Long refinement of a single concept

Brand-new concepts are not necessarily better than an older, but refined, idea

When I think of England’s central role in the development of sports and racing motorcycles, I see long development of quite basic designs. The three obvious ones are the great racing singles from Norton, AJS and Velocette. In the case of the AJS, the overhead cam drive they first tested – by roller chain – was retained to the end of the big singles era in 1962. But in the early 1920s they oscillated between OHC and OHV, and tried various oiling schemes. In 1956 the 500cc variant known as the Matchless G50 came into being, also with the prominent magnesium casing for its chain cam drive.

Norton was presented – as all makers were – with the rich menu of engineering choice bequeathed them by the Kaiser War’s aircraft engine development. They adopted pushrods-and-rockers OHV but weren’t sure about an oiling system. In 1924 they hired Walter Moore (he had the reputation of a problem solver) to make an Isle of Man TT winner of their Model 18. Looking for brakes, Moore found something workable in Model T Ford rear 8-inch drums. Former fighter pilot Alec Bennett duly won the TT. The following year they adopted dry sump oiling with a double plunger pump and won everything. For 1927 Moore kept the crankcase, flywheels, con-rod and piston to build the SOHC Norton CS-1. With a few hiccups it was continual refinement through testing. Former TT rider Joe Craig eventually became Norton’s racing development engineer, using extensive dyno simulation runs as a means of developing virtually unbeatable reliability, not only over the 37-mile laps of the TT but also in European GPs.

Velocette’s Goodman family decided to switch from their previous two-strokes to what appeared to them to be the coming thing in four-strokes – overhead cam. Their 350 single with shaft-driven SOHC would become the admired KTT production racer, its design advancing in performance and reliability yearly.

This process of refinement was able to remain ahead of continental makers by the force of Laurence Pomeroy’s observation that “the first instance of novel principle is invariably defeated by the developed example of established practice”.

Because the development never ceased, the established practice of the British single-cylinder race engine was a moving target. Ernest Henry’s concept of four valves per cylinder, operated by two overhead camshafts, revolutionised auto racing from 1912 onward, but as an air-cooled 500cc motorcycle twin after the First World War it accomplished little. It was fast but subject to overheating.

British singles ruled until 1939, the year of what some called ‘the Nazi TT’, when on the eve of the Second World War a supercharged BMW won the Senior. And Norton ruled again after the war, taking a last 500cc world title in 1951 and a last Senior TT 10 years later. That Norton single brought forth vigorous offspring. When bearings magnate Tony Vandervell decided to build his own GP car instead of entering bought-in Ferraris, the well-proven characteristics of the ‘Manx’ Norton 500 cylinder head became the basis of the 2.5-litre ‘Vanwall’ four project, begun in 1954. It won its first races in 1957 and took the F1 title the following year. Norton’s tradition of steady detailed refinement of gas flow and combustion was one of the original bases of Britain’s present-day ‘Formula One District’, centered on Banbury.

There has been a tendency for degreed engineers to want to redesign things the moment new understanding arrives, but there is also value in having long experience with an existing design, and continuing to upgrade it incrementally. Britain’s Air Ministry bought a few US Curtiss V-12 engines after they were successful in 1920s Schneider Trophy air racing. While continuing to develop other engines, Rolls-Royce began to develop their own V-12s, one of which – the ‘R’ air racing engine – eventually brought the Schneider Trophy to Britain permanently.

The resulting ‘Merlin’ military piston engine, of which more than 150,000 would be produced, was a continuous evolution consisting mainly of finding ways to supercharge more fuel-air mixture into it while simultaneously maintaining service reliability.

Its power was more than doubled between 1939-1945, and in the postwar world its suitability for US air racing gave it a second ‘developmental life’ in which for short periods its output was boosted to over 4000hp. Meanwhile, German aviation, more driven by advanced research and dreams of war-winning ‘superweapons,’ dissipated much of its budget on novel concepts such as jet and rocket engines – projects too immature to make any substantial contribution to that nation’s war effort.

There can be value in developing radical and promising new solutions, but there is also value in realising the potential remaining in well understood and therefore highly reliable existing designs. Design maturity takes time, and that can give great value to time already invested. US aviation was the ultimate beneficiary of advanced German wartime R&D.