Science Buddies: "Ask an Expert"

Hello,

I am a student and i have been asked to conduct a research and development assignment on elastic band powered cars. As i see it, there are four main ways to put together the car; The propellor car, the slingshot car, the barrel and the 'Pull back' design. I have been looking at these four types of designs, and during my research the sites that i have come across (Either sites like this or sites selling assembly kits for the cars) are either more like assembly procedures or just listing the advantages of the product they're trying to sell. My problem is that i can't come up with any of the advantages and disadvantages of each design. Why one might not run, why, if you were designing one for maximum distance, would a ceratin car be the right choice ect. Is there anybody who can give me a general point in the right direction?

Thankyou in advance.

Hi,
The way you might want to think about this is in the context of energy storage. You are storing energy in the band which is then transfered into mechanical energy moving the car along.

You have one method in stretching the band, another method I have seen is twisting the band and it then unravels itself, ever see those balsa wood airplanes with a propeller?

In an experiment such as this the thing you need to quantify is how much energy you can store in the rubber band. In the stretching model you could use a spring scale to measure the force you are applying while stretching the band, like 5lbs of pull. The twisting model might be quantified with a "torque" wrench of some type.

You'll get the max distance out of the band that you can store and transfer the most energy with. Different properties of the band, different rubbers, hard or soft will store different amounts of energy.

Measure that and you'll have a very good experiment.