A Ricardo Engine

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Having, on another page, reviewed Sir Harry Ricardo’s very enjoyable autobiography, recently published, it was interesting to come upon an article of his in The Automobile Engineer of 1923, about the 3-litre racing engine which he designed for Vauxhall, so that they could compete in the 1922 T.T.

This Vauxhall engine was of twin-overhead-camshaft type and looks very complex but is described as remarkable in its orthodoxy. Straight-sided cams were used, and except in the case of the exhaust valves, low carbon mild steel was employed throughout, even for the built-up crankshaft, instead of resorting to high duty alloy steels. The bearings were ball and roller type for the mains and roller for the big-ends, running on case-hardened pins, to ease the lubrication problem. The webs were shrunk onto the crankshaft as in marine and large gas engine practice. The timing and distribution gears were supported on both sides, to ensure close mesh adjustment. The detachable heads were regarded as unique for a racing engine at this date, at all events in Europe. There was provision for three sparking plugs per cylinder, of which only the central one was used. Carburation was by two separate instruments arranged one to feed the two outer cylinders, the other the inner cylinders of this 85 x 132 mm. four-cylinder sixteen-valve engine.

It is interesting that Ricardo was aiming to run it continuously at between 4,000 and 4,500 r.p.m., with short bursts of 5,000 r.p.m., and that he deliberately ran the cylinders at a considerable temperature, using steel (L. A. Pomeroy, in “The Grand Prix Car”, said cast-iron) liners in an alloy block (Bolster, in “Specials”, says the block was cast-iron). Originally he had planned for a c.r. of 7.5 to 1 but he actually used a 5.8-to-1 c.r., the engine running satisfactorily on high-grade petrol or lesser petrol with the addition of 25% to 30% of benzole—it is necessary in this context to remember the low-octane values prevailing in 1921/22.

These engines were beautifully made at Vauxhall Motors and the one tested by Ricardo at Shoreham never had its heads removed, the valves examined, or the tappets adjusted; when it was returned to the makers they stripped it and found the mechanical condition excellent, although the tests occupied many weeks. The engine gave 129 b.h.p. at 4,500 r.p.m., and a maximum b.m.e.p. of 159 lb./sq. in. at 3,700 r.p.m., with a mechanical efficiency of 78%. The brake thermal efficiency of 32.1% was believed by Ricardo to be the highest ever achieved to that date, running on petrol. He estimated that in the car a fuel consumption of nearly 40 m.p.g. would have been possible running at 48½ m.p.h. on an economical carburetter setting. He also observed that while the valve gear and spur-gear timing train “could not be described as silent”, the valve gear being decidedly noisy at below 2,000 r.p.m. compared to that of a side-valve touring car engine, little could be heard of the timing gears, and that as engine speed increased the volume of noise from the valve gear appeared to diminish but the timing gears became distinctly audible, making a high pitched whine instead of a singing noise at over 4,000 r.p.m. But the greatest noise was air-intake roar, although this did not increase above 2,500 r.p.m. The engine was at first lubricated with castor oil, later with special Shell racing oil.

C. E. King of Vauxhall Motors designed the very advanced and ingenious chassis, for the three engines built. They were completed just before the T.T. was due to be run and due to inadequate testing, says Ricardo, “a defect made itself manifest on the actual day of the race after lying dormant throughout the practice runs. It put two of the cars out of the race and compelled the third to run with the utmost caution”. This defect was remedied and one of the cars “set aside for competition work”. Mr. King’s chassis “unlike the engines, never showed any weakness at all”, Harry Ricardo generously admitted.

In fact, Park’s car retired on the second lap, Swain’s on the fifth lap, in the T.T., due to the Ricardo slipper pistons breaking up (although Pomeroy said a big-end roller-bearing broke up on one car), in this astonishing engine with its bronze heads and central flywheel. Payne’s Vauxhall finished third, behind the winning Sunbeam and the Bentley, at 52.71 m.p.h., compared to the race average of 55.78 m.p.h. These Vauxhalls were run at Brooklands for many years, still in non-streamline form, when they could lap at over 108 m.p.h., while a streamline two-seater body was put on one by jack Barclay, Cobb lapping in this Vauxhall at over 116 m.p.h. Amherst Villiers supercharged one of these T.T. engines, which apparently gave between 200 and 250 b.h.p., and was eventually made to give 300 b.h.p. .or more as Raymond Mays’ Villiers Supercharge sprint car.

A fine tribute to Sir Harry Ricardo, whose book you should read.—W. B.