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2009 R1 might not be the prettiest looking bike, but
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<blockquote data-quote="MotorToad" data-source="post: 488928" data-attributes="member: 14083"><p>The "tire recovery time" theory is starting to die off. I don't want to try to disprove it since I think there's something to it, but I've heard it's not what's actually occurring.</p><p></p><p>The main benefit to the cross-plane crankshaft is the conservation of kinetic energy. On a flat-plane crank all four bouncy bits stop completely twice a revolution, which means the crank and flywheel mass have to jerk them all back the other direction at the same time. The amount of energy needed to do that increases with revs and can be close to the engine's total torque output at the revs GP bikes are running, which makes for horrible spikes and valleys in the resulting power output. With the cross-plane crank, half the bouncy bits are at 100% velocity when the other half are stopped. Even though the pistons have to be jerked back the other direction, it's only half as many and the other half are helping the crank's mass to do it. The downside to the cross-plane is that it requires balance shafts to control the wobble, the crank's no longer symmetric and the ends want to travel in circles out of phase with each other. You can see the lobes for the counterbalancers on the front of the engine. Traditionally, this extra spinning mass has made the crank too heavy for racing use, but as revs go up needs change.</p><p></p><p><img src="https://www.superbikeplanet.com/image/archive/08ymr1/engine.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Yamaha's BSB team messed with changing the cam timing to make the engine a "big-bang" (180-<strong>180</strong>-180-360, where two cylinders fire on the bold), so far as I know they ran it for part of a season and dropped it. I think Kawasaki's GP engine uses that or maybe even a "double-twin" crank and, well, the results speak for themselves. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p></blockquote><p></p>
[QUOTE="MotorToad, post: 488928, member: 14083"] The "tire recovery time" theory is starting to die off. I don't want to try to disprove it since I think there's something to it, but I've heard it's not what's actually occurring. The main benefit to the cross-plane crankshaft is the conservation of kinetic energy. On a flat-plane crank all four bouncy bits stop completely twice a revolution, which means the crank and flywheel mass have to jerk them all back the other direction at the same time. The amount of energy needed to do that increases with revs and can be close to the engine's total torque output at the revs GP bikes are running, which makes for horrible spikes and valleys in the resulting power output. With the cross-plane crank, half the bouncy bits are at 100% velocity when the other half are stopped. Even though the pistons have to be jerked back the other direction, it's only half as many and the other half are helping the crank's mass to do it. The downside to the cross-plane is that it requires balance shafts to control the wobble, the crank's no longer symmetric and the ends want to travel in circles out of phase with each other. You can see the lobes for the counterbalancers on the front of the engine. Traditionally, this extra spinning mass has made the crank too heavy for racing use, but as revs go up needs change. [IMG]https://www.superbikeplanet.com/image/archive/08ymr1/engine.jpg[/IMG] Yamaha's BSB team messed with changing the cam timing to make the engine a "big-bang" (180-[B]180[/B]-180-360, where two cylinders fire on the bold), so far as I know they ran it for part of a season and dropped it. I think Kawasaki's GP engine uses that or maybe even a "double-twin" crank and, well, the results speak for themselves. :) [/QUOTE]
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2009 R1 might not be the prettiest looking bike, but
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