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Is maximum human torque limited by body weight? (cycling)

  1. Oct 28, 2015 #1
    I have tried to get some answers related to a humans ability to produce power and torque on cycling forums with mixed response. So I came to the experts to help me out!

    Basically some cyclist belief that the maximum torque a human can produce is solely limited by their body weight keeping them down or they would just lift up.

    And others believe you can hold on to the handlebars and also counter balance the one leg by pulling on the other, thus maximum torque is not entirely dictated by your weight but rather your ability to counter all the forces.

    Also would maximum torque always occur at zero rpm or would it be possible to achieve it at a higher rpm?
     
  2. jcsd
  3. Oct 28, 2015 #2

    russ_watters

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    Staff: Mentor

    Standing up while pulling up on the handlebars enables a force greater than your weight. It may also be possible to lift up with one foot while pushing down with the other when clipped in.

    The thing is, though, maximizing input torque is generally not an important consideration, since you have bikes with so many gears today. Maximizing or managing (for efficiency/duration) power output is more critical.
     
  4. Oct 28, 2015 #3
    Ok, Thanks for clarifying that. Would max torque always occur at zero rpm? Or if given enough resistance, would the momentum of the cyclist's legs and drive train be able to contribute to a higher torque at higher rpm, say 30-40rpm?
     
  5. Oct 28, 2015 #4
    The amount of torque produced isn't constant. You can generate far more torque with the pedals in a horizontal position than in a vertical position, when your weight won't be any help. If you move at a very low rpm, you probably won't be able to use your speed to get past the pedal position with low torque, and you will get stuck if the minimum amount of torque isn't enough to overcome resistance.
     
  6. Oct 28, 2015 #5
    High performance bicycling uses straps or clip in shoes to allow torque during the upstroke. This also overcomes the problem of lifting up the rider if they push down on the pedal with more force than their weight.
     
  7. Oct 29, 2015 #6
    Lets add some numbers & please entertain me with using a 100kg cyclist, always exciting to see examples which one can relate to :)

    Forgive my maths if it makes no sense. it is after all a collaborations of my understandings of universal physics guided by my assistant, Google.

    If a 100kg cyclist would put all is weight onto one pedal with no weight on his seat or handle bars and the other foot held totally neutral to any force.

    He would be pushing 980.67 Newtons into the pedal. Provided the crank and pedal is at 3 0'Clock on 172.5mm crank arms (standard size) He would be producing 169.16Nm at the crank spindle?

    Now considering this is essentially just a cyclist in a ballet pose on one pedal. Adding the force of the other leg pulling and the arms pulling on the bars to push even more force into the downstroke surely this number could be doubled leaving a human cable of pushing over 300Nm! A respectable number even for sports cars.

    All of this would take place at 0km/h. Would this be the highest point of torque or could it increase even more once the legs are rotating and have momentum behind them?

    I am aware that power = speed and that achieving a higher RPM with even just 90Nm or so would result in higher wattage/speed. Im just curious at which point max torque is being produced.
     
  8. Oct 29, 2015 #7

    russ_watters

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    Staff: Mentor

    The highest torque is at 0 rpm. As you start pedaling, some of the force generated by your muscles goes into making your legs move and therefore doesn't get transmitted to the pedals.
     
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