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What's the best way to put kinetic energy in batteries? Answered

I had the idea to have the kids at my favorite summer camp group to "pump" their own electricity because one of the more primitive camps in that group already pumps their own water, but doesn't use electricity.

What's the best way to put kinetic energy in batteries? When i say best i mean highest mechanical advantage.  

The ways i can think of are:
-shaking a magnet through a coil of wires
-spinning a wheel to shake  "          "
-pedaling to spin the wheel to "       ''
-using a lawn mower sort of wheel.

Also to refresh my memory what are the other ways (with a higher mechanical advantage) to move a magnet with coils to generate electricity?

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KitemanBest Answer (author)2010-04-18

A generator geared to the axle of a large horizontal wheel, maybe a roundabout, maybe a pirate-style capstan, would encourage kids to do it because it would be both a group and a play activity.


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Houdinipeter (author)Kiteman2010-04-18

 Would having it be really wheel be more efficient than a really light one? 
And yeah the competition idea is legit. A game that's available to play all the time (like basketball) might get more than the chore.

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Kiteman (author)Houdinipeter2010-04-18

Not more efficient, as such, but it would gather momentum and keep spinning for a while when the kids stop pushing for a moment.

It would feel easier.

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steveastrouk (author)Kiteman2010-04-18

You could increase the efficiency with big whips too. Made of paracord, for another craft activity. Bad whipmakers push the wheel, good whipmakers test them out on the bad ones. Oh the synergies. ......

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You'll want a big drum to keep time. Maybe making one out of a big blue water barrel could be another project. Shirkers have to wait inside the barrel for their turn to push the wheel.

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Grathio (author)2010-04-18

I don't know the "best" way, but of the ones you listed a circular motion is better than shaking.  In shaking you put a lot of energy into simply turning the magnet around, which doesn't generate any electricity.  When you use a circular motion you don't have that problem.  Once you get it up to speed you only have to put enough energy into it to keep it going.

Many hand-crank generators use gears to increase the advantage, so you can turn it slow but the gears spin the rotor very fast.  Whether this is the best solution depends on a lot of stuff, especially the size of your generator.

There are a number of affordable emergency radio/flashlight things on the market that can generate power by turning a crank.  (Here's one.  Here's another. And a third.)  These also charge cell phones, so it wouldn't take huge hack to power something else.

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Houdinipeter (author)Grathio2010-04-18

 do you think it'd be possible to put these on a way larger scale? How inefficient are these?

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Grathio (author)Houdinipeter2010-04-19

The concept can be scaled up very easily.  Simply use a bicycle for the crank and gears and connect an electric motor or alternator to generate electricity.  Google "Bicycle Generator".

As for efficiency, do you really care?   A single person can generate enough power to run a TV with a bicycle generator so you can easily get useful amount of current out of it.  Overall efficiency of the device is awful since you need to  grow, harvest, and prepare food, digest it and turn it into muscle which turns gears to spin magnets.  It would be vastly more efficient to burn the original food to make steam to turn a turbine.

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Houdinipeter (author)Grathio2010-04-19

 well seeing as we already feed the kids, and have to, it'd probably not be best to just burn the food.
and i mean scaled up to a huge crank the size of a table. (see kiteman's post)

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lemonie (author)2010-04-18

Recumbent bicycle set-up driving a generator.

L

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Houdinipeter (author)lemonie2010-04-18

 how much electricity do these generate compared to solar and wind power?

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lemonie (author)Houdinipeter2010-04-18
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steveastrouk (author)2010-04-18

I don't think you mean mechanical advantage, I think you mean efficiency.

Use chains and belts to run a car alternator.

Steve

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 i assume car alternators cost alot.
is there a diy way?

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Car alternators would be had from an auto breakers for a few dollars. A new one, sure, 150 USD, but ask nicely at the breakers, or find one on Craig's list or something.

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RavingMadStudios (author)2010-04-18

Mechanical advantage is a function of design (i.e. gear ratios and such) which can be applied to any of the methods you list. Maybe look at having them build a windmill to "        ". Letting the wind do all the work instead of spending hours pedaling is the best mechanical advantage of all.

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 yeah but they main point is that the kids could do it as a chore. 

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I see. You want to do it the hard way on purpose. Some sort of character-building exercise, I assume?

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dark sponge (author)2010-04-18

 If you put a battery on a rocket, it gets LOTS of kinetic energy...

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LucasOchoa (author)2010-04-18

 me and my friend tried the bike generator... but something you need to keep in mind is that you need some sort of voltage generator or transformer because you need a steady current...

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