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).
Design of oil relief valves and the challenges related to the flexibility of bow springs.
| Identifier | WestWitteringFiles\O\January1926-March1926\ Scan101 | |
| Date | 3rd March 1926 | |
| TO R.{Sir Henry Royce} FROM E.{Mr Elliott - Chief Engineer} Copy to - CJ. " RG.{Mr Rowledge} " HS.{Lord Ernest Hives - Chair} " BY.{R.W. Bailey - Chief Engineer} ORIGINAL E1/M3.3.26. OIL RELIEF VALVES. 5205/8205 We had a scheme nearly completed for the new type of relief valve on Phantom engine, but on hearing that the 20HP. chassis was also included in the complaints of lost oil pressure, we produced schemes No. LeC. 2203. & 2207., of which blue prints are attached, for fitting this type of valve to the 10,000 miles 20HP. test chassis. DESIGN OF VALVE. In designing this type of valve we found some difficulty in making the bow spring sufficiently flexible without making it very long. The material we shew is supposed to be .005 thick, and even arranging for the bow spring stress to be nothing at half stroke, the maximum stress grows to 50,000 with valve closed or fully open - (see LeC. 2207.) Under these conditions also the bow spring exerts about .5 lbs. pressure which has to be added or subtracted from the coil spring according to the position of the valve, and increases the spring rating as shewn in the diagram. We roughly confirmed these figures by an experiment on a thin feeler blade. Magneto bow springs for L.T. contacts are .007 thick in bronze and about 1.6" long. They exert a pressure of 2 lbs. fully deflected and probably work at about 1 lb. We shew two types of bow spring, one made of two pieces rivetted together as per your suggestion - LeC. 2207. - (1) | ||