The Aprilia MotoGP bike you’ve never seen

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The second version of Aprilia’s original and scary RS Cube MotoGP bike appeared briefly during testing in late 2004, then disappeared forever. Two decades later we fully reveal the bike for the first time

Aprilia RS Cube in matt black livery

The second-generation Cube was completely redesigned for 2005, then hidden away in Aprilia’s top-secret race department for decades

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A few months ago I was talking to Aleix Espargaró about Aprilia’s long and winding road to the summit of MotoGP, from the 500cc two-stroke twin of the 1990s to the historic 2022 RS-GP via the RS Cube, the notoriously wild machine which during the 2003 German GP caught fire and nearly barbequed Colin Edwards.

“You should go to Noale,” said Espargaró, bubbling with excitement, like always. “They have the prototype 2005 RS Cube there, which they never raced. It’s all carbon-fibre – beautiful!”

Not exactly an invitation, but I was going anyway. After September’s San Marino GP I drove to Noale, where I was asked to leave my car, suitcase and laptop bag outside the heavily secured race-department gates, because secrets…

The Aprilia Cube was ahead of its time, crazy loud and super-fast

Any factory race department is a Holy of Holies. The foyer of Aprilia Racing tells the company’s story: first there are the 125, 250 and 500cc two-strokes, which made the marque a global force, winning 38 world championships and 294 GP wins between 1985 and 2011.

Then there’s the first RS Cube, raced between 2002 and 2004, several RSV4 Superbikes and finally the RS-GP family, from the 2015 MotoGP/Superbike hybrid to today’s title challenger. And there, mounted on the wall, all alone in a gleaming cabinet, is the Holy Grail, the constructors’ trophy for Aprilia’s first MotoGP victory, in Argentina last April.

The RS Cube was Aprilia’s first MotoGP bike and the most radical machine on the grid when the 990cc four-strokes lined up for the first time at Suzuka in April 2002: pneumatic valve springs, ride-by-wire throttle and carbon clutch. No other MotoGP bike featured these technologies back then, but they all do now, so Aprilia was ahead of its time. And the Cube was slightly lighter than its four- and five-cylinder rivals, because the rules allowed three-cylinder machines a ten-kilo advantage.

Aprilia RS Cube side profile

The 2005 Cube featured a more compact engine, allowing a longer swingarm for more grip and Honda RC211V-style rear suspension

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The Cube was also crazy loud and super-fast – the loudest bike on the grid and the first four-stroke MotoGP bike to crack 200mph, during practice for the 2002 Italian GP at Mugello. It was a shame that the Cube wasn’t as good at going around corners as it was rocketing down straights, which is why it didn’t score a single podium during its three years in MotoGP.

By the way, Gigi Dall’Igna was heavily involved with the Cube. He eventually became manager of the project and looked after the transition to the 2005 engine. Earlier he had fitted his first downforce wings to the Cube, a decade before he joined Ducati and made downforce aerodynamics the big deal in MotoGP. In 2004 he switched jobs, returning to smaller two-strokes, which is where he had started at Aprilia in the early 1990s, helping design the factory’s first RSV250 engine.

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Some argue that Aprilia’s first and biggest mistake with the Cube was hiring Formula 1 engineering legends Cosworth to design the engine: which was basically three cylinders off a ten-cylinder three-litre F1 engine. F1 engines are designed for peak power, because F1 cars have loads of grip, while MotoGP engines should be designed for part-throttle power, because they have much less grip.

The Cube had a super-light F1-style crankshaft, so it picked up revs so fast that neither the rider nor the rear tyre could keep up.

“It wanted to kill you everywhere,” says Jeremy McWilliams who raced the Cube in 2004. “It made lots of horsepower but in all the wrong places. I think it broke every one of my ribs twice that year,

“The engine had a very light crankshaft, so it had too little inertia, so as soon as you opened the throttle the rear tyre would spin. We were always asking for more inertia, but they said there was no room in the engine.

“It also had this really weird torque curve, so the engineers tried to fill in the holes in the curve with clever fuel and torque maps. It started making torque at around 9000rpm, then it dropped away and then there was a really sharp torque peak at 12,500, which sent the bike sideways and fired you on your nose.”

Regis Laconi on Aprilia RS Cube

A wide-eyed Regis Laconi and the original RS Cube during the 2002 Italian GP at Mugello, where the machine became the first MotoGP bike to break the 200mph barrier

Aprilia

Aprilia therefore almost completely redesigned the Cube for the 2005 season. Engineers retained the inline triple layout, but changed the cylinder angle, increased crankshaft inertia and generally made it more of a MotoGP engine than an F1 engine. The original Cube engine was so F1 that the engine and gearbox were essentially separate units, something which motorcycling had given up many decades earlier.

“We kept the pneumatic valves, and the cylinder head and the injection system were similar, but we changed the layout,” says Germano Bergamo, Aprilia’s racing vehicle design manager, who has been with the company since before it won its first world title in 1992.

“We made the new engine a single unit, integrating more parts. For example, typically in F1 the scavenge pump is mounted outside the engine and Cosworth used this system when they designed our engine. We moved the pump inside and also fitted the auxiliary systems like the water pump, fuel pump and generator on the same axis behind the cylinders.

“We also moved the countershaft from below the crankshaft to above the engine. All these changes made the engine shorter and more compact. For example, without the scavenge pump mounted outside the front of the engine we could put the exhausts closer to the engine, leaving more room for the radiator and oil cooler.”

The more compact engine was housed in a completely new chassis, CNC-machined from solid billets of aluminium alloy. This was a new and much improved way of fabrication, because the various sections don’t need to be heated and bent into shape, which had been the traditional method for decades, causing all kinds of inconsistencies, so no two chassis are ever quite the same.

Aprilia RS Cube engine

The first RS Cube engine, designed by Cosworth. Note how the engine and gearbox units are separate, like a Formula 1 engine. This made the engine too long, which compromised chassis design

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The shorter engine also allowed a longer swingarm. “You get a bigger lever with a longer swingarm,” adds Bergamo. “So this is better for traction and chain force.”

Aprilia wasn’t above copying Honda when it came to the detail design of the swingarm. After all, Honda’s RC211V was the best motorcycle in MotoGP at the time.

“We studied the linkage used by Honda,” Bergamo continues. “They fitted the shock directly to the swingarm, so we used this idea to reduce the chatter that the rear wheel can transmit to chassis.”

“We had ride-by-wire throttle but it was opened and closed by cable, to give riders the sensation they were used to”

McWilliams and veteran Aprilia test rider Marcellino Lucchi (who beat Valentino Rossi to win the 1998 Italian 250cc GP) had their first runs aboard the new Cube in late 2004, but the bike went largely unnoticed because everyone was much more interested in the latest RC211V, Ducati Desmosedici and Yamaha YZR-M1.

Bergamo was confident that the new Cube would get Aprilia closer to the front of MotoGP than the original, which had never bettered the sixth place Edwards achieved at the 2003 season-opening Japanese GP.

“I think results would’ve been better in 2005,” he says. “The overall conception of the machine was improved and we had around 240 horsepower [at 18,000rpm], about ten more than the previous bike.

“The biggest problem was managing the engine with the electronics. This was absolutely the beginning of the electronics that MotoGP has now. We had some ideas about traction control and other electronic controls, but we didn’t have the experience to manage so much horsepower. We wrote our own software for TC, anti-wheelie, engine-braking, launch control and anti-jerk. It was the beginning, so it was basic stuff, nothing like what we have now.

Aprilia RS Cube chassis and engine

The more compact second-generation Cube engine, plus chassis machined from solid aluminium billet

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“Although we had ride-by-wire throttle, the actual throttle was opened and closed by cable, to give riders the sensation they were more used to. All the electronic controls were based on different gas maps, not by adjusting the injection or timing. Plus, of course, we didn’t have any gyros or accelerometers, so it was only the beginning of this work.”

And then the end…

Piaggio – already owners of Vespa, Derbi and Gilera – had bought Aprilia (and Moto Guzzi) in August 2004. In January 2005 the company decided to axe the Cube project.

From the archive

“The decision was to stop the Cube project and move all the staff at Aprilia Racing into studying and developing a new Aprilia superbike, the RSV4. We worked in partnership with the road-development department, employing a lot of concepts we had used on the Cube, like the ride-by-wire system, using an upper and lower injector in each throttle body and so on.”

The RSV4 was launched in 2009 and won the World Superbike title in 2010, 2012 and 2014.

The RSV4 engine was also used to power Aprilia’s next MotoGP bike, the ART, which was created in 2012 to compete in the championship’s low-cost CRT category, created in the wake of the global financial crisis.

The Superbike engine was housed in a prototype chassis, made from both machined and extruded sections, to reduce costs. Espargaró had some great rides on the ART, often hassling full MotoGP prototypes and winning the 2012 and 2013 ART titles. This machine then became the basis for the first iteration of the RS-GP family, raced in 2015, still using the RSV4 engine. The 2016 RS-GP was Aprilia’s first fully prototype MotoGP bike since the Cube.

Thus you can trace the lineage of the current RS-GP all the way back to the RS Cube, because every lesson learned with each motorcycle is incorporated in the next machine.