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).
Material composition and properties of aluminium pistons, comparing hard and soft results.
| Identifier | ExFiles\Box 142\2\ scan0049 | |
| Date | 8th July 1923 | |
| 45524 BY.{R.W. Bailey - Chief Engineer} E... g.{Mr Griffiths - Chief Accountant / Mr Gnapp} Sft.{Mr Swift} c. Hs.{Lord Ernest Hives - Chair} O...Hm.{Capt. W. Hallam - Head Repairs} EP{G. Eric Platford - Chief Quality Engineer}9/Hl8.7.23. re. ALUMINIUM PISTON MATERIAL. With reference to the trouble we have had recently in regard to pistons which we have considered rather too soft, and better results have been obtained by the presence of more iron - the following is some information I have received from Oy. at Springfield with reference to their experience and action which they have taken and are now taking in regard to pistons which they are now using on the Springfield made 40/50 cars. "Our pistons have in the past year or eighteen months run all the way from extreme hardness and brittle-ness to extreme softness. At one time they were so brittle that they broke on the machines. This was found to be due to a combination of high magnesium with pouring at too high temperature. Eliminating these two faults and fixing a pouring temper-ature of 1210° F gave us good pistons, and addition of .5 to 1.0% tin gave us cleaner metal, more consistent results and better machining properties. There is still a varia-tion between hard and soft, however, which we have just investigated in two extreme cases. These were hard. soft. Copper 8.20 7.40 Iron .54 .46 Tin .84 .47 Ours specification to the manufacturers calls for Copper 6.5 to 8.0 Tin .5 to 1.0 Iron .8 max. Other elements are considered impurities and their total should not exceed 1%. Of this no individual element should exceed .5%. Brinell 52 - 72 The figure given is taken .125 below surface on 1" diameter bar cast in sand mould. Tensile Ult. Y.P. Elong. in 2" 20,000 16,000 2% Stanton Minimum 250 blows (.312 drop) | ||