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).
Testing a modified piston valve for the Autovac petrol feed system to improve slow running.
| Identifier | ExFiles\Box 40\4\ Scan182 | |
| Date | 20th September 1926 | |
| AUTOVAC PETROL FEED. We have received on test the first "Piston Valve Suction elbows" made by R.R. Ltd. These function equally as well as those supplied to us by the Autovac Co in response to our request for something to reduce the bad effect on slow running, during the period in which the petrol in the Autovac is open to the induction pipe depression. We have made a piston valve in which the piston spindle, instead of being slightly tapered at the end, is parallel throughout its length. The object of this is to increase the restriction still further. When experimenting previously with permanent restrictions, in the form of small holes, we found it necessary to use one hole of .046" diam: to gain any appreciable improvement; accordingly it was thought that an ordinary working clearance (.002") between the spindle and its guide would not be an excessive restriction. This was found to be the case; by using a parallel spindle the suction period is increased very slightly as compared with a taper ended spindle as designed. The improvement is only very slight and can not be detected except by timing the suction period, the improvement measured by this means is 8%. It is expected that it will give a greater improvement after considerable use; we can expect slight wear to take place between the spindle and | ||