The Approachable Nortons

Norton’s release of a new “all-British V4” has us sifting through the sands of time, starting with the Monocoque Commando.

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by Phil Aynsley
The Monocoque Commando, designed by innovative Norton engineer Peter Williams.

Norton’s tie-up with respected U.K. automotive engineering firm Ricardo has resulted in an all-new V4 engine. It’s the first clean-sheet 4-stroke performance model the famous company has made since the 1970s. Computer-designed and painstakingly developed, it is Norton’s new platform off which several models will spin.

This isn’t the first time a motorcycle manufacturer has joined forces with the car industry. Harley-Davidson did it twice with Porsche. The first time, in the 1980s, was the still-born “Nova” V4 engine. Their second union conceived the Revolution engine range, which powered the liquid-cooled V-Rod family launched in 2002.

However, Norton only needs to look back into its own history to read a cautionary tale. In the early 1970s it worked with Cosworth on what it hoped would be a world-beater, the so-called Norton Challenge P86. Sadly, this was a dead-end and the project was soon abandoned.

Long forgotten, it unexpectedly reappeared in the mid-1980s to win a major international race at Daytona’s speed bowl. The original Challenge project was planned to become the basis of a range of models and the current Norton V4 engine has already achieved this aim. As well as the V4 SS, Norton has revealed three 650cc parallel-twin models based on the V4 engine: the Superlight road racer, and the Nomad and Ranger retro street scramblers. All these bring back memories of Norton golden years of the 1970s. Hang on for a wild ride back in time.

Monocoque Commando

The sales success of Norton’s 1968 Commando was underpinned by its racing efforts. Just a year after production started, the Commando was up on the podium at major events in the U.S. and U.K. Often forgotten in the hype of Triumph’s legendary 1969 Isle of Man TT Production win at 99.99mph is that Norton rider Paul Smart finished second at 99.37mph.

Cross-pollination of U.S. and U.K. racers helped develop the free-form Formula 750 racing class. This inspired Norton racer/design engineer Peter Williams to modify a Commando frame for the first event in 1971. He quickly followed this with what he called a “mini-Commando” with aerodynamics and pannier fuel tanks the main features. Superstar racer Phil Read took one to fourth at Daytona’s 200 meeting, showing a potential that Williams fully exploited with the monocoque of 1973. It was the most successful racing Commando Williams built. Advanced aerodynamics helped gain speed from an aging engine design, while fuel and oil were carried low in the frame to ensure high-speed stability.

Standing not much taller than its creator’s knees, it easily hit 160mph on Daytona’s speed bowl. Monocoque chassis were first seen in early 1960s open-wheeler race cars.

Spanish motorcycle factory OSSA developed a monocoque-framed racer that famously finished third in the 1969 250cc World GP championship. So Williams wasn’t the first to build one, but his differed from the OSSA’s magnesium monocoque by using thin-gauge stainless-steel sheets.

Magnesium wheels and fork components helped keep dry weight to just 330 pounds. The engine gained reliability with an outrigger bearing supporting the gearbox mainshaft and the primary drive sped up to reduce torque loadings.

The bike’s overall low profile was helped by having the fuel and oil contained in the large frame enclosing the engine. To save weight, crucial with an engine producing less than 80 horsepower, and to simplify the electrics, fuel was pumped up to the carburetors via the action of the swingarm. An oil cooler was fitted in the front fairing.

Although blighted by carburetion issues at Daytona in 1973, Williams bounced back to win the Anglo-American Easter series on points. He then won the gruelling Formula 750 race at the Isle of Man TT with a new lap record of 107.2mph. Teammate Mick Grant finished second.

Other wins and podiums followed, including second to Giacomo Agostini and his MV, the world’s most sophisticated GP 4-stroke, at Mallory Park’s Race of the Year. Williams is now making replicas of his famous monocoque and is still disappointed his groundbreaking design was shelved.

Spaceframe Commando

Just why a winning formula would be changed so radically after just one season is shrouded in the mists of time. The monocoque frame could be easily lifted off the engine but the actual construction of the chassis was very time consuming. Also, being built to Williams’ exact physical dimensions and preferences, it didn’t suit every rider.

At first glance the space-frame Commando looked very similar to the monocoque but with a small conventional fuel tank above the engine and a secondary tank high in the tailpiece.

The oil tank was mounted low in front of the engine, meaning an oil cooler wasn’t needed. Features like this, and the lighter, short, straight frame tubing, helped lower dry weight compared to the monocoque. Two engines were used: the new, short-stroke 750 and the torquey 828cc now powering Commando’s 850 range.

Using the “850” 77mm bore on a one-piece crankshaft with 80mm stroke (both 850/750 standard stroke was 89mm) with more modern valve angles promised peak performance at over 8,000rpm. The reality was the crankcases couldn’t take the pressure for long, so rev limits were dropped back to around that of the existing 750cc race engine.

Race results were disappointing that year, with one bright spot coming early in the season when Williams and Dave Croxford finished one-two at the Brands Hatch Hutchinson 100.

With the promise of the new, water-cooled Cosworth Challenge ahead, the team pressed on, even testing a spaceframe with monoshock rear suspension.

In August 1974, one of Norton’s darkest days occurred when Williams crashed after the one-piece tank/seat unit dislodged. His injuries ended his racing career and coincided with withdrawal of the team’s main sponsor, cigarette brand John Player.

The air-cooled twin was finally obsolete but there was one chapter left to play out.

Cosworth Challenge

As early as 1973, Norton was building a successor to the Commando. Without the financial resources to develop its own engine lateral thinking had drawn it to Cosworth.

Why not hack two cylinders off the V8 engine that had been dominating the F1 Grand Prix scene since 1966? Ford had funded Cosworth co-founder Keith Duckworth’s innovative engine. This double-overhead cam design featured fuel injection and an industry-leading flat-top piston layout with shallow combustion chambers and four valves per cylinder.

Peter Williams had no involvement with the Challenge (but much later ended up working for Cosworth on its F1 car engines). It was driven by Dennis Poore, chairman of the Norton Villiers Triumph group, who envisaged it both as a race and road engine. Being a former car racer, Poore found it easy to strike up a relationship with Duckworth.

Based on the best features of the F1 3-liter V8, the resulting 750cc parallel-twin had a modern bore and stroke ratio of 85.7mm and 64.8mm with potential peak power of around 120 horsepower at 10,500rpm. But it was heavy and compromises forced between design and production gave it a unique Achilles’ heel.

This was a harmonic frequency so strong it would self-destruct if held at 4,000rpm for more than a few seconds. In a racing situation this wasn’t an issue as the engine ran between 7,000rpm and 10,500rpm. However, 4,000rpm was a typical road cruising speed that could be lethal for both owner and manufacturer if put into production.

More built-in design flaws came with the automotive-based format, not the least of which was a peaky, car-like power delivery totally inappropriate for a motorcycle. Also, the crankshaft didn’t have adequate main bearing support.

It’s easy to make a car engine’s flywheel an integral component located between the crankshaft and clutch (with ring-gear attached for a starter motor). Much less so on a parallel-twin engine, especially when Norton specified it had to have an old-fashioned 360-degree crankshaft throw. So the flywheel sat between the connecting rods, where a crucial third main bearing should have been.

The list of flaws extended to the downdraft inlet ports. Their wide internal diameters were perfect for the high-pressure delivery of fuel injection, but Norton demanded carburetors. Also, a long rubber-toothed belt replaced the car engine’s train of gears. The result was a tendency for the belt to jump, sending the engine’s cam timing haywire.

Cosworth claimed the water-cooled twin made 95 horsepower at 9,750rpm using 40mm Amal Mk II carburetors, and just over 100 horsepower at 10,500rpm running experimental fuel injection.

The engine weighed 194 pounds, of which about 66 pounds was just internal reciprocating mass such as the flywheel and balance shafts. By contrast, a Commando engine, minus carbs, primary drive and gearbox, weighs around 77 pounds.

But several significant features were at least a decade ahead of even Grand Prix motorcycle technology. Major chassis components were hung off the engine supported by small subframes. The swingarm pivoted through mounts cast into the gearbox housing. The rear brake disc was off-board of the swingarm, so wheel and sprocket could be quickly changed. A lot of this clever thinking eventually found its way into the mainstream and can been seen today in MotoGP and Superbike technology.

Much media speculation surrounded lone Norton racer Dave Croxford as he brought the Challenge out for the first time at Brands Hatch in October 1975. The short-circuit veteran only made it to the first corner when a 10-bike pileup ended Norton’s dream. Croxford wasn’t seen again on the Challenge until the first round of the popular Transatlantic Trophy spectacular in 1976. Totally outclassed, it was withdrawn. It made brief appearances at various meetings, including the Imola 200, but never figured in race results. However, the Challenge always put on a show. It looked purposeful, sounded quick-revving and had an exhaust note much like current MotoGP machinery.

Fitting finale

This disastrous story does have a happy ending — in the U.S. In 1984, Cosworth’s new director, racing enthusiast Bob Graves, spotted forgotten Challenge engines in the factory. “You’re looking at the only engine we have ever built which has never won a race,” Keith Duckworth is claimed to have told him. Cashed-up Graves started building a better version with fuel injection and capacity increased to 820cc. Named the Quantal, it involved John Surtees and a network of GP-level technicians. In 1986 GP racer Paul Lewis took the Quantal to second behind Marco Lucchinelli’s air-cooled factory F1 Ducati at Daytona’s Battle of the Twins.

Graves returned with Roger Marshall in 1988 for a truly astounding victory the year after Lucchinelli had won again, this time on a prototype 851. Marshall beat Stephano Caracchi and Ducati’s production water-cooled, DOHC, 8-valve Superbike.

Finally, a British-designed-and-built, water-cooled, DOHC, 8-valver was a world-beater. MC

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