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]

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.

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]

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

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]

How did you do this? did you go to that analytic site and punched some numbers (thumbs up for your)?

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]

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.

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]

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.

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]

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!

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]

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.

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]

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).

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

 

[2laps]

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.

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'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.

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]

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

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

 

[frenchyge]

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 .

Keep in mind that that mere 1m/s constitutes a 33% increase in speed when going from 3 --> 4 m/s. That's why small differences in rider power really show themselves when the race goes uphill.

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

At least you're familiar enough now to run some "what ifs." That really is a great site -- www.analyticcycling.com

 

[frenchyge]

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

Another way to say it is that gearing doesn't affect the power required to climb, if the speed is held constant. What changes is the cadence of the pedals and the force required to push them down each time (ie, spinning easily or mashing).

The way I think of it is that lower gearing allows you to climb *slower* (ie, with less power) while still maintaining a comfortable cadence which doesn't kill the knees. After all, the reason we have low gears is because we lack the power needed to fly up some hills.

 

[2laps]

Keep in mind that that mere 1m/s constitutes a 33% increase in speed when going from 3 --> 4 m/s. That's why small differences in rider power really show themselves when the race goes uphill.

At least you're familiar enough now to run some "what ifs." That really is a great site -- www.analyticcycling.com

Your wright frenchyge, going from 3 to 4 doesn't seem much but infact it does constitutes a 33% increase in speed. It seems i overlooked that one.

I now have downloaded a profile from the Mont Ventoux the southern approach. I have a new problem !
How would i simulate this route on my tacx flow trainer. I can not program this trainer, what i can do, is changing the needed power on a given time.
The profile is devided in segments of a 1000m each with the slope.
Should i calculate the power needed for each segment keeping my speed constant and change that power every 330sec (if i want my speed at 3m/s)??

 

[frenchyge]

That should work to simulate the actual ride on your trainer. You can asume 3 m/s and determine the power requirement for each section based on that speed, but what's really going to happen on your ride is that your speed will naturally vary depending on the steepness of each road section, right? In other words, if there's a very steep section of road, then you wouldn't blow yourself up trying to maintain 3m/s, you'd crawl up at whatever speed you could manage given the power you had available. So, when you calculate the power requirement for each 1000m section of road, place a limit on how much power you're willing to expend. If the required power at 3 m/s exceeds that limit on certain sections, then calculate the max speed on those sections based on your power limit, and adjust those particular interval durations based on riding 1000m at that new, calculated max speed (ie, 400 sec at 2.5m/s, 500 at 2m/s).

That seems pretty complicated, but hopefully you can save your power profile once you've built it. That'll certainly give you a nice benchmark ride to test yourself. I don't have those capabilities on my trainer, so the simpler approach I'd take is to just ride long intervals above the average power needed for the ride (235W, in your case) in hopes of raising my 2 hr power as high as possible. If you can't hold 235W for 2 hrs, then that just means you'll climb a little slower during your ride. You'll still make it to the top. The only thing to worry about is having too little power to climb at a pace that maintains a comfortable cadence given your gearing. That's what will shut you down.

 

[rikoshea]

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.

---------------------------0----------
You will need to average ~190W for two hour

I am assuming that you are starting from Bedoin. Which is the hardest side - and the the one that you should do .

The road surface is fairly good and rolling resistance isn't an issue at the speed you will be going at anyway. You're biggest problem is your gearing; with a low of 39-21 you are going to be in big trouble unless you like to climb out of the saddle A LOT! Your cadence at this speed would be less than 50 rpm. There are two very hard sections over 10% which at this speed would require a 280 W effort - more realisticly you would need to travel at 7.5 km/h on these sections and with you current gearing would require a cadence of 32 rpm.

So to summarize, you need either a triple or a 32 cog or a pair of comfortable cycling shoes (for walking). 190 W for two hour will do OK.

Here are the details:

Input Parameters
================
Cyclist
-------
Height [m] ............................. 1.72
Mass [kg] .............................. 64.00
A (Frontal area) [m^2] ............ 0.4392
A as % BSA ........................... 25.00
CD (Drag coefficient) ............... 0.850
CDA [m^2] ............................ 0.3733

Course
------
Velocity [km/h] ........................ 11.350
Distance [km] .......................... 22.7
Time [h:m:s] ........................... 2:0:0
Slope (%) (Rise/run * 100) ........ 7.1
Wind Vel [km/h] ........................ 0
Wind Angle [0-180 degree] .......... 0
Altitude [m] (average)................. 1000
Acclimatized .............................. No

Atmosphere
-----------
Sea Level Corrected Air Pressure [mb] .. 1013.25
Air Pressure [mb] ...................... 901.16
Relative Humidity (%) .................. 55.00
Air Temp [deg C] ....................... 15
Air Density [kg/m^3] ................... 1.0852

Equipment
---------
Bike+Clothing Mass [kg] ................ 9
Drive Efficiency (%) ................... 97.50
Crr (Rolling resistance coefficient) ... 0.0045
Chainring (teeth) ...................... 39
Cog (teeth) ............................ 21
Wheel Circumference [mm] ............... 2096
Cadence (Rev/min) ...................... 48.6


Results
=======
Mechanical Power
----------------
Total [W] .............................. 181.3
Air Resistance [W] ................... 6.3 3.5%
Rolling Resistance [W] .............. 10.2 5.6%
Slope Resistance [W] ................. 160.2 88.4%
Drive Train [W] ........................ 4.5 2.5%

Power/Mass [W/kg] ...................... 2.83
Power/CDA [W/m^2] ...................... 486

Sea Level Aerobic Power
-----------------------
Total [W]............................... 190.8

Available Aerobic Power (%) ............ 95.0

Power/Mass [W/kg] ...................... 2.98
Power/CDA [W/m^2] ...................... 511

Energy Requirements
-------------------
Total [kjoule] ......................... 1864
Cycling [kjoule] ....................... 1304
Basal [kjoule] ......................... 559

 

[rikoshea]

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.

---------------------------0----------
You will need to average ~190W for two hour

I am assuming that you are starting from Bedoin. Which is the hardest side - and the the one that you should do .

The road surface is fairly good and rolling resistance isn't an issue at the speed you will be going at anyway. You're biggest problem is your gearing; with a low of 39-21 you are going to be in big trouble unless you like to climb out of the saddle A LOT! Your cadence at this speed would be less than 50 rpm. There are two very hard sections over 10% which at this speed would require a 280 W effort - more realisticly you would need to travel at 7.5 km/h on these sections and with you current gearing would require a cadence of 32 rpm.

So to summarize, you need either a triple or a 32 cog or a pair of comfortable cycling shoes (for walking). 190 W for two hour will do OK.

Here are the details:

Input Parameters
================
Cyclist
-------
Height [m] ............................. 1.72
Mass [kg] .............................. 64.00
A (Frontal area) [m^2] ............ 0.4392
A as % BSA ........................... 25.00
CD (Drag coefficient) ............... 0.850
CDA [m^2] ............................ 0.3733

Course
------
Velocity [km/h] ........................ 11.350
Distance [km] .......................... 22.7
Time [h:m:s] ........................... 2:0:0
Slope (%) (Rise/run * 100) ........ 7.1
Wind Vel [km/h] ........................ 0
Wind Angle [0-180 degree] .......... 0
Altitude [m] (average)................. 1000
Acclimatized .............................. No

Atmosphere
-----------
Sea Level Corrected Air Pressure [mb] .. 1013.25
Air Pressure [mb] ...................... 901.16
Relative Humidity (%) .................. 55.00
Air Temp [deg C] ....................... 15
Air Density [kg/m^3] ................... 1.0852

Equipment
---------
Bike+Clothing Mass [kg] ................ 9
Drive Efficiency (%) ................... 97.50
Crr (Rolling resistance coefficient) ... 0.0045
Chainring (teeth) ...................... 39
Cog (teeth) ............................ 21
Wheel Circumference [mm] ............... 2096
Cadence (Rev/min) ...................... 48.6


Results
=======
Mechanical Power
----------------
Total [W] .............................. 181.3
Air Resistance [W] ................... 6.3 3.5%
Rolling Resistance [W] .............. 10.2 5.6%
Slope Resistance [W] ................. 160.2 88.4%
Drive Train [W] ........................ 4.5 2.5%

Power/Mass [W/kg] ...................... 2.83
Power/CDA [W/m^2] ...................... 486

Sea Level Aerobic Power
-----------------------
Total [W]............................... 190.8

Available Aerobic Power (%) ............ 95.0

Power/Mass [W/kg] ...................... 2.98
Power/CDA [W/m^2] ...................... 511

Energy Requirements
-------------------
Total [kjoule] ......................... 1864
Cycling [kjoule] ....................... 1304
Basal [kjoule] ......................... 559