# I'm building a cart

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I'm building a cart which must be powered by TWO elastic bands only, it must ran at least 2 meters, which isn't hard, but my goal is at least 12 meters, which isn't very hard either(the longer the better). I have some ideas of how to power the cart and please help me to choose and give me some more ideas!

(it must be in 3/4 wheels)

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How is this cart being propelled?

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How is this cart being propelled?

The basic "rubber band car" is two axles with wheels on each end, and a rubber band wound around the axle to spin it. You anchor one end of the band to the car, wind up the wheels in reverse, and when you release the car the rubber band spins the axle and wheels and it rolls forward.

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a bit like on those model airplanes to power the prop, but attatched to each wheel instead.

then set down your car, run it backwards to wind up the bands and let go

its not an Original idea/method, but its a known worker

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a bit like on those model airplanes to power the prop' date=' but attatched to each wheel instead.

then set down your car, run it backwards to wind up the bands and let go

its not an Original idea/method, but its a known worker [/quote']

i need some better ideas

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well if the elastic doesnt have to be ON the cart, then why not have a free wheeling one and use something like a catapult system?

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well if the elastic doesnt have to be ON the cart, then why not have a free wheeling one and use something like a catapult system?

maybe, ill try

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I did this once. I made it four-wheel drive (the front axle's band goes to a point on the opposite side of the car than the rear axle's band so it rotates the same way. Use as many elastic bands as you can (all the same length or very close, so you don't have to only partially wind one of the bands). Use the same number on both axles so they don't overpower each other. Then just wind up until you can't anymore without breaking them, and let loose

You might also consider using something to give the wheels 'treads'. This'll increase friction and thus traction, so more of your power will go to use moving the car rather than spinning the tires. Just don't cover the entire wheel, because this could bring you back to square one (depending, of course, on the material)

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I did this once. I made it four-wheel drive (the front axle's band goes to a point on the opposite side of the car than the rear axle's band so it rotates the same way. Use as many elastic bands as you can (all the same length or very close' date=' so you don't have to only partially wind one of the bands). Use the same number on both axles so they don't overpower each other. Then just wind up until you can't anymore without breaking them, and let loose

You might also consider using something to give the wheels 'treads'. This'll increase friction and thus traction, so more of your power will go to use moving the car rather than spinning the tires. Just don't cover the entire wheel, because this could bring you back to square one (depending, of course, on the material)[/quote']

can u draw me like a diagram or something? you can upload your img @ www.imageshack.us

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NOT well done, but I think you'll get the gist. Lines to the circle on bottom diagram = elastic band to a nail. The other axle is on the other side, I forgot this in my post. The elastic band doesn't need to go around, just make sure it'll wind up

The lines on the wheel are elastic bands. That's what I had used to make the 'treads'. Of course, my car needed them because my wheels were only cardboard. With a better choice of wheels you can probably get a lot better traction.

I personally found it better to wind each axle up by hand, but make sure you're turning the wheel the right way. If you're not sure, just roll it backwards a bunch of times.

Also, a note: this will result in a car that is on an angle, because one wheel has to be above the chassis and another below. Just in case you couldn't visualize it (since my drawing doesn't make that clear) I thought I'd tell you.

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NOT well done' date=' but I think you'll get the gist. Lines to the circle on bottom diagram = elastic band to a nail. The other axle is on the other side, I forgot this in my post. The elastic band doesn't need to go around, just make sure it'll wind up

The lines on the wheel are elastic bands. That's what I had used to make the 'treads'. Of course, my car needed them because my wheels were only cardboard. With a better choice of wheels you can probably get a lot better traction.

I personally found it better to wind each axle up by hand, but make sure you're turning the wheel the right way. If you're not sure, just roll it backwards a bunch of times.

Also, a note: this will result in a car that is on an angle, because one wheel has to be above the chassis and another below. Just in case you couldn't visualize it (since my drawing doesn't make that clear) I thought I'd tell you.[/quote']

Thx! I had an idea of 4x, but yours is much better! I wonder how far can this cart run.

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Trebuchet, always use the trebuchet. That'll surprise them all.

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If you fling your cart using a trebuchet, and the trebuchet is powered by two elastic bands, does that count?

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I think it would be detrimental to your grade when the car crashes into the person standing at the 2-meter line.

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But the point is the bands don't need to be in the cart to power it - they're just extra mass you have to move around.

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xtraxxl ,

How is your test working out ?

I use to do this kinda stuff as kid , paper planes were the best .

btw in the cart means - an existing outer shell must exit in order for it to be in-side but I wouldn't count on how you were advised .

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correction : an outer shell must exist **

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