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).
Article from 'The Autocar' discussing the composition and analysis of aluminium pistons.
| Identifier | ExFiles\Box 35\2\ scan 004 | |
| Date | 28th November 1914 | |
| THE AUTOCAR, November 28th, 1914. Aluminium Pistons. Their Exact Composition. The Results of an Analysis. SOME months ago we first drew attention to the fact that certain go-ahead makers in France and Belgium were successfully using aluminium pistons. Very great interest was taken in the news, because it seemed to offer a possible solution of the problem of how to make a light piston without having recourse to very thin material. It is a well-known fact in engineering that, however strong a material may be, there is a limit of thickness below which it is difficult to go. For instance, cast iron is stronger than aluminium, but if it be reduced so that the piston is really light very considerable manufacturing difficulties are encountered, as such extraordinary care has to be taken to ensure that no one part is cut a shade too fine. On the other hand, with aluminium quite a thick piston can be cast which at the same time is very light. This is roughly the attraction of aluminium, and it does not apply to pistons only, but to a number of other parts of the modern automobile. Nevertheless, the work imposed upon a piston is very different from that expected of an aluminium crank chamber or gear box, and it was imagined that there would be many difficulties to overcome with an aluminium piston, particularly in the way of collapse under heat, possibility of the piston rings cutting into the grooves of the relatively soft piston, and of the gudgeon pin working loose in the gudgeon pin lugs. It was, therefore, generally assumed that some very special alloy of aluminium would have to be used if a satisfactory aluminium piston was to be made. These aluminium pistons were only to be obtained in France and Belgium, and the war has rendered it impossible for them to be secured. However, in the meantime good reports of their behaviour have come through from various sources, and at least one manufacturer has standardised them. A few days since we were able to secure a piece of an aluminium piston cast in Belgium, and we have had it analysed with the following result: Per cent. Copper ... 6.80 Zinc ... 2.44 Iron ... 0.14 Silicon ... 0.22 Aluminium (by difference) ... 90.40 ... 100.00 The specific gravity is 2.87 (water=1). Our analyst reports that the above figures represent a very ordinary cast aluminium mixture, except that usually in cast aluminium the above proportions of copper and zinc would be reversed. It, therefore, follows that those who have hesitated to experiment with aluminium pistons because they believed that some very special alloy was necessary need no longer hesitate. We hope, therefore, that those who have been interested in the subject will no longer delay to experiment, as there certainly seem very considerable possibilities in the aluminium piston providing a really light reciprocating piece which will require no very special difficulty in manufacture, and which will, consequently, be cheaper to make than either a light cast iron or steel piston. Handwritten text: 20/SIX | ||