Physics Car

Ski_ThEast

Ski_ThEast

Active member
For physics we have a project to make a car, made out of anything but leggos k'nex. The only way to power the car is from a rubber band.

I already have a few ideas in mind, and I've decided I'm gonna use records for the wheels, but if anyone on here has done this before or likes this kind of stuff, let me know of any designs you have.

The goal is to go at least 15m but I'm hoping to go much further than that.
 
1. Shoebox

2. Something to weight said shoebox a bit

3. Axles

4. Wheels

5. Rubberband

Find a way to wrap the rubberband around the rear axle and anchor it to the front of the "car," essentially creating one of those toy cars where you pull it back and it zooms forward. The bigger the rubberband, the more drive you'll have.
 
I built one with a basic frame made out of some wood. It was basically in the shape of an 8. then two pieces of doweling for the axle, and wooden wheels with elastic bands stretched around for grip. Then put a small nail through the back axle for the elastic band to attach to. My thing made it all the way across the gym and had plenty of momentum when it hit the wall.
 
Google image search rubber band cars. There's some nifty ideas there. Looks like one style uses the rubber band to power a propeller and another one uses a system of "gears" to increase the effectiveness of the band.
 
He has the right idea, you want lightweight but weight at the same time. Weight in motion = harder to stop
 
For the car itself make sure the body is light weight with little to no resistance on the wheels and axles.

That being said center whatever weight you put in the car, let it ride the center line between the axles favoring the front axle slightly more.
 
don't use record for wheels, there is almost no surface area and the coefficient of friction is way to low. If you sandwiched like 4-6+ on each side and then put a rubber band around each (like a tire), that would be do able and should work decently. I saw 15m is the goal, but do you simply want to go for distance, or is speed a factor? You can optimize it for either or potentially both with your gear ratio. Also, I assume you are allowed to wind it up, but does it need to have some sort of catch so that it could stay in a loaded position and be triggered by something other than you letting go?

I haven't made a car with rubber bands, but last year I took a class on manufacturing and design and we designed and machined cars to race. They were all built out of metal though and used electric motors, had braking systems etc.
 
How does this really relate to physics? What is it coveting are you learning about potential elastic energy 1/2kx^2.
 
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^ nope.

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2 larger wheels in back-

-Attached to single floating axle (think a straw mounted to frame with a axle going through that).

-Small amount of surface area, but with traction (rubberband around edge of a cd)

-stud attached to center of axle for rubber band

1 smaller, "frictionless" wheel in front-

-also a floating axle

-Use something really light weight for this, theres no reason you need to lose any energy on a front wheel. (But if really light you may need to add counter balance to the front)

Light weight A frame-

-The 2 big wheels mounted on the bottom, the one smaller one on top of the A

-Rubber band mounted in center strut of A frame.

Crank that bitch back and let it go, calibrate it till it works well enough. Make sure the rubber band is not staying hooked on the back axle after the elasticity is exerted, otherwise you'll lose precious coasting distance.

Back when I was a bright little academic, one of the events I competed in Science Olympiad was making a basic car powered by rubber band that traveled an exact distance, it was judged by proximity and time of travel. I rocked the shit out of that.
 
came in here to post something similar... I'll just add one thing. For even less friction on the axles, rub pencil lead over the contact points.
 
make sure your rubber band falls off the axle when it's all done pulling.

you know what i'm sayin. it was awesome watching a few kids' cars stop at 10 feet cause their axle was rewrapping the rubber band

dumb boy scouts

they don't know
 
in 8th grade i made a car out of straws, tape, index cards, paper clips, and a single rubber band, it went 12 meters I think. I used a fan to power it, the biggest issue was having paper wheels that kept folding. if you threw some big records on there for wheels, should do 15M no problem
 
i made one out of a 20 oz bottle. The one issue I could see with using records for wheels is little to no traction. you don't want to lose all of your power with your wheels just spinning and not going anywhere.
 
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