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).
Analysis of valve-seat 'pick-up' issues, heat transfer properties of valve materials, and a review of a paint-spraying apparatus.
Identifier | ExFiles\Box 174\2\ img288 | |
Date | 1st December 1938 guessed | |
Fig. 9. Diagram Labels: Outlet temp. Inlet temp. Water outlet Beaker for measuring water Water inlet Valve Sil-o-Cel brick Thermocouple Alloy block of constant temp for heating valve Top of furnace Table of Thermal Conductivity: Material | Sec. per Cc. per Deg. Fahr. | Sec. per Cc. per Deg. Cent. --- | --- | --- No. 1 Silcrome | 147 | 0.049 No. 2 Silcrome | 147 | 0.049 CNS | 174 | 0.058 Cobalt chrome steel | 183 | 0.061 Std. 1925 steel | 390 | 0.134 Copper | 2,820 | 0.940 Sodium (liquid) | 624 | 0.208 Mercury | 57 | 0.019 Aluminium | 1,450-2,900 | 0.50-1.00 TABLE III. MISALIGNMENT BETWEEN SEAT AND STEM OF VALVE DURING 50-HR. TEST, MEASURED IN RUNOUT AT VALVE SEAT. Valve No. | At Start. | At Finish. --- | --- | --- 1 | 0.0020 in. | 0.0001 in. 2 | 0.0010 | 0.0009 3 | 0.0015 | 0.0010 4 | 0.0005 | 0.0007 5 | 0.0013 | 0.0020 Fig. 10. Chart - Y-axis (left): Conductivity of copper insert valve stems B.T.U per h.p. per hr per sq.ft per in. per deg. fahr - Y-axis (right): Increase in conductivity over that of Solid Steel - X-axis: Dia. of copper insert percentage of valve stem dia. - Plotted Lines: Cobalt chromium, Chromium nickel silicon dynamometer test show that these valves maintain the alignment of head and stem remarkably well, as recorded in Table III. This fact is important, as valves which seat properly will run much longer than valves that are unseated, however slightly. A valve-stem composed of copper for 40 per cent. of its diameter will actually transmit three times as much heat as a Preventing pick-up on valve-seats. One other subject at present very important to truck and motor coach engine manufacturers is that of "pick-up," or "warts," on valve-seats. Small file-hard spots appear on the seat of the valve and wear the block-seat down very rapidly. The exact cause of this pick-up is not known, but I believe that it is essentially a heat condition. At high temperatures the material of the valve has an affinity for the material of the block. The very outer layer of block-seat material is probably at a high heat, approximating exhaust temperature. This thin outer layer causes the trouble. block seat or using a seat-insert material other than grey iron is a solution of this problem. Cooling the valve with copper or sodium helps to overcome this trouble. The use of vacuum cups is recommended for grinding valves, particularly for those with large heads. Spanner holes and screw-driver slots weaken the valve-head and are likely to cause distortion. Paint-spraying apparatus. WE have received from Aerostyle, Ltd., 174-176, St.{Capt. P. R. Strong} John Street, Clerkenwell, London, E.C.3, a catalogue illustrating their paint-spraying system. This is an underslung type of gun, the portable outfit having a total weight of 49 lb. The apparatus includes an air-cooled compressor driven by a V-belt from a 1/4 h.p. electric motor. Alternative bowls are provided, holding 1 pint and 1 1/4 pints. The apparatus should have a wide range of utility. | ||