Need help with elastic/ballon vehicle project

[Hyperfluxe]

I need to design a a vehicle using only elastics and/or balloons as a source of energy, and the cost of the overall material must not exceed $20. Now, I am not asking you guys to do the work for me, but I need ideas because there is a catch. The vehicle must do a hairpin turn at a certain point: here is the figure of the path.

The vehicle needs to perform a full 180 degree turn between zone 1 and 2, but I just can't figure out how...any ideas or hints would be appreciated. This might not be the right forum for this, if so please let me know. Cheers.

 

[danielu13]

Are there any other requirements for the other zones? And this would be a land vehicle, correct?

 

[Hyperfluxe]

No other requirements and yes it's a land zone, on a table.

 

[danielu13]

I would try wrapping the elastic around an axle, and find the point at which the car will be at the turning point. At this point in the elastic have a way for the force provided by the elastic switch directions to a steering system, and then back to the original direction. I'm trying to think of how you could do this mechanically, but haven't figured out an easy way to do it yet. I've thought of a system of gears, with which at one period of one of the gears, it would change the direction of the force and then revert to the original direction. This seems like it may be complicated. You could also use an electromagnet and a capacitor that is charged by the motion of the elastic and is triggered when it reached a certain charge, which would be the point of the turn, but that would be even more complicated. Just a couple ideas.