1. The problem statement, all variables and given/known data hi! first off, thanks for viewing this. I wasn't sure if this would be the right place to post for help, but it's for an engineering challenge so I didn't know where else to go. Also, I'm really sorry if this is a repeat thread, I don't really have time to read through them, and am actually going to be doing some trials on what i already have while I wait for responses. Basically, I have to build a self propelled car that can go up a ramp (which I need to build as well) and travel 1.0 meters horizontally in the air. The height the car gets isn't measured. Coinstraints: -The entire propultion mechanism must be on the car. So I can't use my slingshot-on-a-ramp idea D: -The method of propultion cannot use electricity, explosions, or chemical reactions. I can't afford to buy a bunch of CO2 to use in testing, so I suppose that's out as well. :S -The car must weigh between 0.1 kg to 2.0 kg. -The car can be bought but the method of propulsion and ramp must both be made from parts I assemble. -The ramp can only be a max. of 1.0 meters in length, but there are no height restrictions. 2. Relevant equations I don't even know... :P 3. The attempt at a solution At the moment I have a chassis made out of K'nex and am using a balloon as an elastic to turn the axle after winding it up the other way. The wheels are the biggest I can use without using massive gears and have rubber bands on the outside for traction. I was also playing around with a balloon for air pressure, but it doesn't really create enough force to move the car at all.