer}/RC.{R. Childs} Rm{William Robotham - Chief Engineer}/JBD.{John B. Dixon - Fuel Systems}1/JH.21.2.38. R.R. S.U. PETROL PUMP. We consider we have effected a considerable improvement in diaphragm material by fitting the oil silk and a mechanical improvement by centralising the pole piece in the magnet pot. These alterations have not given the degree of reliability and increased life that is required. The contact mechanism has not been altered in any way and we give below the reasons why we consider this should be modified. The R.R. SU. contact breaker is fitted with an additional support blade behind the contact blade and the bakelite bridge piece cut away to clear the outer arm of the toggle gear. The position of the outer toggle arm is governed by the strength of the contact spring and thickness of the points. Wear on the contact point allows the outer arm to travel to a position further away from the pot and the armature has to complete a longer stroke before the points separate. This wear in the points diminishes the clearance allowed in the original setting between the armature and the pole piece. Thus an old pump tends to become noisy and ultimately to stick when the setting is used up and the armature is brought to rest before the points break. This modification was originally introduced to quieten the standard S.U. toggle mechanism, but the noise caused by the contacts is not comparable with the impact noise made by the armature hitting the pole piece which always occurs when there is vapour, or air in the system or even in cases of a weak contact spring or very flexible diaphragm. The S.U. contact breaker differs from our own, not having a support blade behind the contact spring, and has a solid bridge piece to limit the travel of the outer toggle arm. The pump is set with the contact blade held back. | ||