Page 4 of 4 FirstFirst ... 234
Results 76 to 93 of 93
  1. #76
    RoadBikeReview Member
    Reputation: velodog's Avatar
    Join Date
    Sep 2007
    Posts
    5,422
    Quote Originally Posted by tlg View Post
    And.... do you think the energy moving their arms somehow gets returned into the bike as forward motion?
    If so, could I shake may arms to make me go faster?
    Shake your arms all you want, I'm saying that the movement of their arms is a direct result of the bikes bouncing over the cobbles, suspension losses. A visual of the "resulting heat in the frame or the human" that DrSmile deems unlikely.
    Too old to ride plastic

  2. #77
    tlg
    tlg is offline
    RoadBikeReview Member
    Reputation: tlg's Avatar
    Join Date
    May 2011
    Posts
    9,291
    Quote Originally Posted by velodog View Post
    Shake your arms all you want, I'm saying that the movement of their arms is a direct result of the bikes bouncing over the cobbles, suspension losses. A visual of the "resulting heat in the frame or the human" that DrSmile deems unlikely.
    I was agreeing with you, and adding to what you said. Energy transmitted vertically isn't returned.
    Custom Di2 & Garmin/GoPro mounts 2013 SuperSix EVO Hi-MOD Team * 2004 Klein Aura V

  3. #78
    RoadBikeReview Member
    Reputation: velodog's Avatar
    Join Date
    Sep 2007
    Posts
    5,422
    Quote Originally Posted by tlg View Post
    I was agreeing with you, and adding to what you said. Energy transmitted vertically isn't returned.
    Sorry, I misunderstood, I just reread what you wrote, and see that now. Excuse me.
    Too old to ride plastic

  4. #79
    RoadBikeReview Member
    Reputation: Lombard's Avatar
    Join Date
    May 2014
    Posts
    3,854
    Quote Originally Posted by tlg View Post
    You're kinda thinking correctly. But the tire need not leave the ground. If you and the bike deflect upwards 1mm, you don't leave the ground. But it takes significant energy to move 150+lbs up 1mm. Now repeat thousands to tens of thousands of times.
    ........and then think of all the tens of thousands of times that energy was wasted going up and down rather than propelling you forward.
    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein

    "Beware of geeks bearing formulas."
    -- Warren Buffett

    "Education is what you get when you read the fine print. Experience is what you get when you don't. -- Pete Seeger



  5. #80
    RoadBikeReview Member
    Reputation: Lombard's Avatar
    Join Date
    May 2014
    Posts
    3,854
    Quote Originally Posted by Jay Strongbow View Post
    So you saying/thinking rumble strips don't slow down a bike? Go try it.

    Oh yeah, they slow you down alright - especially when hitting them at over 20mph. It stopped her on a dime and she was sent away in an ambulance.
    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein

    "Beware of geeks bearing formulas."
    -- Warren Buffett

    "Education is what you get when you read the fine print. Experience is what you get when you don't. -- Pete Seeger



  6. #81
    Matnlely Dregaend
    Reputation: DrSmile's Avatar
    Join Date
    Jul 2006
    Posts
    4,594
    There are literally gravity batteries that function on this fundamental physics principle. Energy spent moving an object upward against gravity is ALWAYS returned when it comes back down. A bouncing ball loses no energy in it's vertical motion, it loses it only through compression of the ball itself and through aerodynamic loss, plus loss by deformation of the surface it bounces upon.
    “Bicycling has done more to emancipate women than anything else in the world.” - Susan B. Anthony 1896
    "Cycling and ethical bankruptcy have always gone together." - Bike Snob NYC
    "White personifies this generation's obsession with superficiality, one in which a carefully curated social media post is more important than the actual ride" - Daimeon Shanks
    "I haven't %^&* like that since I was an altar boy" Hank Moody

  7. #82
    RoadBikeReview Member
    Reputation: velodog's Avatar
    Join Date
    Sep 2007
    Posts
    5,422
    Quote Originally Posted by DrSmile View Post
    There are literally gravity batteries that function on this fundamental physics principle. Energy spent moving an object upward against gravity is ALWAYS returned when it comes back down. A bouncing ball loses no energy in it's vertical motion, it loses it only through compression of the ball itself and through aerodynamic loss, plus loss by deformation of the surface it bounces upon.
    Granted, the energy is not lost, but it is lost to forward momentum.
    Too old to ride plastic

  8. #83
    tlg
    tlg is offline
    RoadBikeReview Member
    Reputation: tlg's Avatar
    Join Date
    May 2011
    Posts
    9,291
    Quote Originally Posted by DrSmile View Post
    There are literally gravity batteries that function on this fundamental physics principle. Energy spent moving an object upward against gravity is ALWAYS returned when it comes back down. A bouncing ball loses no energy in it's vertical motion, it loses it only through compression of the ball itself and through aerodynamic loss, plus loss by deformation of the surface it bounces upon.
    Well you could build a gravity battery into your bike to recapture the vertical energy. Then use it to power a motor to transfer it to forward motion.
    Custom Di2 & Garmin/GoPro mounts 2013 SuperSix EVO Hi-MOD Team * 2004 Klein Aura V

  9. #84
    Matnlely Dregaend
    Reputation: DrSmile's Avatar
    Join Date
    Jul 2006
    Posts
    4,594
    Quote Originally Posted by velodog View Post
    Granted, the energy is not lost, but it is lost to forward momentum.
    If it converts horizontal energy to vertical energy then I would argue that it must be returned to forward momentum on it's downward return, why would it only work that way on it's way up?
    “Bicycling has done more to emancipate women than anything else in the world.” - Susan B. Anthony 1896
    "Cycling and ethical bankruptcy have always gone together." - Bike Snob NYC
    "White personifies this generation's obsession with superficiality, one in which a carefully curated social media post is more important than the actual ride" - Daimeon Shanks
    "I haven't %^&* like that since I was an altar boy" Hank Moody

  10. #85
    Matnlely Dregaend
    Reputation: DrSmile's Avatar
    Join Date
    Jul 2006
    Posts
    4,594
    Quote Originally Posted by tlg View Post
    Well you could build a gravity battery into your bike to recapture the vertical energy. Then use it to power a motor to transfer it to forward motion.
    Let's patent a bounce battery. The BMX guys would love it.
    “Bicycling has done more to emancipate women than anything else in the world.” - Susan B. Anthony 1896
    "Cycling and ethical bankruptcy have always gone together." - Bike Snob NYC
    "White personifies this generation's obsession with superficiality, one in which a carefully curated social media post is more important than the actual ride" - Daimeon Shanks
    "I haven't %^&* like that since I was an altar boy" Hank Moody

  11. #86
    tlg
    tlg is offline
    RoadBikeReview Member
    Reputation: tlg's Avatar
    Join Date
    May 2011
    Posts
    9,291
    Quote Originally Posted by DrSmile View Post
    If it converts horizontal energy to vertical energy then I would argue that it must be returned to forward momentum on it's downward return, why would it only work that way on it's way up?
    Your argument would be unequivocally wrong.
    The horizontal force is transferred to vertical because of bumps. You'd need perfectly placed bumps to transfer it the other way.

  12. #87
    RoadBikeReview Member
    Reputation:
    Join Date
    Oct 2013
    Posts
    592
    Quote Originally Posted by DrSmile View Post
    If it converts horizontal energy to vertical energy then I would argue that it must be returned to forward momentum on it's downward return, why would it only work that way on it's way up?
    The problem is certainly an interesting one to think about, especially from a physics point of view. But remember we are not dealing with rigid, linear bodies in a zero loss environment.

    From a practical point of view, most would agree, even without trying it - normally riding over a parking lot full of wood 2 X 4s spaced every 2 feet at 10 mph would take a lot more power (watts) than maintaining 10 mph over the same "smooth" distance with no bumps. In a perfect situation with no losses, it would, "in theory" be the same.

    Now let's change the "mind" test slightly - say we space the 2 x 4's every 10 feet, and we do 2 tests
    1) one where cyclist rides normally over the 2 x 4s at 10 mph - measure power
    2) another where he bunny hops expertly over the 2 x 4s at 10 mph, missing them entirely - measure power.
    Again, most cyclists would correctly guess that doing 2) would take less power.
    So why?

  13. #88
    RoadBikeReview Member
    Reputation:
    Join Date
    May 2010
    Posts
    7,114
    Quote Originally Posted by DrSmile View Post
    If it converts horizontal energy to vertical energy then I would argue that it must be returned to forward momentum on it's downward return, why would it only work that way on it's way up?
    Sometimes common sense shouldn't be ignored. But hey if you want to build a case that rough roads are as fast as smooth roads then have at it.

  14. #89
    RoadBikeReview Member
    Reputation:
    Join Date
    Nov 2013
    Posts
    390
    Quote Originally Posted by Z'mer View Post
    The problem is certainly an interesting one to think about, especially from a physics point of view. But remember we are not dealing with rigid, linear bodies in a zero loss environment.

    From a practical point of view, most would agree, even without trying it - normally riding over a parking lot full of wood 2 X 4s spaced every 2 feet at 10 mph would take a lot more power (watts) than maintaining 10 mph over the same "smooth" distance with no bumps. In a perfect situation with no losses, it would, "in theory" be the same.

    Now let's change the "mind" test slightly - say we space the 2 x 4's every 10 feet, and we do 2 tests
    1) one where cyclist rides normally over the 2 x 4s at 10 mph - measure power
    2) another where he bunny hops expertly over the 2 x 4s at 10 mph, missing them entirely - measure power.
    Again, most cyclists would correctly guess that doing 2) would take less power.
    So why?
    Measure the power with what? Bike power meters aren't going to be able to measure the energy/power needed to lift the bike several inches off the ground to clear the 2x4s.

  15. #90
    RoadBikeReview Member
    Reputation:
    Join Date
    Oct 2013
    Posts
    592
    Quote Originally Posted by cooskull View Post
    Measure the power with what? Bike power meters aren't going to be able to measure the energy/power needed to lift the bike several inches off the ground to clear the 2x4s.
    Yep, but for that sake of this test, assume that the power needed to lift the bike is somehow measured, and found to be very low in comparison to the power difference measured by a power meter in both test cases.
    I'm trying to point out that bunny hopping is very much like having a fine tuned suspension that would need to lift only a small weight (say the bike at 18 lbs) to clear bumps versus needing to lift the bike + rider weight (say 190 lbs) to clear them.

  16. #91
    RoadBikeReview Member
    Reputation: velodog's Avatar
    Join Date
    Sep 2007
    Posts
    5,422
    Quote Originally Posted by Z'mer View Post
    Yep, but for that sake of this test, assume that the power needed to lift the bike is somehow measured, and found to be very low in comparison to the power difference measured by a power meter in both test cases.
    I'm trying to point out that bunny hopping is very much like having a fine tuned suspension that would need to lift only a small weight (say the bike at 18 lbs) to clear bumps versus needing to lift the bike + rider weight (say 190 lbs) to clear them.
    Why not find a freshly resurfaced road with rumble strips cut into the shoulder and ride, say two miles, on a bike with a power meter, on the rumble strips for the whole two mile at a constant power. Then go back and ride the same two miles, in the same direction, at the same constant power, except this time riding on the fresh smooth surface beside the rumble strip and see which is traversed at the higher speed.
    Too old to ride plastic

  17. #92
    RoadBikeReview Member
    Reputation:
    Join Date
    Nov 2013
    Posts
    390
    Quote Originally Posted by velodog View Post
    Why not find a freshly resurfaced road with rumble strips cut into the shoulder and ride, say two miles, on a bike with a power meter, on the rumble strips for the whole two mile at a constant power. Then go back and ride the same two miles, in the same direction, at the same constant power, except this time riding on the fresh smooth surface beside the rumble strip and see which is traversed at the higher speed.
    I'd hate to be the guy riding 2 miles of rumble strip... at least if you ever wanted to have children in the future

    Anyways, don't forgot to pump up the 23c tires to 140 PSI for maximum efficiency

  18. #93
    RoadBikeReview Member
    Reputation: Lombard's Avatar
    Join Date
    May 2014
    Posts
    3,854
    Quote Originally Posted by Jay Strongbow View Post
    Sometimes common sense shouldn't be ignored. But hey if you want to build a case that rough roads are as fast as smooth roads then have at it.
    Sometimes common sense isn't so common.
    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein

    "Beware of geeks bearing formulas."
    -- Warren Buffett

    "Education is what you get when you read the fine print. Experience is what you get when you don't. -- Pete Seeger



Page 4 of 4 FirstFirst ... 234

Similar Threads

  1. Velonews publishes tire rolling resistance test results
    By Migen21 in forum Wheels and Tires
    Replies: 30
    Last Post: 10-31-2016, 12:22 PM
  2. Lighter tire or less rolling resistance?
    By bvber in forum Wheels and Tires
    Replies: 30
    Last Post: 05-08-2012, 09:31 PM
  3. My rolling resistance test
    By Scott D in forum Cyclocross
    Replies: 10
    Last Post: 08-20-2011, 07:58 AM
  4. tire rolling resistance
    By PoorCyclist in forum Wheels and Tires
    Replies: 5
    Last Post: 06-02-2011, 05:56 PM
  5. cross tire rolling resistance
    By MIN in PDX in forum Cyclocross
    Replies: 20
    Last Post: 07-08-2008, 12:05 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •