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 failure of umbrella valves on an E. A. C-1 engine after 250 hours of testing.
| Identifier | ExFiles\Box 72\1\ scan0176 | |
| Date | 1st November 1923 | |
| R.R. 493A (40 H) (SL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} EXPERIMENTAL REPORT. Expl. No. 9770 9060 REF:Hs{Lord Ernest Hives - Chair}5/LG26 11.23. FAILURE OF UMBRELLA VALVES (E.70818) ON E.{Mr Elliott - Chief Engineer} A.{Mr Adams} C-1 ENGINE. All the exhaust ^valves of this type on the E.{Mr Elliott - Chief Engineer} A.{Mr Adams} C-1 engine stretched to the extent of .010" to .035" after 250 hrs. normal running during various tests. The lengthening was due to the flattening of the convex head. The bending took place at the narrow section of the head (see sketch). With the exception of one valve, the stretching was not due to non-seating, as examination shewed that the faces had been firmly in contact with the seats and had been operating normally. The most heated part of the valve seems to be the centre of the head down to just past the part where the radius joins the stem. This was confirmed by observation when running with the open exhaust. It would probably result in better cooling if the valve guides were slightly lengthened towards the head, or the present exposed stem masked. The influence of the rim or increased section round the valve head was noticeable in the case of the valve which failed through not seating correctly. The heat seemed to have been conducted from the non-seating part of the rim. contd:- [Sketch 1 caption] DOTTED LINE SHEWING HOW VALVE FLATTENED [Sketch 2 caption] HOT PART SHADED | ||