The specifications for Ducati's GP11 MotoGP bike as furnished by their PR arm note that the engine in the fire red machine is a liquid-cooled, 90 degree V4 four-stroke, desmodromic DOHC, four valves per cylinder" unit. The transmission? Six-speed cassette-type gearbox, with alternative gear ratios available. Dry multiplate slipper clutch. Chain final drive.
Carburetion? Indirect Magneti Marelli electronic injection, four throttle bodies with injectors above butterfly valves. Throttles operated by EVO TCF (Throttle Control & Feedback) system.
Suspension: Ohlins upside-down 48mm front forks and Ohlins rear shock absorber, adjustable for preload, compression and rebound damping.
How is the machine stopped? Brembo, two 320mm carbon front discs with four-piston callipers (sic). Single stainless steel rear disc with two-piston callipers.
Chasiss? Ducati's official technical specifications page offered to the media does not even mention the frame or chassis. On one of Ducati's consumer sites, it does mention that the frame material is carbon fiber. No other details are provided.
Insiders in Italy profess that they are mystified as to why the GP11 Ducati MotoGP bike is struggling to the degree that it is today, because, they say, the 2011 version of the Ducati MotoGP bike isn't that much different from the 2010 version that Casey Stoner won races on.
So what's going on? Some of the best information coming out of the Ducati MotoGP team this season has not been via press release. It actually comes from an unlikely source: Ducati mechanic Alex Briggs' Twitter account (@Alex__Briggs). Briggs is a longtime MotoGP paddock wrench and came to Ducati from Yamaha with Jeremy Burgess; they started working together for HRC with rider Michael Doohan. Briggs has worked with Rossi for over a decade. He published some of the first photographs of Rossi in Ducati leathers, and is quite forthcoming when interacting with fans regarding developments at the Ducati MotoGP team.
Briggs offered an clear baseline of what the Ducati chassis is, and is not, in a Twitter post dated September 15.
Briggs wrote: 101 the Ducati Chassis. All the GP bikes other than the Ducati have a aluminum frame (or u can call it a chassis) that u can take the engine out & still wheel it around the workshop. In fact u could ride it down a hill, corner & brake no problem. But our bike is different. The engine IS part of the frame! So if u remove the engine u end up with a swingarm & seat on the ground + a front wheel, forks & airbox on the ground. Can't push the sucker anywhere. Now basically both the front & rear parts r made from carbon fiber. They bolt 2 the engine 2 make the bike complete. Are u still with me?
At the risk of repeating the obvious, the Ducati GP 11, like the GP10 that Stoner rode and won races on last season, does not have a conventional frame. It does not have familiar-looking frame rails that connect the steering head and the swing arm pivot in one very conventional and cohesive package. The Ducati MotoGP bike essentially uses a long carbon airbox assembly to join the front end of the motorcycle and the engine.
"Stressed member". The Ducati MotoGP bike, like the Britten and other bikes dating back to the 1930s, uses the engine as a stressed member of the chassis. As Briggs states--The engine IS part of the frame!. This is not a new concept inside Ducati Corse—Ducati have won races using a three-piece MotoGP bike, it's just in the last ten months that the bike has regressed from being a race winner to a bike that a nine-time world champion is slotting in at the back of the grid. Conventional chassis stiffness in motorcycle racing is a subject with a multitude of opinions as to what works and will not work, but the majority of those opinions are formed using motorcycles with a very similar chassis, made of aluminum, which cradles the engine and also connects the steering head to the swing arm pivot. Now throw most of that out and use the engine cases as the middle of the frame. Countless new variables enter the mix. Motorcycle chassis need to flex. Do engine cases flex? Can one engineer flex into a three-piece engine design?
In a general sense, this "three-piece" approach to a chassis leans more to Formula One than motorcycle racing, (although all Ducati MotoGP bikes, even the 2003 trellis-framed units, have used this design philosophy in one way or another). As far back as the 1960s, F1 has tried to compartmentalize the front suspension, engine and rear suspension.
While it was reported and rumored that Ducati would come to Aragon last weekend with an aluminum, Yamaha-style Deltabox chassis around the GP11 engine, the reality is that the photos of Rossi's GP11 at Aragon showed the addition of what can be termed an alloy brace and not any kind of new, conventional frame made from aluminum.
There is no doubt that Ducati has a true aluminum chassis in development, British Moto2 firm FTR made the "brace" for the GP11 and is presumably modding up a full alloy frame for the de-stroked GP12 engines to slip into seamlessly.
Ducati has begun to build towards debuting their next generation flagship streetbike, one which debut at the Milan show later in the season. Rumors have it as a derivative of the MotoGP bike with the engine as a stressed member. While the link between that motorcycle and the documents filed by Ducati with the USPTO are at the moment unclear, Ducati does indeed seem to have invested a great deal in the "three pod" design.
