I already have a specific design in mind. However, I'm not sure what to use as materials for some of the parts. Not allowed to use kits of any sort. Components that need material suggestions: Belt Pulley System -- Two pulleys, one smaller (1-2 inch diameter), and one larger (5-6 inch diameter) Lever Arm -- Light and strong. Wheels -- (1-1.5 foot diameter), low rotational inertia. Also, what type of string is best for attaching to the axle? What size axles are most convenient i.e. ease connecting with other parts, and efficient? What is the strongest mousetrap, or where can I purchase strong helical torsion springs? Attempting to make a vehicle that travels over 250 feet; I need the best possible materials. Any additional relevant information is welcome.