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% increases in power required to improve average TT speed

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% increases in power required to improve average TT speed

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25-06.-2005, 01:26 PM

#61

SF Bay Triathlete

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Join Date: Apr 2005

Location: SF Bay Area (East Bay)

Posts: 9

Re: % increases in power required to improve average TT speed

Quote:

Originally Posted by robkit

imagine a flat, windless TT course of 1O or 25 miles and that a rider needs to produce X constant watts to finish in a time equivalent to average speed 20mph.

obviously X is a function of frontal area, drag, rolling resistance, etc, but in relative terms does anyone have estimates of the factors of X required to increment for each successive 1mph, upto say 30mph?

i would find this very interesting, both to scope the level of curvature (ie getting from 24 to 25 requiring more power than getting from 20 to 21 due to the exponential increases in air resistance), and to figure out what sort of improvements are realistic from a given starting point.

I was a half assed mechanical engineering student 30 years ago...Here's what I recall (that's really not responsive to the orig thread...but interesting to me:

1. ever see a porche crashed on the autobaun....have you noticed how disintegrated the car looks....that's cause the stored energy in the car goes up as the square of the velocity...and of course it ain't detroit steel either...so 100 kph squared is 10000. 200 kph=40000....4x the stored energy at 2x the speed. Don't bother with a seat belt.

2. in cars....wind resistance dominates on the flat...vs rolling resistance etc...not sure what the speed vs effect is.

3. rolling resistance drops with wheel diameter...I think it's a linear function

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