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  1. #1
    rugged individualist wphamilton's Avatar
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    Waving, drag revealed!

    It comes up with such frequency, and is debated with so much passion, that it may be one of the most important questions in the sport of cycling, yet no one has really examined it scientifically. Until now.

    The roadie in full regalia, his steely gaze is focused and intent, you give a wave and you're ignored. What's up with that? Would it really hurt him to wave? That's usually a rhetorical question but I set out to find an answer. What does it cost him to wave?

    So I took my road bike to a local hill to perform some coast-down tests while simulating a roadie in training. I selected a hill with a relatively gentle grade so that speeds would be similar. In half the tests I coasted in a regular roadie position, and in half I waved all the way down while trying to maintain the same position. I wanted to make the simulation as real as possible so I wore an actual jersey, tight, and spandex cycling shorts. Helmet, sunglasses. All tests were with hands on the hoods (since careful observation has indicated that training roadies ride on the hoods, or with the same back angle while in the drops).

    This is the test rig: bike.jpg bike.jpgalthough it's Fredded up it is, as you can see, a road bike with standard road bike geometry, normal saddle to bar drop, 700x25c tires.

    To complete the simulation I strapped on a HR monitor and also turned on Strava, as if I were doing hill repeats. For you doubters out there Bike Ride Profile | Coast-down test repeats near Alpharetta | Times and Records | Strava although I didn't use Strava data since my flight recorder box is more accurate. I did three tests coasting, three waving, with no pedaling at any time. Except uphill of course. I started each test at precisely the same point in the road, with the magnet positioned 1/8th of a wheel behind the sensor.

    I threw the second waving run out because passing traffic distorted the data. The final repeat in Strava was not a test run - I just did it because just coasting is pretty boring. Here is the result:
    roadie_vs_waving.jpg
    The vertical axis is miles per hour, the horizontal is units traveled (unit representing approximately 7 feet, one wheel revolution)

    It's pretty clear that waving costs a significant amount of speed, presumably by adding drag. If we need a number, how much drag, here is a real general estimate. Assuming that the highest speed is the terminal velocity for that grade and object (I haven't proven that, but I've been up and down that hill a lot and it is or is close to) then the drag force is equal to the force of gravity. The force of gravity is the same for both roadie and waving, and therefore the ratio of CdxA (Coefficient of drag times area) is the inverse ratio of squared velocities. From the basic drag equation.

    In this case, that comes to about 12% greater drag created by waving. So there you have it: drag is increased by 12% when he waves.
    Last edited by wphamilton; 06-28-14 at 02:30 PM.

  2. #2
    Senior Member bhchdh's Avatar
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    "In half the tests I coasted in a regular roadie position, and in half I waved all the way down while trying to maintain the same position."

    Good information, but who waves the whole time they are riding ?

  3. #3
    Senior Member Northwestrider's Avatar
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    Nice, but I'm more of a Fred than roadie, so what would I know.

  4. #4
    rugged individualist wphamilton's Avatar
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    Quote Originally Posted by bhchdh View Post
    "In half the tests I coasted in a regular roadie position, and in half I waved all the way down while trying to maintain the same position."

    Good information, but who waves the whole time they are riding ?
    No one does, but that's how you test things. Keep the testing variable constant throughout the test duration.

    BTW, I felt like a lunatic waving my arm around while coasting down the hill at 26 mph.

  5. #5
    Senior Member bhchdh's Avatar
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    Quote Originally Posted by wphamilton View Post
    BTW, I felt like a lunatic waving my arm around while coasting down the hill at 26 mph.

  6. #6
    Senior Member CactoesGel's Avatar
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    Entertaining experiment!

    I lived in Charlotte for 2 years. In my first week there, I learned that waving was a thing. I liked it, people made you feel welcome. I moved back to SoCal and tried waving at people. They just look at me like I am crazy LOL

    I wave anyway even if they don't wave back

  7. #7
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    What if instead of waving with your whole hand, you wave with only one finger?

  8. #8
    Senior Member Homebrew01's Avatar
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    Conclusion: Waving is a drag.
    Bikes: Old steel race bikes, old Cannondale race bikes, less old Cannondale race bike, crappy old mtn bike

  9. #9
    Senior Member yote223's Avatar
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    Simple entertainment for simple......

    P.S Don't forget to factor in the rotation of the Earth and the gravitational pull of the Moon.
    It's hard to soar with the Eagles when you're flying with Turkeys
    Charter Member of PSIP Coalition.

  10. #10
    Fresh Garbage hairnet's Avatar
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    I wave with a snarl

    Quote Originally Posted by Scrodzilla View Post
    I'd rather ride a greasy bowling ball than one of those things.
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  11. #11
    Rubber side down Clipped_in's Avatar
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    Quote Originally Posted by profjmb View Post
    What if instead of waving with your whole hand, you wave with only one finger?
    I can't say about drag, but has been known to cause a major drop in approval ratings...

    ...Just mount a bicycle and go out for a spin down the road. ~ Sir Arthur Conan Doyle

  12. #12
    rugged individualist wphamilton's Avatar
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    Quote Originally Posted by hairnet View Post
    I wave with a snarl

    And well you should, knowing now that it increases your drag by 12%!

    Quote Originally Posted by yote223 View Post
    Simple entertainment for simple.....P.S Don't forget to factor in the rotation of the Earth and the gravitational pull of the Moon.
    Possibly the most important question of the sport judging by the number of threads on the subject. These results are not only significant, they are historic even if I do have to say so myself.

    Centripetal force at the equator is approximately 1/289 of the force of gravity. Since the difference in velocities between the two conditions (traveling counter rotation) is approximately .0014 that of the Earth's rotation, and since the centrifugal force varies with the square of rotational velocity, the difference in force is 2 times ten to the minus 6 power, corresponding therefore to about 7 time 10 to the minus 9 power fractional of g, and thus disregarded as insignificant.
    Last edited by wphamilton; 06-28-14 at 04:15 PM.

  13. #13
    Stand and Deliver FLvector's Avatar
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    And here I thought this is where the thread was going.......

    1305573409-lmhm_btwd2011_6.jpg

  14. #14
    rugged individualist wphamilton's Avatar
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    Quote Originally Posted by FLvector View Post
    And here I thought this is where the thread was going.......

    1305573409-lmhm_btwd2011_6.jpg
    I'll leave that test to the more adventurous, or confused as the case may be.

  15. #15
    Senior Member awfulwaffle's Avatar
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    This might be the most ridiculously awesome thing I've seen on BF.

  16. #16
    Senior Member datlas's Avatar
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    :wave:
    Quote Originally Posted by RUOkie View Post
    never underestimate the idiocy of BF.

  17. #17
    Stand and Deliver FLvector's Avatar
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  18. #18
    Senior Member surgeonstone's Avatar
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    Quote Originally Posted by wphamilton View Post
    It comes up with such frequency, and is debated with so much passion, that it may be one of the most important questions in the sport of cycling, yet no one has really examined it scientifically. Until now.

    The roadie in full regalia, his steely gaze is focused and intent, you give a wave and you're ignored. What's up with that? Would it really hurt him to wave? That's usually a rhetorical question but I set out to find an answer. What does it cost him to wave?

    So I took my road bike to a local hill to perform some coast-down tests while simulating a roadie in training. I selected a hill with a relatively gentle grade so that speeds would be similar. In half the tests I coasted in a regular roadie position, and in half I waved all the way down while trying to maintain the same position. I wanted to make the simulation as real as possible so I wore an actual jersey, tight, and spandex cycling shorts. Helmet, sunglasses. All tests were with hands on the hoods (since careful observation has indicated that training roadies ride on the hoods, or with the same back angle while in the drops).

    This is the test rig: bike.jpg bike.jpgalthough it's Fredded up it is, as you can see, a road bike with standard road bike geometry, normal saddle to bar drop, 700x25c tires.

    To complete the simulation I strapped on a HR monitor and also turned on Strava, as if I were doing hill repeats. For you doubters out there Bike Ride Profile | Coast-down test repeats near Alpharetta | Times and Records | Strava although I didn't use Strava data since my flight recorder box is more accurate. I did three tests coasting, three waving, with no pedaling at any time. Except uphill of course. I started each test at precisely the same point in the road, with the magnet positioned 1/8th of a wheel behind the sensor.

    I threw the second waving run out because passing traffic distorted the data. The final repeat in Strava was not a test run - I just did it because just coasting is pretty boring. Here is the result:
    roadie_vs_waving.jpg
    The vertical axis is miles per hour, the horizontal is units traveled (unit representing approximately 7 feet, one wheel revolution)

    It's pretty clear that waving costs a significant amount of speed, presumably by adding drag. If we need a number, how much drag, here is a real general estimate. Assuming that the highest speed is the terminal velocity for that grade and object (I haven't proven that, but I've been up and down that hill a lot and it is or is close to) then the drag force is equal to the force of gravity. The force of gravity is the same for both roadie and waving, and therefore the ratio of CdxA (Coefficient of drag times area) is the inverse ratio of squared velocities. From the basic drag equation.

    In this case, that comes to about 12% greater drag created by waving. So there you have it: drag is increased by 12% when he waves.
    I'm sensing a Nobel prize in physics.

  19. #19
    Mostly Harmless rjones28's Avatar
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    Quote Originally Posted by truckstop View Post
    getting banned from trollheim. does that mean you win?

  20. #20
    Senior Member
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    Quote Originally Posted by surgeonstone View Post
    I'm sensing a Nobel prize in physics.

    I'm sensing someone who really needs to be given something meaningful to do.

    j.

  21. #21
    Senior Member GuitarBob's Avatar
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    I love it, replicates even. Nice work!

  22. #22
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    26 mph and you call that a hill?

  23. #23
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    Please repeat the tests with various forms of waving, slightly lifting fingers from the bar, maybe a head nod. Really any form of acknowledging that the other cyclist exists.

    I think you also need to consider the amount of power and motivation lost by being denied the satisfaction of a wave or acknowledgement in return. I'm sure everyone dwells on how many cyclists ignored them for the next x kilometers of their ride and that affects performance.

  24. #24
    rugged individualist wphamilton's Avatar
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    Quote Originally Posted by evrythngsgngrn View Post
    Please repeat the tests with various forms of waving, slightly lifting fingers from the bar, maybe a head nod. Really any form of acknowledging that the other cyclist exists.

    I think you also need to consider the amount of power and motivation lost by being denied the satisfaction of a wave or acknowledgement in return. I'm sure everyone dwells on how many cyclists ignored them for the next x kilometers of their ride and that affects performance.
    This was a full arm wave, involving each degree of freedom of motion and to the fullest extent possible. I'm not planning on breaking it down more than that. You can take over with those tests if you wish but I suspect that the results would have limited utility.

    Regarding the subjective effect on ride quality I can tell you this. With an exuberant arm wave it is difficult to refrain from lifting your torso, and when you do manage to keep your shoulders fixed relative to the bike, control is negatively impacted.

    Studies of psychological impact are best left to the pseudo-scientific methods of the practitioners of the soft sciences, and alas, are beyond the scope of my inquiries.

    edit: I may actually repeat with the head nod, because I expect that it actually would result in some measurable increase in drag, which I think would be surprising to almost everyone.
    Last edited by wphamilton; 06-28-14 at 08:31 PM.

  25. #25
    rugged individualist wphamilton's Avatar
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    Quote Originally Posted by MikeWMass View Post
    26 mph and you call that a hill?
    I selected a gentle grade to simulate the realistic speeds of a roadie in training.

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