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).
Recommendation and test results for using AC.9 die-cast material for engine bearings.
| Identifier | ExFiles\Box 115\3\ scan0226 | |
| Date | 9th May 1938 | |
| -2- Our recommendation is that ½ a dozen Bentley II cars should be put through production with AC.9 die cast in place of the normal AC.7 billet cast for the confirmatory evidence. This memo. releases AC.9 die-cast material for the Wraith III big end and standardisation sheets will be issued for the Bentley II big ends, Phantom III big ends in the same material and following success on Bentley II mains on ½ a dozen cars a sheet issued for this also. The actual conditions under which the endurance was carried out were particularly severe and consisted of the following over the 40 hrs. run. Each 1 hr. 30 mins. at 4,000 2½ mins. at 4250 and 5 mins. at 4500. Each 10 hrs. 7 hrs. full load, 2 hrs. ½ load and 1 hour ¼ load. Thin oil was used namely Mobiloil Arctic at an inlet temperature to bearings of 100 - 110°C and pressure of 30 lbs.sq.in. The point of running AC.9 material was in regard to its ease of casting and reduction in percentage scrap compared with all previous AC alloys as confirmed by the foundry. By die casting the material cost which is the high figure in the production of bearings in AC. alloys will be reduced by approximately 66% and also has the advantage of requiring only one heat treatment as compared with two on the billet. We would point out that all the clearances and interference fits were as used on std. production B.II. The big end bearings were of thin section .06" thick without shims and similar to results obtained on Phantom III, Bentley II and Wraith III in various alloys these are averagely a big improvement over the previous thick section bearings. This improvement we consider is due to the fact that the rod housing is much stiffer and provides a more solid backing for the bearing. | ||