Valve Angles: A Postscript

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I should have been cured of any obsession with combustion chamber shapes and valve angles at the age of 14, when, having spent a considerable sum of pocket money on a copy of The Automobile Engineer I nearly went mad endeavouring to follow the arguments of Ricardo, Whatmough and Weslake as to whether turbulence, squiz, swirl or stratification was the best way of flowing the charge into a cylinder head. It was like trying to understand Relativity or the Universe. Afterwards I kept my two bob (10p) for the annual Motor Show Extras of this learned publication, with their fine photographs of engines, transmissions, springing systems, and brakes, etc.

However, following last month’s piece about valve angles, I think I should tell you of another valve formation I came across the other day. It was described in a patent taken out in May 1921 jointly by a gentleman with the marvellous name of Signor Lanzerotti-Spina and Mr KJ Thomson. Spina had designed a complicated aero engine during the war and had some association with the Thomas Inventions Company, formed with Thomas Foreign Patents Ltd, to promote the inventions of JG Parry Thomas, who before he became Brooklands’ most successful racing driver of the 1920s, had himself designed a 350hp eight-cylinder X-formation water-cooled aero engine while Chief Engineer at Leyland’s in 1917 and prior to that had invented the Thomas electro-mechanical transmission and was later to patent the torsion bar springing, in conjunction with anti-roll bars of that type, used on his Leyland Eight car.

KJ Thomson was the brother of Hedley Thomson who had financed the Thomas Inventions ventures and who after Parry Thomas’s death at Pendine in 1927 formed the partnership of T & T (Brooklands) Ltd with Kenneth Taylor, Thomas’s skilled engineer and machinist.

Anyway, what the patent covered was a cylinder head with valves at a steep included angle, but with their stems pointing inwards instead of outwards, the combustion chamber they occupied being concave instead of convex. It was intended for large engines with four or more valves per cylinder. The advantages claimed were ports that would emerge vertically from the flat top of the head, the close proximity of the valve stems simplified (the patent drawing showed pushrod and rocker actuation) valve operation, and if a valve stem broke the valve would be restrained by the cylinder walls from falling into the cylinder, which was a more common cause of mechanical mayhem then than now.

Finally, a PS to this PS: in last month’s piece some italics crept into the last paragraph which made a nonsense of the respective valve-angles of the 1919 3-litre Bentley and the racing 1914 Humber and Mercedes which W O had studied at the design stage. These were 30-deg; 90-deg; and 60-deg respectively, which was the point of the argument. WB