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assuming all your power is going to moving you upward (increasing potential energy), then it would be just Mg(VAM) where M is mass (in Kg), g is gravity (~9.8 m/s^2) and VAM is vertical ascent speed as you said, in meters/second.

How good of an assumption is it that all your power is going to climbing? For climbing off road, you aren't going fast enough that you need to consider wind resistance. Rolling and bearing fiction... I doubt they are trivial, but good luck trying to estimate them.

I'd guess though that you don't have an accurate way of measuring VAM, you can average it over a climb, if you had a good altimeter or good elevation data, but you can not measure it instantaniously. For averaging it over a climb I'd guess the inaccuracies from ignoring friction are probably less than the inaccuracies in elevation data or timing.
 

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Discussion Starter · #3 · (Edited)
I think there must be a friction / air resistance and gradient correction and so on fudge factor in there.

For Basso

est. wt = 67 kg
bike wt. at UCI minimum = 6.8 kg
shoes / clothes est 1kg

VAM 1820 m/hr as stated here: "On the tough Colle di San Carlo (10.5km at 9.8%) Ivan bettered himself: VAM = 1820m/h, equal to 6.27 w/kg, notwithstanding the rainy conditions and the almost 2000m of altitude."

ref here: http://www.53x12.com/do/show?page=indepth.view&id=75

Anyone know the answer to this riddle?

EDIT: ... oh .... here is one ...
http://www.cycle2max.com/c2m/c2max.nsf/documents/CE3788BFC597D7F3E925717C0031CDD0?OpenDocument
 

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keep in mind that Basso is climbing fast enough that it might not be proper to disregard aerodynamic drag - you or me climbing our favorite trail are not. I also do not believe that number to the sig figs stated: you would need an altitude-corrected drag coeficent, you would need to know how much additional weight he had picked up due to wet clothes, you would need to know wind speed and his heading relative to it (which changes so much you can't really draw anything meaningful from it).

from that link: "The formula is very accurate on a steady climb with no flat spots on a wind free day, provided the ascent is known accurately." Unfortunately this situation does not exist in real life, and the result of that formula is of very limitied value. This formula does not account for any energy loss other than aerodynamic drag (neglecting rolling resistance is of course more appropriate on a road bike than a MTB). Using a 0.29 drag coeficent is not appropriate for all riders all the time.

This process is basically what that iBike thing is supposed to do. Every time I've seen it mentioned I see a hundred replies on how stupid it is. Granted, most of those are fairly uninformed opinions, but no one seems to think it's worthwhile backing into power from this kind of data.
 

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Discussion Starter · #5 ·
Joules said:
keep in mind that Basso is climbing fast enough that it might not be proper to disregard aerodynamic drag - you or me climbing our favorite trail are not. I also do not believe that number to the sig figs stated: you would need an altitude-corrected drag coeficent, you would need to know how much additional weight he had picked up due to wet clothes, you would need to know wind speed and his heading relative to it (which changes so much you can't really draw anything meaningful from it).

from that link: "The formula is very accurate on a steady climb with no flat spots on a wind free day, provided the ascent is known accurately." Unfortunately this situation does not exist in real life, and the result of that formula is of very limitied value. This formula does not account for any energy loss other than aerodynamic drag (neglecting rolling resistance is of course more appropriate on a road bike than a MTB). Using a 0.29 drag coeficent is not appropriate for all riders all the time.

This process is basically what that iBike thing is supposed to do. Every time I've seen it mentioned I see a hundred replies on how stupid it is. Granted, most of those are fairly uninformed opinions, but no one seems to think it's worthwhile backing into power from this kind of data.
I've done some more googling and reading .... and bear in mind that I am only interested in maybe a +/- 5% accuracy .... ballpark is close enough.

Let's assume a road bike for power measurement.

The rolling resistance of a road bike is very small. You can almost discount it.

The winds speed (headwind and uphill speed) is small but must be accounted for a bit. Below 16 km / hr the aero effect is very small ...

Comments: the only thing that really matters is your time up the hill; still I think it is fun to get a rough estimate of power and watts per kilogram

It also would be fun to watch you watt/kg "change" if you were on a weight loss program; and then relate that to your *hopefully* increased uphill speed.

Still, I would love to know the coeff Dr. Evil plugs in to get his numbers.

Yes, Basso climbs so fast that aero drag MUST be accounted for. ... I read somewhere he was climbing the switchbacks so fast in the Giro that he had to momentarily stop pedaling to balance the bike through the turn.
 

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Wasatch Walt said:
As Dr. Evil (Dr. Ferrari) shows; you can know a riders weight ... and their VAM (vertical ascent speed in meters) and calculate their watts per kilogram.

Can somebody show me the step by step calculation to do this? I am enough physics and math challenged to not get it.

Then I can hopefully do my own Q&D watts/kg calc for myself.

Thanks

Here are some references:
http://www.53x12.com/do/show?page=indepth.view&id=75
http://www.53x12.com/do/show?page=article&id=48
Or go to www.analyticcycling.com and plug your numbers into their online calculator and have it do the math for you.
 

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I have a spreadsheet that helps develop these calculations. I would post if I knew how.

The sheet includes rolling friction wind friction mechanical efficiency, elevation, speed and time.

I took it ffrom SRM german power meter manufactures.
 
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