The Myth of Rotating Weight
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ABCDEFGHIJKLMNOPQRSTUVWXYZ
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Rim Weight (kg)12
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Rim moment of intertia (I = MR^2)0.4515840.903168
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conversion from kph to Hz0.13164324470.1316432447
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Speeds (kph)
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101.316432447
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405.265729788
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506.582162235
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607.898594682
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709.215027129
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Energy required to spin (J) (1/2 I w^2)0.78259253751.565185075
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12.521480625.0429612
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19.5648134439.12962687
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28.1733313556.3466627
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38.3470343476.69406867
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Power required to accelerate from 0 to given speed in 1.5 seconds (W)
0.52172835831.043456717
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8.34765373316.69530747
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13.0432089626.08641792
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18.782220937.5644418
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25.5646895651.12937912
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Let's say in a crit you slow down to 35 kph and re-accelerate to 40 kph, in 1.5 seconds, how much power does that take?
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(Ignoring all air resistance, the dominating source of power draw)
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Light RimHeavy Rim
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Initial velocity (kph)3535
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Final velocity (kph)4040
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Time (s)1.51.5
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Initial kinetic energy (J)56.84756105113.6951221
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Final kinetic energy74.24987566148.4997513
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Difference17.4023146134.80462922
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Power11.6015430723.20308614
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Power required for 80kg rider + bike
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3780.864198
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4938.271605
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1157.407407
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771.6049383
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So it takes 10 W more to accelerate the heavy wheel, but it *already* takes 771W to accelerate the rider + bike, ignoring air resistance.
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So that's a 1-2% difference, even before you consider aerodynamics.
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For an average rider with a CdA of 0.3, at sea level, with normal Crr and normal drivetrain losses, 200W gets you about 35 kph, 300W gets you 40 kph
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