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).
Letter detailing the composition and properties of the new AC.9 bearing material.
| Identifier | ExFiles\Box 115\5\ scan0078 | |
| Date | 4th July 1938 | |
| BUY 17a Agents Copy. R R FE/EHF. Attention of Hugh Gardner, Esq. 4th July, 1938. Messrs. L. Gardner & Sons, Ltd., Patricroft, Manchester. Dear Mr. Gardner, Since discussing with you recently the subject of the new RR. AC bearings, a change has been made as regards the material, the latest improvement being known as AC.9 in place of the former AC.6. This change was made principally to ensure sound castings, and incidentally the results of engine tests seem to prove that the AC.9 is, if anything, superior to AC.6. The details of AC.9 are as follows - COMPOSITION. Tin Nickel Copper Magnesium Silicon Iron. 5.5 - 6.6 1.5 - 1.8 0.6 - 0.9 0.7 - 1.0 0.2 - 0.4 0.2-0.4 The maximum Brinell is about 75, the general figure being about 55 to 75 Brinell. The specific gravity is about 2.95 to 3.00. The co-efficient of expansion is 0°C. to 150°C.(.0000225). The heat conductivity about 36 c.g.s. units which is three times that of steel, and five times that of normal Babbit. The anti-corrosion properties are very good, as indicated by exposure to air, etc., nor is it liable to corrosion as a bearing in contact with oil; this is known to occur with Cadmium and Lead Bronze. The Brinell hardness is only slightly reduced when at 150°C., whereas normal Babbit metal falls from 30 Br.{T. E. Bellringer - Repair Manager} in the cold to about 5 Br.{T. E. Bellringer - Repair Manager} at 150°C. Interference Fit. We recommend that bearings are fitted with their outside | ||