tag:blogger.com,1999:blog-1564958057737541664.post1456591459067395290..comments2016-09-23T13:54:13.397-07:00Comments on On Bicycles, and.... what else is there?: Soda Springs power: error estimatedjconnelhttp://www.blogger.com/profile/01484858820878605035noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-1564958057737541664.post-79631566864910459152009-10-28T10:32:46.987-07:002009-10-28T10:32:46.987-07:00Not quite....
The issue is the wind resistance po...Not quite....<br /><br />The issue is the wind resistance power isn't proportional to speed. You can apply that equation to the climbing power, and to the rolling resistance power times the ratio of rolling resistances (with clinchers and butyl tubes at less than my 140 psi you were probably 20% higher rolling resistance in addition to the mass ratio). But for the wind resistance you should multiply by the cube of the speed and by an additional factor proportional to the cross-sectional area (which is roughly the mass to the 3/4 power, to decent approximation).<br /><br />So your power would be, where<br /><br />Pc0 = my climbing power<br />Pr0 = my rolling power<br />Pw0 = my wind power<br />Mb0 = my body mass<br />Me0 = my equipment + bike mass<br />Crr0 = my rolling resistance <br />coefficient<br />v0 = my speed<br />P = your power<br />Mb = your body mass<br />Me = your equipment mass<br />v = your speed<br /><br />Then:<br />P =<br /> (v / v0) ( Pc0 + Prr × Crr / Crr0 ) × ( Mb + Me ) / (Mb0 + Me0) +<br /> (v / v0)³ Pw (Mb / Mb0)^(3/4)<br /><br />I assume transmission coefficient is the same.<br /><br />Next I'll do an analysis of the effect of speed fluctuations on power. I assume here the bike is moving at a constant speed. However, since wind resistance is a strongly increasing function of speed, above average and below average speed sections, or fluctuations in wind speed, don't cancel.djconnelhttp://www.blogger.com/profile/01484858820878605035noreply@blogger.comtag:blogger.com,1999:blog-1564958057737541664.post-58541434920582034642009-10-28T09:06:27.030-07:002009-10-28T09:06:27.030-07:00Dan, thanks for that clarification!
So, could som...Dan, thanks for that clarification!<br /><br />So, could someone else estimate their wattage by using the following equation?:<br />Your Watts = DC's Watts x [(Your system weight/DC's system weight)/(Your time/DC's time)]phippshttp://www.blogger.com/profile/02117172371253313913noreply@blogger.com