Wheeled Vehicle

Basic Description
Wheeled Vehicle is a physics event in which the participants must construct a vehicle powered only by a non-metallic elastic solid device. The Participants must be able to adjust the vehicle to travel a specified distance as chosen by the event supervisor and also be able to predict the time in which the vehicle will reach its defined destination.

Basic Construction Parameters
(2005-2006)

The Vehicle should be designed to travel between 5 and 10 meters ans be built to stay inside a 1.5 meter wide lane. The calibration intervals included: regional: 0.5 meters States: 10cm Nationals: 1cm The vehicle must also be only powered by the energy stored in the elastic solid device and must be triggered by actuating a release mechanism with a pencil dowel etc.

For more detailed rule clarifications see: http://www.soinc.org/events/wheeledveh/index.htm

Designs
many different elastic devices have been used including: 1) rubber bands 2) fishing poles 3) bungee cords

Im sure there are others but these are the ones that are most used.

Another thing to think about is a braking mechanism which is almost always built differently by each team to accommodate their vehicle but for everyone thinking to build a vehicle there are systems that you can easily adapt to your device.(for those of you familiar with scrambler this part should be familiar to you) So before we go about discussing are braking mechanism lets think of what we want to accomplish. 1.) Well in this event you will need accuracy(if you want to do well of course) 2.)Somewhat simple so that theres not a whole lot of room for error(I doubt well have to worry about this to much) 3.)and of course we want it to be a relatively strong and reliable system meaning we want it to stop pretty much on the spot specified and of course do this over and over with little to no error.

So with this laid out we know what we want and we can start designing are mechanism.Like I said there are many different kinds of mechanisms that have been used so obviously there are many other things you can use. Anyway One of the mechanisms Ive seen and used on a vehicle is the threaded rod and nut design. Its been used by many in scrambler and wheeled and is usually very reliable and thats why people use it. the details of how you build it and how you implement it is up to you but the general idea will be discussed. First off you need a threaded rod a nut(preferably a wing nut) and something to hold the nut. So first off we might want to know how many revolutions of the wheel it will take for us to reach 10m. we do this by using the formula for the Circumference of a circle which in this case is our wheel: C=pi*diameter(of the wheel). After figuring that out(in cm) divide 1000 by are Circumference and you will know the amount of revolutions of the wheel you will need to reach our maximum distance 10m. now lets start with looking at a diagram of our braking mechanism. Heres the link: http://server5.pictiger.com/img/354879/picture-hosting/wvbr-1.php

Okay so lets first start by looking at the blue line which in this case is our axle(which is the threaded rod) The red line represents our wing nut the green circles of course represent our wheels and finally the green line is rod that holds our wing nut in place.So as the wheels and axle spins the wingnut( because its held by the green rod in our diagram) will move down towards the chassis between the wheel and the inner assembly.Eventually this nut will hit the chassis and lock up the axle. one thing I forgot to mention was that you might want to put some kind of grip material like sand paper or rubber on wear the nut locks with the chassis so it locks up better.So thats really it for that breaking system very basic but reliable and as accurate as you make it to be. In order to use this system for calibration all you would simply have to do is start the nut on the chassis and then wind it out to the distance you need thinking about how much distance you get per turn of the wheel you can easily figure this out using the formula above. AS you might have figured out theres one minor flaw in doing this. you cant turn the wing nut until you move that green rod in the diagram so make it removable And thats all there is to it. Of course you will have to figure out how to for example get the car moving from the elastic device you used. Which could even be as simple as attaching it to the axle.But this is easily adaptable.

Competition
So now we've got a vehicle(or at least an idea on how to build one and now were ready to compete.As always you need to wear goggles and you may also bring any tools or computing device to assist you in calculating distance/time As always your vehicle must be impounded before competition starts and they will not announce the target distance until the last vehicle is impounded. As said earlier the competition will be in a 1.5 m wide lane and will be on a relatively smooth level corridor. Before you run your vehicle you will be asked to predict your vehicles travel time. You are not allowed to change your prediction for the second run.You will have a total of 10 minutes to run your vehicle. At the judges signal only will you trigger your release mechanism.

Helpful Links
http://www.soinc.org/events/wheeledveh http://www.tx.ncsu.edu/science_olympiad/Event_information/Wheeled_vehicle/wheeled_vehicle.htm