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  • Pedal Powered Generator?

    Discussion in 'The main mechanical design forum' started by jawnn, Jan 26, 2012.

    1. jawnn

      jawnn Well-Known Member

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      I am thinking that anyone can build a better pedal powered generator than the ones sold on the internet.
      So I did some math but do not know anything about motor-generators. Like can I get one that will generate enough power at the speed I can pedal, and how much resistance is there? And I was thinking there must be a brushless motor that would work.

      I need only generate enough to recharge a few small batteries, because I use LED lights and charge AA batteries of the 12v batteries.
      I am not a performance cyclist, just a commuter, so I may have a hard time at even 70 rpm.
      The drive wheel will be a cement filled fly wheel.
      70rpm crank cadence x (60/11 sprocket ratio) x [(622mm rim/25.4) / 3†pulley on the motor]= 2701.12 rpm motor speed.
      Has anyone successfully made one of these?

      I am not able to commute (by bicycle) to the internet connection every day ,so please be patient
       
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    3. Ramana Rao

      Ramana Rao Well-Known Member

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      I know of a similar one made here in Hyderabad, India. A generator of 20W was coupled to an epicyclic gearbox of ratio 1:80. It worked quite well as the required input rpm is only 20. The generator specification called for 1800rpm. However a electronic voltage regulator was installed after the generator to control the voltage.
       
    4. jawnn

      jawnn Well-Known Member

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      Can any one tell me the momentum that I would need to run past the resistance of a motor?

      what?
       
    5. Dana

      Dana Well-Known Member

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      Perhaps you could rephrase the question? It doesn't make sense.
       
    6. Gregory L Thompson

      Gregory L Thompson Member

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      Question why do you want a pedal type generator if you design a an electric motor powered by battery to drive generator splitting amperage to supply battery that runs electric motor maintaing battery amps, and sending unused amps to what ever you are running this would become a self contained system, now are you dealing in DC volts or AC volts this can be changed through diode trio, and rectifier the generator can be 12/24/36/48 volts and alot of variables in amperage now if you are needing 12 volts but generator is producing 24 or 36 & 48 utilize a series parallel swictch
       
    7. bnmorgan

      bnmorgan New Member

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      I hope i am misunderstanding that, but it sounds like you are suggesting a perpetual motion machine. Motor running generator generating power to run the motor?

       
    8. jawnn

      jawnn Well-Known Member

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      I need 12 volt dc to charge the batteries? I am thinking that 3000 rpm is the peak efficiency point, but beyond that I have no clue.

      well I use 12volt dc from three 8 amp hour batterers. Our solar cells do not produce enough electricity in the dark of winter. Actually I have no idea what I need.

      I do not want to use a gasoline generator. And it looks like it will be a real good work out to use a bicycle generator, but it is appropriate technology.

      Obviously I will not be using the lights while pedaling. My land lord knows something about charging batterys, but can't tell me if the thing will actually generate enough power to be worth building, because he has no idea how hard it will be to pedal it.

      I think all I need to know is how much resistance will I get back from the generator motor, some of the magnets are very strong.

      I am eliminating as much friction as possible, a belt from the rim pulley to the motor.
       
      Last edited: Feb 1, 2012
    9. cwarner7_11

      cwarner7_11 Well-Known Member

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      Here is a reasonable article on the amount of energy one can expect to generate with a bicycle generator. Note that it focuses on super-athletes, who can peak in the 400-500 Watt range, and generally average 250 Watts. The current world record holder appears to be capable of sustaining an average of 430 Watts of output for an hour.

      I suspect my own capabilities would be considerably less than this.

      To "generate enough to recharge a few batteries" is pretty vague.

      What do you hope to achieve with the cement-filled fly wheel? It will take more energy to get it turning than you will be able to extract with your charger. You would most likely be much more efficient with a direct drive geared to change your desired working rpm to that required by whatever generator you are considering.
       
    10. jawnn

      jawnn Well-Known Member

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      I was reading about how a fly wheel will take out the elliptical non-continuous force in a bicycle crank.

      It looks like I will just have to build the thing and then wish I had not wasted so much time. At least it will give me much needed exercise.

      Actually we have a generator motor that has an out put of 120v dc at 4800 rpm even if I can do only half that....
       
    11. jawnn

      jawnn Well-Known Member

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      No perpetual motion machines for me. Maybe a Zero Point Energy machine would be nice.
       

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