While the company's flagship sportbike was heavily updated in '07, Yamaha has further revamped the R1 for '09. The highlight is the use of a "crossplane" crankshaft that spaces the journals at 90-degree intervals as opposed to the traditional 180, giving the engine an uneven firing order. The design is based on experience from the M1 MotoGP program and is said to provide a "more linear driving force in response to throttle movements and more linear controllability when exiting a corner for maximum acceleration."
In a typical engine, vibration is caused by the piston moving up and down, accelerating and decelerating with every stroke. Counterweights on the crankshaft are used to offset some of the weight of the piston, ring and connecting rod assembly, but this simply transforms some of the up/down inertia to a fore/aft direction as the crankshaft spins. Multi-cylinder engines allow each cylinder's inertia to be offset with another's; for example, in an in-line twin-cylinder engine, the rising piston nicely offsets the falling piston, eliminating primary vibrations-those acting at crankshaft speed. Because the cylinders are separated, however, a rocking couple is created. A four-cylinder engine with a conventional crankshaft eliminates that rocking couple because each set of rocking pistons is offset by the second set. There are still secondary vibrations and moments-those acting at twice crankshaft speed-present in a conventionally laid out four-cylinder engine, and these are sometimes dealt with by a small shaft rotating at twice crank speed
In a typical engine, vibration is caused by the piston moving up and down, accelerating and decelerating with every stroke. Counterweights on the crankshaft are used to offset some of the weight of the piston, ring and connecting rod assembly, but this simply transforms some of the up/down inertia to a fore/aft direction as the crankshaft spins. Multi-cylinder engines allow each cylinder's inertia to be offset with another's; for example, in an in-line twin-cylinder engine, the rising piston nicely offsets the falling piston, eliminating primary vibrations-those acting at crankshaft speed. Because the cylinders are separated, however, a rocking couple is created. A four-cylinder engine with a conventional crankshaft eliminates that rocking couple because each set of rocking pistons is offset by the second set. There are still secondary vibrations and moments-those acting at twice crankshaft speed-present in a conventionally laid out four-cylinder engine, and these are sometimes dealt with by a small shaft rotating at twice crank speed
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