Barrel business conundrums

I was extremely interested and intrigued by the Star letter

'The wrong barrel' in the May edition of TCM. In the late

1950s, I worked at the research labs of The British Aluminium Company, who were collaborating with the Hillman car company in an attempt to produce a hyper-eutectic silicon alloy, for a new all aluminium engine, to be used in a rearengined car, which was to become the Hillman Imp.

I recall trying to produce tensile testing specimens from various formulations of the alloy, but it was extremely difficult to machine. It was almost impossible to produce the smooth surface necessary for tensile testing specimens with the HSS tools then available and these required frequent sharpening.

The problems with machining and excessive tool wear had to wait another 10years or so until Chevrolet were able to develop an all-aluminium block, which utilised electrochemical etching and metal plating of the bores.

Hillman must have thought that an all-aluminium block would both reduce production costs and make it possible to have smaller clearances between piston and block, because of reduced differential expansion. Heat dissipation would also be improved. An alloy block would also be lighter, which would be an advantage with a rear engined car.

Hillman went on to manufacture firstly a block with a dry liner, then a wet linered version, which permitted enlargement from 850cc to 998cc. The wet linered block would of course require precise machining for the liners to seat correctly on their seals. The dry linered engine, similar in principle to that used by many motorcycle manufacturers, should not be confused with the Al-fin barrel, which was perfected by the Ranger division of the Fairchild Engine and Aircraft Co. in 1944 and used in high performance air-cooled engines. The British licensee of this process were Welworthy Ltd. of Lymington.

The Al-fin barrel involved some clever metallurgy with the outside of the barrel receiving a special coating, which permitted the aluminium and cast iron to bond together, rather than be just a very tight fit, as it is in most 'alloy' engines.

There seem to be some unanswered questions about these cylinder barrels. What form did the flaw in the second barrel take? And was the billet used for the 'machined from solid' barrel made from the same alloy? What alloy was the piston?

Casting a third barrel should not have proved to be excessively expensive, as the cost is in the pattern making. When we are eventually able to move freely, I hope I will be permitted to visit the Cross museum at Bath to investigate these questions.