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 expansion characteristics and performance of different engine valve types.
| Identifier | WestWitteringFiles\K\September1923\ Scan2 | |
| Date | 12th July 1923 | |
| R.R. 493A (40 H) (SL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} EXPERIMENTAL REPORT. Expl. No. 4226 REF: Hel/L.G1.9.23. Umbrella shaped Valve 45° - expands .010". After running, this valve shows a very cool head, but a very hot stem. There is not sufficient metal in the top of the stem to carry the heat to the valve seat. Flat topped valve - 45° seats - expands .008". This valve has the same shaped stem as the standard tulip shaped valve. After running it shows a cool head (as cool as the umbrella valve) and a cooler stem than the umbrella shaped valve. The same measuring device was used to find the relationship between the cylinder block expansion and the push rod expansion. Under hottest possible running conditions. The cylinder block expands .013" more than the push rod. There is one period where the cylinder block expands .011" more than the push rod. This takes place when the engine is started from dead cold. The cylinder block becoming heated more quickly than the push rods. Now if we use a 45° tulip valve and give no clearance in the tappets when cold, we get .002" clearance when the engine is heated up. Comparing this with the 15° tulip valve, which , under the same conditions as above gives .002" clearance when hot (i.e. the valve is .002" off its seat) we find that the 45° valve -should expel any possibility of valve burning, or distortion caused by valves not seating properly owing to their expansion taking up all the tappet clearance. contd:- | ||