Cozy Beehive wrote:...........
Overall, for the full climb, 5.8-6.0 W/kg, not more not less.
[color="Red"]Note : I answer here but I could have posted this anywhere else, it's not Cozy in particular that I address.
Copied from my TOURMALET WEST SIDE post
Today the stage ends at the Tourmalet.
Bottom of the climb in Luz St-Sauveur at 711m asl.
top, 18.7 km later and 1404 m. higher.
Assume no draft, a 70 kg cyclist, with 8kg equipment.
Take CdA = 0.4 m^2
assume average temperature 25°C. -> av. air density 1.03 g/cm^3.
Neglect the fact that the 1st km is not so steep . 4.5% or so.
Run various climbing speeds on analyticcycling.com
49 min : air resist = 53 watts , grav+rr = 383 W Total 436 watts
ie 6.23 watts/kg
add 2.5% for transmission loss = 6.38 W/kg
add 3% to compare with sea-level effort => 6.57 W/kg.
52 min : air res. 44 W, grav+r.r. = 361 watts total 405 watts
add 2.5% transmission -> 5.9 W/kg
add 3% to compare to sea-level => 6.07 W/kg.[/color]-----
Drafting behind one racer reduces air resistance by about 25%, a saving of 11 watts for 52 min, ie 0.16 W/kg
At 49 min, the saving is 13 watts, ie 0.19W/kg.
End of copy
Therefore, a 70 kg racer (*+8kg) would require
1314 SRM kJ to climb Tourmalet in 49 min
1295 SRM kJ to do it in 52 min.
Interpolating we get 1304 SRM kJ for 50:37
If we assume drafting for half the duration the reduction in kJ required will be 18 kJ, which gives 1286 kJ. => 423 SRM watts or 6.05 W/kg for Schlek (without altitude effect correction)
Note that this still depends on the altitude difference covered being really 1404 meters over 50:37.
COMPARISON WITH HORNER’S SRM
Now, what do we get for a 64 kg (+8kg) racer drafting for the whole 52:22 duration of the climb?
Energy expenditure for a 70 kg (+8kg) racer climbing in 52:22 no drafting => about 1295 kJ reduced to 1260 kJ if drafting the whole time.
For a 64 kg(+8 kg) racer drafting the whole time this becomes 1163 kJ
For a 65 kg(+8 kg) racer drafting the whole time this becomes 1179 kJ
Insignificant adjustements could be made for the temperature and , slightly more significant corrections should be made for the somewhat flattish first 2 km and for the CdA not scaling exactly as the weight ( but the latter would really be a nonsensical adjustment).
This 1163 kJ is to be compared with 1132 kJ registered by Horner’s SRM, an overestimation of 2.7%. But then, of course, I only know Horner’s weight from the SRM comment that 377 watts corresponds to 5.9W/kg and we don’t know about the calibration of his SRM.
Is a difference of 2.7% acceptable? Not completely because I would have expected to end up with an underestimation as some factors were not taken into account: significant speed variations in the first minutes of the climb, wet road which increased slightly the weight of the equipment (clothe, shoes). Note that with a SRM there is no need to correct for transmission efficiency.
But it’s too early for final conclusions as there are still uncertainties on the starting and finishing altitudes for that 18.6km climb. We’ll come back to this when Portoleau publishes his observations on cyclismag.
NOTE . Constructive criticism more than welcome