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Mr Buckshot
February 21st, 2008, 02:20 AM
The final challenge of the physics contest this year:

Build a car out of elastic bands and wood. It must run 5.0 m in a straight line, then make a legal right turn and park (at an unspecified distance from the turning point). No electronics or combusting devices allowed. Car must stay intact the whole way, so no self-destructing cars that propel one piece to the right.

Or:

Build a car (not an RC car as I previously thought) that can run into a small artificial pond, drive across the bottom, and come out again. No electronics/combustion again. Can use waterproof materials and buoyancy devices.

I decided to go with the first challenge. Any ideas?

I'll post my design in a couple hours, but here's my first rough idea:

Put two axles perpendicular to each other, one propeller on each axle. Set up the elastic bands in such a way that one propeller will keep turning until the 5 metres is travelled, at which point the second propeller will start turning to shift the car to the right. Basically, this means that I wind up one propeller, and as it unwinds itself it automatically begins winding the second propeller, which then unwinds after 5 metres.

What do you guys think? Help is appreciated. Last year, my team got the gold medals (submarine challenge) and we'd like to get them again.

legionaire45
February 21st, 2008, 02:56 AM
Something a friend of mine got away with due to a technicality on our 9th grade boat project was using a leafblower against a huge (compared to everyone else's) 2 x 2 footish Sail xD.

I've always had some way of computer controlling a project like this (whether it's a physical PC or a robotic system) , but your idea sounds like it might work well.

Phopojijo
February 21st, 2008, 03:51 PM
You could always have a wind-up rubber band pull on a spring-loaded cutter-pin that's designed to let go at X newtons of force. Once the cutter pin snaps by an elastic getting wound around the rear axle getting too stretched -- the spring can push the front axle to turn the wheels right which forced the car to -- well -- turn right.