Mont Ventoux Power calculation

2laps

I would like to train for climbing the Mont Ventoux and i would like to do it in about 2hours. Now i have a tacx flow trainer wich gives me a watts indication. I would like to know how much watts i have to produce for about 2hrs to climb the Mont Ventoux. I already went to the analytic.com site, but i don't understand half of it. Some figures: i weigh 64Kg; height: 1m72; Bike weight : +- 7Kg; gears:11-21/39-53; distance +- 20Km and slope avg 8-9%

Can someone pls give me a straight forward answer on this.

matteobma

Hello 2laps,
Assuming an avg speed of 10 Km/h, tot weight of 75kg (bike+you+drink&food) and avg slope 8.5%, and cx 0.0021 and asphalt in good conditions, you need supply 198.5 W (avg) for 2 hours.

Have a nice ride !!!
Ciao Matteo

2laps

Wow, tks this is what i was looking for. So if i can hold an output of +- 200 W during 2 hrs i will be able to climb this mountain.
How did you do this? did you go to that analytic site and punched some numbers (thumbs up for your)?

matteobma

pW=avg power in watt
P=Tot Weight: bike+biker,accessories
p=slope/100 (es: 10,5% = 0,105)
a=attrition: = 0,01 asphalt in good conditions
KS=cx avg = 0,021
v=speed in mt/second (dist in meter/time in second; or km (hours)/3,6; es: 36km/h /3,6=10 m/s)
9,81= costant for conversion chilogrammeter to Watt

The calc formula is:

pW=[[P*(p+a)+(KS*v*v)]*v]*9,81

ex: biker of 75 kg + bike 10 kg slopel 10% at speed of 3 m/s.
[[85(0,1+0,01)+(0,021*3*3)]*3]*9,81=[(9,35+0,189)*3]*9,81=28,617*9,81 = 280,73 W

if you are friendly with excel you can easy do it !

This and many other calc info (in italian language) you can find at: http://freeweb.supereva.com/pianetaciclismo/index.html

I hope can be helpful...
Caio Matteo

frenchyge

On www.Analyticcycling.com, start at the gears/speed/cadence link. Using your lowest gear of 39x21, and a cadence of 60 (basically, enter the minimum that is comfortable), you'll be climbing at 4.08 m/s (14.7 kph). Take that number to the Static Forces on Rider --> Power, given Speed link. Using the default frontal area and drag coefficient, the 1500m elevation air density, .085 slope, 72kg, asphalt road rolling resistance, and 4.08 m/s speed, I get 265W required.

If 265W is more than you're comfortable with, then go to "Speed, given Power" and use your 2hr power to find the speed that you could hold for the climb. Then take that speed back to the Gears & Cadence section to determine the gearing that you'll need to climb that speed at a comfortable cadence.

This doesn't dispute the 200W figure given previously, but shows that climbing at 10kph with your gearing might be a painfully low cadence for that climb. I get 41 rpm in that case using a 700cm wheel.

acoggan

At first blush, the difference would seem to be in the assumed rolling resistance...a CRR of 0.001 is much closer to what you'd expect on a board track than on an asphalt road. But, maybe Mont Ventoux is "paved" with wood to make the ascent easier for cyclists!

acoggan

Oops, sorry - I see now that you calculated the power required to climb at a cadence of 60 rpm in a 39x21, which would get you to the top in significantly less than 2 h. Still, I think the 200 W value is an underestimate, because rolling resistance will be significantly higher than assumed.

frenchyge

The power req'd is 256W if they've retrofitted Ventoux with a wooden bike lane (CRR of .001 vs .004).

Alternately, if the road is rough pavement (vs. smooth asphalt) then the power req'd is about 277W (CRR of .008).

mattv2099

Ventoux was repaved right before the 2004 dauphine libre (spelling???). It's supposed to be in excellent condition.

2laps

Much appreciate it. I will have another go at analyticcycling and try to do what you are telling me now. In any case it seems i have a lot of training todo.

2laps

After being pointed out in the right direction by 'frenchyge' at analyticcycling i found out that the most significant factor in the calculations was the speed factor. If i wanted to climb at a speed of 3m/s i would need approx 200W, if i would climb at a speed of 4m/s i already need +- 270 W. a whopping +30% increase for a merely 1m/s . The watts dont change that much if i altered to sealevel, or if i added some weight. Even if i changed the slope to 0.10 and hold the speed at 3m/s i still got less than 270W (+-235W).

I think this will be my target -> holding a 235W output for about 2hrs

prometeus

I'm just starting out with biking (so maybe dont take it seriously) but from what I hear is that you need def a 39/23 for getting on top of the ventoux... The guys in the Tour de L(Fr)ance even have it mounted the some slower climbers that is.

2laps

I agree, i was even thinking of changing the last gear in a 26 or even a 28.
The point is that whatever gear you use, the avg power(Watt) you need to get to the top stays the same and the gear you use only devides that power you need per revolution. So with a small gear(21) you need less revolutions but with a higher wattage and with a gear of(26) you need more revolutions with a much less power output. tell me if i'm wrong

matteobma

Yes, ..a little bit confusion.
You need the same power !!! (It not depend by gear) but if you you use a big gear(26-28) you need to apply less force (Newton) on your pedals! ...the total amount of power, you must supply to rise the top, is the same!

Ciao Matteo