More from the Book of Cokeronomy

Unicycles and Equipment
1

Another training run, more or less along last week’s route, but this time in a wind strong enough for an Enterprise dinghy to have the mainsail reefed. The main part of the ride was around the main rowing lake at the National Watersports Centre, and the wind always blows along the lake, and never across it. That gives about 2.75 - 3 km of swooping downwind, and then the same distance battering into it.

Wind resistance is proportional to the square of your speed through the air. This means that riding into the wind is always going to take more extra energy than you ‘get back’ on the return leg. To be within 0.0056% of my personal best distance was a fair achievement.

But stuff all that! Here’s what you get for Cokering:
I wouldn’t bother lapping the lake time after time on a bicycle.
And I wouldn’t bother going out for a walk after work.
So not only does the unicycle give me an excuse/incentive to get exercise…
But I see herons standing by the lake, herons flying, a heron landing gracefully in the shallow water.
I see a goose with about a dozen new goslings at the side of the track. Aaah!
And swans, wild flowers, sun glinting off the water
I see a fantastic sunset…
And because I’m riding hard, and breathing hard, I get to smell the new mown grass, and the hawthorn blossom (and the glue factory :0( )
And if this sounds sentimental nonsense, bear in mind I’ve been in a badly air conditioned office, with major roadworks outside, in the middle of a building site which passes for a city, all day, talking to rude, ungrateful and dishonest customers all day, and with several colleagues off with stress (they leave the stress to be shared out amongst the survivors, of course) and 19 miles of hard Cokering in a scenic setting is a good release from that.

And because I’m at a sports centre, I get respect and encouragement from all the rowers, canoeists, cyclists, joggers, and virtually no abuse.
And all the ladies are fit and toned and wearing lycra. (Note for female readers: all the blokes are fit and toned and wearing lycra too, OK? :0) )

Now the figures:
Standard Coker, 150mm cranks, pinned platform pedals.
Timed hour, mainly on tarmac, 12.37 miles covered (123 yards short of a personal best!)
Total distance for ride:19.12 miles. Total time1:47. Average speed 10.72mph.
Top speed, 14mph (as always!?)

2

Is the National Watersports Centre that place near Thrybergh?

3

:astonished: still 150s!!! 125s are the coker cranks of the future! I only put them on when I bent my 150s and I wouldnt consider anything else (well, maybe 110s…:wink: )

What is your fastes ever recorded speed on a coker? mine is 17.5 mph. That was scary, but fun! :smiley:

4

I think that wind resistance is proportional to the cube of your speed. The power content in wind is certainly proportional to the cube of the windspeed.

5

Re: More from the Book of Cokeronomy

Baked goods notwithstanding, the fine frangrances along a pleasant unicycle route are a major bonus to the other benefits to riding. Being a city boy, I can’t actually name any of the the great smells I pass, but they are nice indeed.

Thanks for another nice write up.

Raphael Lasar
Matawan, NJ

6

  1. Thryberg is in Yorkshire, somewhere up near Roterham. The National Water Sports Centre is at Holme Pierrepont, 3 miles from Trent Bridge Cricket Ground, on the outskirts of Nottingham. What’s ‘near’? I guess there’s 2 hours’ driving in it, so i guess you mean a different water sports centre.

  2. I’m on 150s because I will be using 150s for the Red Bull, which is mostly off road. 125s are great fun on a Coker in appropriate circumstances. I think I prefer the 150s anyway.

  3. My top speed? My computer only records to the full mile an hour. The highest it’s shown (legitimately) is 14mph. Depending on whether it ‘clicks over’ just after X.99 (as I supsect) or rounds up at X.5 (which would be arithmetically conventional) my maximum speed could be as much as 14.99mph or as low as 13.5mph. I’ve been faster on 125s, but not with a speedo. I know it was faster because I couldn’t even nearly run at the speed I hit the ground.:eek

  4. Greg: My understanding is that wind resistance is proportional to the square of the speed, because it acts on an area (simplified); but the power available to be extracted from the wind (by a windmill or similar turbine) is proportional to the cube, because there is a volume of air passing THROUGH the turbine blades. Intuitively, proportional to the square feels right. otherwise I doubt I could have done tonight’s ride in the time I managed.

Just say that the wind speed was 10mph and my speed was 10mph across the ground. What units do we measure resitance in? Newtons? I’m good at general principles, but bad at accurate facts!

Assume standing still in a 10 mph wind is 1 UNIT of wind resistance.
10 mph downwind = 0 units of wind resistance.
10 mph UPwind = 4 units of resistance.

But if you’re right about the cube, rather than the square, the difference would be between 1 unit, 0 units, and 8 units. It didn’t feel like that. (Of course, it wasn’t a 10mph wind, either!)

I vaguely recall that a BIcyclist at 20mph is using 70% of his/her energy simply overcoming wind resistance, assuming a calm day.

7

Re: More from the Book of Cokeronomy

On Tue, 6 May 2003 15:08:35 -0500, Mikefule
<Mikefule.n0x7n@timelimit.unicyclist.com> wrote:

>To be within
>0.0056% of my personal best distance was a fair achievement.
It would really be an achievement if only to COPY your PB so closely.
But from these figures…
>12.37 miles covered (123 yards short of a
>personal best!)
…it appears that you were within 0.56% of your PB.

>Top speed, 14mph (as always!?)
Don’t be afraid of the Reset button. :slight_smile:

Klaas Bil - Newsgroup Addict

A snail can sleep for three years.

8

Re: More from the Book of Cokeronomy

Bah! Reefing sails is for wimps. Ignoring the fact that the first time we sailed this year the boat capsized before even leaving the shore, more wind just makes it more exciting!

Phil

  • OT, sorry…
9

Re: Re: More from the Book of Cokeronomy

Until you reef, you’re on pins-and-needles; as soon as you reef, you regret it. Unless, I imagine, you’re out at sea fighting for your life!

10

All this talk of reefer ,150mm cranks,speed.
sounds like a pow wow

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I’m right about the cube.

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You said two conflicting things about the cube, i.e. “wind resistance goes with the cube of speed” and “power goes with the cube of speed”. One of them was right. Wind resistance (i.e. a force) goes with the /square/ of speed, according to all sources I checked.

Klaas Bil

13

I stand by my original statement. I’m right about the cube.

14

http://www.smm.org/general_info/bhop/runners.html (Runners)
Because resistance is proportional to the square of the runner’s speed minus the wind, a head wind reduces a runner’s speed more than a tail wind aids it.

http://socalroadriders.org/Articles/Aerodynamics.htm (Motorbikes)
Technically speaking, wind resistance, or aerodynamic drag, increases linearly by the increase in frontal area, and by the square of the increase in speed.

www.plugitin.co.uk/aerodynamics.htm (Electric Vehicles)
Wind resistance increases as a square of speed ie. double your speed and you hit four times the resistance; triple your speed and it goes up by nine.

http://cartalk.cars.com/Columns/Archive/2002/December/01.html (Cars)
Wind resistance increases as a square of your speed.

http://ida1.physik.uni-siegen.de/menn/motion.htm (Cyclists)
The wind resistance FAir (in Newton) depends on the aerodynamic drag coefficient cw, the projected frontal area A of bike and rider (in square meters), the air density r (about 1.225 kg/m³ at sea level for 15° C), and the square of the air speed v (in m/sec). Since it is difficult to quantify the area A precisely, one associates cw and A to the effective frontal area cwA.
FAir = 0.5 ×cw×A×r×v² = 0.5 ×cwA×r×v²
The power needed to overcome the air resistance is FAir multiplied with the velocity v:
PAir = FAir×v = 0.5 ×cwA×r×v³

Need more?

Klaas Bil

15

Greg, you may or may not be right - I’d be happy to be corrected and learn from it - but confident repetition is not an argument.

I recall from when I was interested in wind and water power, many years ago, that the energy available to be extracted from the wind is proportional to the cube of the wind speed. (Similar principles apply for water and water turbines, of course.)

The explanation, which seems to make sense to me, is that a volume of air (or water) is passing through the area swept by the turbine/rotor blades. If we’re talking about volumes, it seems consistent to talk about cubes.

Conversely, all I have ever read on aerodynamics, related mainly to bicycling, is that wind resistance is proportional to the square of the wind speed. This is because the wind is pushing on a surface (an area) and not passing through the area. Intuitively, this makes sense to me.

It only matters as a point of general interest, but if I am wrong, then I’d be happy to learn why. What have I missed?

16

I’m stubborn that way.

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Yes. I always need more. I’m greedy and insatiable.

Of course you and Mike are correct about the difference between wind resistance and the power required to overcome it. We haven’t had a good, irrational newsgroup argument lately and maybe I was just yearning for one. I’ll jump at the opportunity to be irrational.

Is wind resistance really important in bicycling? It is for stress calculations for aerodynamic design. What you really feel bicycling is the power required to overcome wind resistance. In a highly simplified model it would take 8 times the power to move an object at twice the speed in still air.

You are correct that the force exerted by the air on your person is proportional to the square of your speed with respect to the wind. Standing still in a breeze you would feel that force quadrupole as the wind speed doubled. But now you are standing still and expending no power to overcome the wind.

18

Re: More from the Book of Cokeronomy

Harper wrote:

> You are correct that the force exerted by the air on your person is
> proportional to the square of your speed with respect to the wind.
> Standing still in a breeze you would feel that force quadruple as the
> wind speed doubled. But now you are standing still and expending no
> power to overcome the wind.

Speaking as a Chicagoan who has seen small women in the Loop blown backward
into buildings, I disagree.

–
“Quemadmodum gladius neminem occidit, occidentis telum est.”
– Seneca

19

I have to agree with Mikefeule on the motivations to ride, and the joys of getting out into the fresh air for some much-needed exercise, and seeing some otherwise-unseen sights.

A little about my situation:
My job is in front of a desk, at a computer. No exercise to speak of while being paid. The desk is about 12.5 miles from my house by car, but only 8.15 miles (according to my new speedo from Unicycle.com) by HPV.

HPV, you say? Well, I have to confess to riding a bike most of the time when I do ride. I want to get back into riding the Coker, but it’s a longer ride that way, and my knee wears out when I do the 16 miles at speed in one day. My bike is a Miyata, at least (Triplecross).

To ride the Coker, I have to start by getting ready to go early enough, which is the first challenge. Then I want to fix up the cycle with a better handle. Right now it’s just a new-style Miyata seat, and I feel like the handle is going to break off at any moment. I want something solid, with a variety of hand positions, to get my weight off my crotch.

I started with 125mm cranks, but didn’t like the lack of control. Now I have a pair of I think 150s on there. I wanted 140s, but I didn’t have any lying around at the time. I’ll have to see what size I finish up with.

But anyway, it’s exercise either way. I get to breathe fresh air, get “free” exercise time, and feel better when I arrive at work. My route crosses the American River. When I drive, I have to go out of my way to get to the nearest bridge. When I ride, I get to use the bike path bridge, which is right where I need it to be to work for my commute. I get about 3.4 miles of bike path as part of my commute, about 1 mile on main roads, and the rest in neighborhood streets. There are three traffic lights I may have to stop for in either direction, though not the same exact three.

Along the way, I’ve stopped to take pictures of the river looking like glass, wild turkey, and deer. I’ve seen all of those several times, plus rabbits, plenty of squirrels, and even a rattlesnake. All this California trail riding, and the first live rattlesnake I see is along the paved bike path!

I consider myself lucky to live close enough to ride to work. Especially since I can do most of it avoiding the main roads. I highly recommend it if it works for you.

20

The key issue is not power; we can assume that the rider can actually overcome the wind resistance enough to ride. The real issue is work; how much work do you have to do to maintain speed? Since work is force x distance, the issue is force, or drag, which is proportional to the square of the speed.