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Turning simple motion into energy.

  1. Oct 2, 2004 #1
    I'm quite new to anything engineering, so could anyone explain to me or show a link on how something like a turning axel could be made to energy such as electricity? It is possible right? :confused: I have this spinning axel and I would like to somehow get electricity from this motion. If anyone knows more on this please post, and thank you for your time.
     
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  3. Oct 3, 2004 #2

    enigma

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    Look up 'inductance' and 'electric generators'

    Most power is basically produced by turning axles. You burn coal, oil, natural gas, etc. and use the heat to boil water into steam (or just use heat from a nuclear reaction). That steam drives a turbine. The turbine turns a big bank of magnets which induce current into surrounding wires.
     
  4. Oct 4, 2004 #3
    A way to see this in action is to get yourself a little dollar store electric car and take the body off. Remove the battery, then wire a flashlight bulb to the two battery leads to the motor. Then when you push the car, the bulb will light up. The motor acts as a generator to create the power to light the bulb.
     
  5. Oct 4, 2004 #4
    hmmm....
    So what do you guys believe would be the simplest method of having an axel turn to make electricity? Just do the same thing that a minicar motor is doing?
     
  6. Oct 5, 2004 #5

    russ_watters

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    That depends on how much energy you are trying to make. What is the purpose of this?
     
  7. Oct 5, 2004 #6
    I have this little brainstorm in my head that I want to create. I don't want to share a whole lot because it might be something (Im about 90% positive it won't work but I got to try ya know?). anyways, this cardboard with an axel thru the middle is going to need to rotate to create electricity. Around 125 volts. Is 125 volts of AC a lot?
     
  8. Oct 5, 2004 #7

    megashawn

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    well, I know that people can't help if we don't know what you are trying to do.

    However, it seems you might need more understanding in just how electricity is created.

    You said:
    well, first a question. What is making this axle spin? Axles do not just spin on their own.

    To generate electricity, you rotate a magnetic field inside conductors. conductors are basically wire. To convert the spinning motion of your axle to electricity, your best bet would be to couple an electric motor to the output shaft of the axle.

    But you still have to spin the axle. This is where people do things like put impellers on the end, and have a river current turn the axle. This is slow, lower power output but steady.

    You could weld a sprocket on the end of the axle, hook a bicylce up to it and peddle away.

    But your biggest trick to making energy with this axle is coming up with the energy needed to spin the axle to begin with.
     
  9. Oct 5, 2004 #8

    russ_watters

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    Harnessing energy in a spinning shaft is as simple as attaching a generator to it. But without knowing how much energy we're talking about here, we can't tell you if a toy car motor or a household auxuliary generator with the gas engine removed is what you need.

    125 Volts of A/C doesn't tell us much of anything: what amperage (or how much energy) are we talking about? A gas generator of the type you can buy at Home Depot runs at constant RPM, providing a constant 120V - but it doesn't provide any power until you plug something into it! (120V, 0 amps, so 0 watts). When you start adding load, a controller regulates the gas flow to the generator, keeping the RPM constant while the power output increases.

    Virtually all of the electricity in the world is generated in a similar way.
     
  10. Oct 5, 2004 #9

    Cliff_J

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    In addition to what's been said, 125V is a lethal level of voltage and extreme care should be taken.

    If you're trying to power some sort of household item that normally runs off wall voltage, the first step is figuring out your power needs (as is said above).

    How much power? Do you understand how to properly isolate the electricity from the machinery like what double-insulated means? The inclusion of cardboard raises a red flag...

    Cliff
     
  11. Oct 6, 2004 #10
    I apologize for how I am not being very discriptive. I realize it can be very annoying to try to be helping someone and they aren't telling you everything.

    The axel will spend from wind. I guess I could say it's like a windmill. The cardboard has "wings" that catch the air and when the axel turns it creates electricity. I need to make approximately 125 volts, 60 Hz, and 1875W. I don't know if that is a lot of electricity created from a simple turning motion :confused: ?

    So you guys are saying to have a magnet on the end of the axel. Then have wire (made of copper or what? does it matter?) spiraled (is the wire touching the axel?) around the axel.


    Could anyone go more in depth about this. Links would also be appreciated.



    That one made me laugh. :rofl:

    I want to thank everyone for taking the time to help me.
     
  12. Oct 6, 2004 #11

    megashawn

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    As russ mentioned, pretty much all electricity is created by turning motion. In most cases steam is used to spin turbines, which spin a generator.

    Now, you can make a simple dc generator, but building your own AC generator is an entirely different trick. I'm even having a hard time finding an AC generator.

    Here is a motor you could use in a windmill type setup. While the ad doesn't give much info, it starts making power as soon as it turns over. Some motors require a certain rpm before they generate power.

    This is a 24 volt generator, and, can be used to charge car or marine batteries. To get the AC voltage you want, just use an inverter. Now, this is a 12vdc to 120vac inverter, but to save money you can just use any old alternater off a car or truck. I think you can get a generic chevy alternator from autozone for around $30. The inverter will be your biggest expense.

    Now, one problem I'm picking up in your plans is the idea to use cardboard for the impeller. On a small scale project, this would work, but the amount of force to overcome to generate a decent amount of energy would not be attainable by cardboard wings.

    You need something stronger for your windmill blades.

    I would say the first thing you need to accomplish would be the windmill portion of your design. You need to make sure you can get your axle spinning some RPM before you worry about harnessing this spin. Keep in mind with the alternator hooked up, it will require that much more force to spin it over.

    A typical alternator, in use on your car or truck takes anywhere from 3-10 horsepower. Going inbetween, lets say 5 hp. 1 hp =746w. 746x5=3730w of energy to spin the alternater at typical operating RPM.
     
  13. Oct 7, 2004 #12

    russ_watters

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    Megashawn pretty much hit the nail on the head(one caveat, I'd look at car alternators on Ebay or in a junkyard. You can get them pretty cheap.). The big problem here is a cardboard windmill just isn't going to get the job done. HERE is a link to something similar to what you are describing - its a 3.5' diameter windmill that generates 400W for charging sailboat batteries in a 28mph wind. A quick calculation based on area and I'd say at the same aerodynamic efficiency you'll need about an 8' wingspan on this thing.
     
    Last edited: Oct 7, 2004
  14. Oct 7, 2004 #13
    Alright thanks guys. I will start my buildings and see if I can get a decent RPM and then post back to you guys.
     
  15. Oct 7, 2004 #14

    Cliff_J

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    You want 1875W continous power - that's going to be a few hundred dollars for an inverter that can supply that kind of power. If what you're powering has an electric motor, you'll likely need to oversize more (maybe a 4000W or 6000W inverter) to accomodate the in-rush current that occurs during motor startup.

    Anyways, figure 90% efficiency for the inverter (which may be optimistic) and you'd need around 174A at 12V. Depending on the car, most alternators put out between 60-100A. So that's two alternators spinning at 2000-2500RPM to make your power needs.

    You'll want to try to find self-exiciting alternators (that only need to be spun up to around 1200-1500RPM to start generating electricity) or hookup a small battery to energize the coils initially. If you get an old alternator designed with a simple voltage regulator you'll be fine, but many imports use the computer to control the regulation so those won't work well. Old GM alternators are easy to hookup to a small battery and short out the regulator (with a paper clip) to make them run wide-open so they operate similar to a DC generator so you could get more power but at the risk of frying the inverter.

    If you search the net, finding a wind generator above 750W is pretty rare. But some guy built a 50ft diameter 12KW wind generator in the early 1900s to charge the batteries in his mansion so its not like it would be so hard to build one a century later if you source the proper parts.

    Cliff
     
  16. Oct 9, 2004 #15
    I think that weather resistance and weight would be two problems with using cardboard for your windmill. Perhaps sailcloth on an aluminum frame?
     
  17. Oct 12, 2004 #16
    It's not actually out doors. I just used the example of the windmill so you could see a general picture. It's actually in an enclosed frame.


    BTW the 1875W is going to power a hair dryer :rofl: . And Im serious.
     
  18. Nov 19, 2004 #17
    You better get a big windmill with lots of torque and rpm. I got an old car alternator attached to a 10 speed bike that I use to charge the small emergency batteries. I have been cranking as hard as I can and I am worn out and I am getting nowhere.
     
  19. Nov 19, 2004 #18

    brewnog

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    So where are you getting this nice steady stream of moving air to power your device?
     
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