Quoted post said:Originally posted by james.dippel
...Would you mind giving me your calculations for Wattage output? If it really is about 600W then I would be putting out 8.9W/KG, which I'm informed is quite a figure.
Many thanks.
Ric's undoubtedly given a more accurate figure. All I did was work out the power required to overcome gravity, which you can calculate as :
M * g * v * r
where
M = mass of rider + bike (kilograms) = (guess) 65 + 9 = 74 kg
g = gravitational acceleration at earth's surface = 9.81 m/s/s
v = speed (metres / s) = 13 * 1600 / 3600 = 5.78 m/s
r = gradient = 0.144
yielding
Power (climb) = 74 * 9.81 * 5.78 * .144 = 604 watts
In addition to this, as Ric's calculation shows, there are some watts needed to overcome air resistance, rolling resistance etc.
If your 720i and the PPP software is saying 14.4% then I think your altitude readings are haywire for some reason. If it was the distance measurement (eg setting up the wheel circumference way too large) you'd also be seeing impossibly high speeds on the flat. You could double check this by using the following alternative formula for power which doesn't depend on gradient or speed:
P (climb) = altitude gain (metres) * M * g / climb time (seconds)
If your 600+ watt figure were right (which it obviously cannot be, as per Ric's note), then given it took you 315 seconds to climb the hill, the height gain would be 260 m or 853 feet. Assuming you're putting out a somewhat less superhuman figure of 350 watts (still pretty damn good), the height gain would be less than 150 m / 500 ft.
One final thought - you're not by any chance calculating gradient using different units for height gained vs distance travelled?