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 composition and performance of alternative bearing and valve seat insert materials.
| Identifier | ExFiles\Box 115\5\ scan0048 | |
| Date | 27th May 1938 guessed | |
| As mentioned to you there was an alternative material known as AC.9. and just as a matter of interest we are giving you the analysis of this material, which in all other characteristics may be regarded as responding very much in the same way as AC.9, but it was feared at one time that there may be trouble due to segregation and for that reason the Antimony has been eliminated from the AC.9 specification. AC.9. Composition. Nickel Manganese Tin Antimony Magnesium Silicon Iron. 1.7% 0.7% 5.0% 0.50% 0.0% .50% .3% Specific Gravity - 2.85 to 3.20 Co-efficient of expansion - 0°C. to 150°C. .0000225. Incidentally, we ourselves have had no trouble in the production of AC.6. bearings either as castings or the machining of them, but as there is this fear that it may arise on the AC.6. material, we propose to proceed only with AC.9. Further, as mentioned to you, the trial at AEC. over 100 hours run is more than encouraging, as diamond turning marks in the bearing were visible throughout practically the whole of the area of the bearings, and the main journals were hardened to about 500 Brinell whereas the crank-pins were left soft, that is the normal softness of the material, which is about 250 Brinell. As to whether the material will be 100% perfect on soft shafts remains to be seen, as at the moment Rolls seem to be definitely against putting it on to soft shafts until they have concluded experiments now proceeding, to prove the material satisfactory under such conditions. However, we were pleased to hear from you that in making a trial of these bearings you would bear this point in mind and not judge the material too harshly if it did not show that very improved running performance which we should expect from it, particularly if it were on unhardened shafts. Regarding the question of Valve Seat Inserts, in the I.A.E. report there was a material, that is a Molybdenum-Chrome Iron, which came about fourth or so on the list, very close to Stellite, the approximately composition of which is as follows - Total Carbon ...... 2.9 - 3.3 Silicon ............2.2 - 2.6 Sulphur ............Max. .10 | ||