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).
From Specialloid Limited detailing piston manufacturing and the properties of Specialloid Y alloy.
| Identifier | ExFiles\Box 148\4\ scan0288 | |
| Date | 22th September 1934 | |
| Specialloid LIMITED Friern Park, North Finchley, N.12. -3- Messrs. Rolls Royce, Ltd., 22nd September, 1934. ance unless the external lands are machined to the correct shape. The direction of the Piston expansion (controlled by the sections) must obviously be taken into consideration when deciding the finish land dimensions and this explains why we have evolved the oval and taper turned Piston and have manufactured special oval and tapering chucks and jigs to perfect our final machining operation. The skirt and upper lands of the Piston are machined oval with the major axis on the thrust sides and the minor axis across the gudgeon pin faces; in addition the skirt is tapered from a smaller diameter at the top to a larger diameter at the bottom, thus the skirt of the Piston forms a frustum of a cone. 5) Material. For compression ignition and internal combustion Pistons we prefer to use either our Specialloid S.12 (a Cu. al. alloy) or Specialloid Y alloy, and as we would propose manufacturing Pistons for Rolls Royce Ltd., from Specialloid Y, we will only deal in the following paragraphs with that particular material. We have used Specialloid Y alloy for many years and can claim, owing to the endeavours of our Metallurgical Research Department, to have overcome those foundry difficulties experienced with this class of alloy. The Specialloid Piston is cast from a composite die incorporating an internal sand core and an external metal die body, therefore mechanically the casting maintains the strength of a chilled casting. The constituency, heat-treatment and properties of the alloy are as follows:- A) ANALYSIS: Cu. 4% Ni. 2%, Mg. 1½% B) PHYSICAL PROPERTIES: Specific Gravity 2.80 Co-efficient of Expansion .000022 per °C C) HEAT TREATMENT: Soaked for 6 hours at 500-520°C, followed by a further soaking for 4 hours in boiling water (100°C), then allowed to cool in the atmosphere. The last four hours period is an artificial age hardening treatment. We should like to record here that we have installed a special plant for the heat-treatment of Y alloy which | ||