air resistance

Anything about Power (watts)

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kenl
Posts: 36
Joined: Mon Dec 11, 2006 12:18 am
Location: UK

air resistance

Post by kenl » Tue Jan 16, 2007 1:06 am

Hi, I am a newbie around here since I only purchased a fortius a month ago. I have spent most of that time in the Alps!

However, yesterday I took my bike out on a real road and even a slight breeze felt like a gale. Sorry if this has been asked before, but when I am riding along the flat section of road at the bottom of L'Alpe d'Huez what assumption is the fortius software making about the resistance of the air when it calculates power and speed please?

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qcscmh
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Post by qcscmh » Tue Jan 16, 2007 1:18 am

From what i assume power would be calculated from the roller speed, the roller speed would be govered by the braking force applied which will be dependant on the riders weight, slope, and calibration.

I would therefore think that air resistance would be allowed for as a factor of the riders weight. Heavier riders have more air resistance.

Dont know which formulae they used or whether it assumes an upright aero rider position.

I dont think any information is available on any formulae for speed calculation.

kenl
Posts: 36
Joined: Mon Dec 11, 2006 12:18 am
Location: UK

Post by kenl » Wed Jan 17, 2007 8:27 pm

Thanks. Yes, it seems reasonable that the braking force includes allowances for slope, friction and drag and drag could depend on the type of bike, but perhaps that is one for the future. I am not sure I have the tyre pressue/roller set up sussed yet!!

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