Ah, so THAT'S what's holding me back!

[Jeremy McCreary]

 

[PDoz]

Nah, it's geography - I'm still looking for that 60 km downhill track

 

[Jeremy McCreary]

Nah, it's geography - I'm still looking for that 60 km downhill track

You mean one that's downhill all the way around? I hear there's one in Escherville.

 

[dodgeman]

With my college degree I had a lot of physics and a class in dynamics. One thing you learn is something that is linear versus something that isn’t. If you pick up 100 pounds and carry it 20 feet and then carry it 40 feet it takes roughly twice the energy to go an extra 20 feet. Wind resistance doesn’t work that way, it’s roughly based on the square of your speed. You go twice as fast, the wind resistance is 4 times greater, go three times faster the wind resistance is 9 times greater. That’s something the human body is up against, even trying to be as aerodynamic as possible.

 

[Chargeride]

I did a 31.30 10 mile time trial at 17 on a pretty standard steel bike running tubs.
I trained for it and was so hyped, the first five miles I felt like I was being pushed by a car.

Its not bad for someone who didnt race and just mainly rode weekends on 100 mile rides at a steady slow pace.

 

[Jeremy McCreary]

With my college degree I had a lot of physics and a class in dynamics. One thing you learn is something that is linear versus something that isn’t. If you pick up 100 pounds and carry it 20 feet and then carry it 40 feet it takes roughly twice the energy to go an extra 20 feet. Wind resistance doesn’t work that way, it’s roughly based on the square of your speed. You go twice as fast, the wind resistance is 4 times greater, go three times faster the wind resistance is 9 times greater. That’s something the human body is up against, even trying to be as aerodynamic as possible.

Agree. The video emphasized power output, and things are even worse by that measure.

On hard, smooth, level ground in still air, as in a one-hour, total resistance (R, a force in Newtons) is roughly

R ≈ Ka Vg² + W Crr,

where Ka is the drag constant (in kg/m) for a given bike, rider, and posture, Vg is ground speed in m/s, W is bike+rider weight in Newtons, and Crr is the coefficient of rolling resistance (no units). This makes resistance quadratic in ground speed.

The rider power P in Watts needed to overcome R at constant Vg is then

P = R Vg ≈ Ka Vg³ + W Crr Vg,

which makes power cubic in ground speed.

At 59 kph (16.4 m/s), P ≈ 443 W for pro-level values of Ka, W, and Crr. And 99.5% of it is aerodynamic. To go 60 kph, you'd have to come up with 22 W more. Huge barrier over a 1 hr period.

 

[mschwett]

Agree. The video emphasized power output, and things are even worse by that measure.

On hard, smooth, level ground in still air, as in a one-hour, total resistance (R, a force in Newtons) is roughly

R ≈ Ka Vg² + W Crr,

where Ka is the drag constant (in kg/m) for a given bike, rider, and posture, Vg is ground speed in m/s, W is bike+rider weight in Newtons, and Crr is the coefficient of rolling resistance (no units). This makes resistance quadratic in ground speed.

The rider power P in Watts needed to overcome R at constant Vg is then

P = R Vg ≈ Ka Vg³ + W Crr Vg,

which makes power cubic in ground speed.

At 59 kph (16.4 m/s), P ≈ 443 W for pro-level values of Ka, W, and Crr, and 99.5% of it is aerodynamic. To go 60 kph, you'd have to come up with 22 W more. Huge barrier over a 1 hr period.

yep. (close to) cubed. physics is a harsh mistress.

luckily energy to travel a given distance is closer to squared at twice the speed since the time you’re expending that much-greater-level-of-energy is thankfully half as long

an interesting (to me) personal anecdote. since my reappearing health issues, i’ve kept my cycling average power output for a ride to 150w, instead of 200w (sometimes more) previously.

those old rides on the same routes at 200w average were more than 1/3 more average power - but only 2-3mph faster. a ride which was all climbing would show a bigger difference, but also keeping it to around 1,000 feet of climbing per 20 mile ride.

 

[Jeremy McCreary]

yep. (close to) cubed. physics is a harsh mistress.

luckily energy to travel a given distance is closer to squared at twice the speed since the time you’re expending that much-greater-level-of-energy is thankfully half as long

an interesting (to me) personal anecdote. since my reappearing health issues, i’ve kept my cycling average power output for a ride to 150w, instead of 200w (sometimes more) previously.

those old rides on the same routes at 200w average were more than 1/3 more average power - but only 2-3mph faster. a ride which was all climbing would show a bigger difference, but also keeping it to around 1,000 feet of climbing per 20 mile ride.

Glad to hear that you can take care of yourself at only 2-3 mph slower. Which dream bikes are you riding now?

 

[mschwett]

Glad to hear that you can take care of yourself at only 2-3 mph slower. Which dream bikes are you riding now?

i’m back to the non-electric s-works aethos for most fully recreational rides, but i ride the scott addict e-ride for more ambitious rides, whenever time is of the essence or i’m not feeling great, and at times of day when meds are not fully effective.

it’s a far cry from the adventure of 60-100 miles rides off into the distant hills, but trying to see the positives.

 

[Jeremy McCreary]

i’m back to the non-electric s-works aethos for most fully recreational rides, but i ride the scott addict e-ride for more ambitious rides, whenever time is of the essence or i’m not feeling great, and at times of day when meds are not fully effective.

it’s a far cry from the adventure of 60-100 miles rides off into the distant hills, but trying to see the positives.

No wonder you like the Aethos. Quite a design project.

Aethos Innovation

www.specialized.com

 

[PedalUma]

Aero things are fuzzy. birds' feathers, a moths' wings under a microscope, sharkskin in the water, a bumble bee. Most of that stuff in the video was shinny and less aero. Do not shave your legs if you want to go faster. Golf balls with dimples go farther that those that are smooth. A lightly sanded golf ball goes even further. A new record will be hit when the bike has velvety finish on it that is soft to pet. I ride faster in a cashmere sweater than a Specialized jacket. Nature knows. It is all about causing random and slippery micro-turbulence at the surface. The Aethos is not gloss. I wonder why.
Moth Fly Example: https://murry-gans.blogspot.com/2014/02/moth-fly-in-mens-room.html

 

[fooferdoggie]

the best I ever did was average 205 watts over 16 miles I think fetching some bbq. Now I seldom get over 130 watts

 

[mschwett]

the best I ever did was average 205 watts over 16 miles I think fetching some bbq. Now I seldom get over 130 watts

food can be a strong motivator lol.

i think my best hour was probably 240 watts or so, best 3 hours without stopping around 210. best 6 with one stop probably not quite 200. but it's interesting to think that the capacity of an average human over a couple hours is similar to a large ebike battery!

 

[mschwett]

No wonder you like the Aethos. Quite a design project.

Aethos Innovation

www.specialized.com

it's a really nice bike. easy to get lost in the minor fussy details and traditions of road bikes (of which i have no historical nostalgia!) but there certainly are some intangibles about a bike like the aethos that can't be fully explained by weight, aerodynamics (or the lack thereof!) and so on. it's sublime in a very subtle way.

 

[gromike]

I think if I want to pedal fast that I'll stick with my $100 Roubaix.

Fastest pedal bike I ever rode, though it's geared too high for my right knee. Decent pedals would cost more than the bike, and, as such, she sits an object d'art.

 

[Stefan Mikes]

luckily energy to travel a given distance is closer to squared at twice the speed since the time you’re expending that much-greater-level-of-energy is thankfully half as long

I can see some error in this reasoning. The energy spent would be indeed lower if you rode a given distance twice as fast but that would not cancel the third power term for the power demand.

I'd like to see some numbers to prove the energy spent on a very fast ride is closer to the square term.

 

[Chargeride]

The effort of dealing with the terrain is more than any pedalling I do, Stefan often ribs me for using a throttle, but it has the effect of requiring more effort to deal with the physics of balance and impact.
I'm quite often exhausted without using the cranks once.
I'd need a full body watt meter

Its the reason why motorcross was deemed the most strenuous sport by the California National Athletic Health Institute.

 

[Stefan Mikes]

The effort of dealing with the terrain is more than any pedalling I do, Stefan often ribs me for using a throttle, but it has the effect of requiring more effort to deal with the physics of balance and impact.
I'm quite often exhausted without using the cranks once.

And just think Charge how many people in Europe ride rough trails without any throttle
You could be wearing a wrist HR monitor such as Polar OH-1 to determine your actual effort.

 

[6zfshdb]

Just use an e-bike. Problem solved.

 

[antboy]

Aero things are fuzzy. birds' feathers, a moths' wings under a microscope, sharkskin in the water, a bumble bee. Most of that stuff in the video was shinny and less aero. Do not shave your legs if you want to go faster. Golf balls with dimples go farther that those that are smooth. A lightly sanded golf ball goes even further. A new record will be hit when the bike has velvety finish on it that is soft to pet. I ride faster in a cashmere sweater than a Specialized jacket. Nature knows. It is all about causing random and slippery micro-turbulence at the surface. The Aethos is not gloss. I wonder why.
Moth Fly Example: https://murry-gans.blogspot.com/2014/02/moth-fly-in-mens-room.html

Aero-Fur 3000.