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Old 01-28-2013, 03:43 AM   #9
sendler OP
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Joined: Apr 2012
Location: Syracuse, NY USA
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Here is an interesting quote by DieselMaxPower at the Honda site which explains the conundrum of the power at the rear wheel not being multiplied by using a lower gear even though the vehicle does accelerate much faster. An example would be The CBR250R with an engine power peak at 8,700. If you are rolling along at a steady speed in first at 8,700 rpm, and then crack full throttle, the bike will accelerate violently. We can feel this very obviously. Now do the same in top gear. The bike is felt to start going faster but the rate of acceleration is much, much less. Even though we used the same amount of power from the engine and at the wheel. The acceleration is much greater with the lower gearing but we have put the same amount of power to the ground over time as in the higher gear. There must be some quantity that is increasing at the same rate in either gear (disregarding the higher resistance of speed to wind drag in top gear).
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Ready?
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The ENERGY of the system is increasing at the same rate in either gear. But we are very bad at perceiving energy so it seems like top gear does very little and first gear is doing much more with the same amount of power.
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Example of how bad we are at perceiving differences in energy:
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Cruising along at a steady speed in a car so you can't feel the wind, 10 mph feels pretty much the same as 70 mph. But 70 mph has much more energy and would be a very bad time to run into a wall.
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From DiesleMaxPower
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http://www.cbr250.net/forum/102283-post75.html
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"Torque doesn't do one thing while horsepower does another. Torque is a measure of what's happening to the bike. So is horsepower. It depends on what you want to look at. Torque can give you a way to look at the accelerations. This is great for most humans because we can perceive things like position, speed, and acceleration. Horsepower lets you look at energy. Humans don't have a good way to perceive energy, except for maybe temperature changes which we don't include. When we analyze the dynamics of the bike we look at the speed of the bike (thats the momentum side) and the kinetic energy (thats the energy side). In the simple analysis we're doing now the two are so simplistic that they will always be consistent with one another. It doesn't matter if you decide that torque moves the bike or horsepower. The reason I like to look at HP because the math is much easier, as we've shown with our torque charts. You don't need to transform it through gears."
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