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  • Bicycle pedal torque applied by foot

    Discussion in 'The main mechanical design forum' started by ahad_yekta2004, Mar 16, 2010.

    1. ahad_yekta2004

      ahad_yekta2004 New Member

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      how much is the torque that a usual person enter over the bicycle pedal ? ( the range )
      i want to know . is it enough to ride a bicycle through drastic uphill bye foot power? or use some booster to drive better . i want to design a hydraulic transmition for bicycle . do i have to use pressure booster to increase the force on rear wheel or the 1:1 transmited turk is enough ?
       
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    3. deltabarn

      deltabarn New Member

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      Action and reaction my friend. If a person does not turn the pedal then he will stand on it and so the maximum torque will = (body mass of the rider x g) x the length of the pedal lever. Remember to consider the gearing of the bike though.
       
    4. ahad_yekta2004

      ahad_yekta2004 New Member

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      tanx for your reply .
      but i didnt mean the max of force . what is the average force over pedal when rider is sitting on bicycle seat . i should consider the usual condition .
       
    5. ConnectUTS

      ConnectUTS Active Member

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      According to http://www.green-trust.org/2000/humanpower.htm "The average, fit, adult rider can produce only 75 watts or 1/10hp when cycling at a continuous 12mph (19.3kph)." This usually happens with a pedaling speed of 60-80 rpm though many rider pedal faster. When I cycle, I usually spin at between 100-120 rpm, but I have been riding for years and have found that the higher speed works better for me.

      To determine what type of mechanical advantage you will need to build into the system need to know the speed you want to travel and the diameter of the wheel [http://www.sheldonbrown.com/rim-sizing.html]. For this discussion we will use approximately 1/2 the speed listed above or 10kph and a wheel diameter of 700C which translates to 1.954 meters in circumference.

      To travel at 10kph the bicycle tire will be spinning at at approximately 86 RPM. As a result if 75 watts is enough then a 1 to 1 gear ratio should work.

      I will let you do the rest of the calculations.
       
    6. jawnn

      jawnn Well-Known Member

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      I remember an old bike magazine article that seemed to prove that most people did not press on the pedals as much as they thought they did. I don’t know how they measured the pressure, but I can see how it would be close to un-measurable, turning so fast.

      Is it really possible to improve the bicycle? My hill climbing is done with very low gears. I also think that this entire obsession with speed is a disease. I would really like to see some slow technology.
       
      Last edited: Jan 30, 2012
    7. jawnn

      jawnn Well-Known Member

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      Have you considered compressed air? I need some sort of light weight power system for a velomobile. I Worked up an electrical system but it was going to need one hundred lbs of batterers.
       
    8. Dana

      Dana Well-Known Member

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      A hydraulic transmission is a very inefficient way to transmit power; you'd be making the rider work a lot harder than he would have to with conventional gearing. Hydraulic (usually called hydrostatic drives) have their place when fine control at low speed is required, but a bicycle drive isn't one of those places.
       
    9. jawnn

      jawnn Well-Known Member

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    10. john12

      john12 Well-Known Member EngineeringClicks Expert

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      It's possible to exert more force than your body-weight though, by actively pedalling and bracing against the handlebars.
       
    11. GoodCat

      GoodCat Well-Known Member EngineeringClicks Expert

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      «How much is the torque that a usual person enter over the bicycle pedal ? ( the range )»
      When riding a bicycle, the pressure on the pedal is limited to the body weight of a person, if a person sits on a saddle then he constantly has 3 points of support and therefore the torque that he can create is approximately equal to 1/3 of his body weight multiplied by the length of the pedal connecting rod, the maximum moment that a person can create by transferring its center of mass as close as possible to the vertical axis of the pedal will be about 1/2 of its mass multiplied by the length of the pedal connecting rod, further simple mathematics.
      «want to design a hydraulic transmition for bicycle»
      Transmission without an additional motor will not allow to go faster. Moreover, the mechanical losses in any gearbox will be greater than the losses in the chain transmission.
      If you want to develop a gearbox for the bike to get away from the need for cleaning and lubrication of the chain and asterisks, you will lose about 5-10% of the torque at a constant rotation speed. If you want to achieve an increase in the speed characteristics of a bicycle in this way, then this will not work (you cannot deceive the laws of physics). The most effective is the direct rotational speed of 95-98%, then there is a transfer with a belt and a chain of about 88-92%, the variator is close in efficiency to chains and belts, the gearbox has the lowest efficiency from 75-85% depending on the type of mechanism, bearings, quantity steps, general mechanical arrangement and oil viscosity.
      «do i have to use pressure booster to increase the force on rear wheel or the 1:1 transmited turk is enough ?»
      The gain effect without loss of rotational speed will be achieved only if you use, for example, an electric motor for a hydraulic amplifier in addition to a person’s muscular strength, otherwise you will only get a decrease in torque or speed, since you will get additional mechanical and hydraulic losses, and rotation source will have constant characteristics.
      In fact, the most effective design is a bicycle with one wheel, the diameter of the wheel and the length of the pedal stem are chosen correctly. Such a bike has a maximum efficiency of about 98%, and also a person gives a maximum torque of about ½ of its mass multiplied by the connecting rod pedal. You just need to learn how to manage it well =)
       

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