Hey guys, hope this is in the right place first off, but anyway, for one of our engineering projects we are required to design a "rover" that can transport a maximum of 40 pounds (the increments in weight increases by 10lbs per run starting at 10lbs and ending at 40) a minimum distance of ~20 feet. The constraints are that it can use no electric power of any form or any type of fuel, compressed gas, combustion, etc. It must also fit a profile of 2'x2'x3' and the total cost cannot exceed 80$. The solution I have in mind currently is that I would simply take the concept of how one of those rubber band cars work and try to apply it in a scaled up version. Essentially I was looking at 300lb resistance bands that are wrapped around an axle to create tension in the band and when the tension is released the axle rotates thus causing the wheels to move. The main problem I am facing currently with this design is firstly, to withstand a perpendicular force of 300lbs I would need a very thick axle which would have a high circumference and so I would need more elasticity in the bands to be able to wrap around the axle enough times to cause enough rotations of the wheels to travel the distance that I need. Would my concept work in practice? Or is there a better way to go about this that I am not thinking of? I appreciate any and all help that can be provided. Thanks guys!