Mousetrap Vehicle

Mousetrap Vehicle is is a building event in which teams build a vehicle powered by two mousetraps. The vehicle must be capable of traveling down a straight track as quickly as possible, and stopping as close to the finish line as possible. The track is 10.00 m long for Regionals; for State the length will be announced before the competition. The length of the State track will be between 8.00 and 12.00 m in 1.00 m intervals.



How It Works
The mousetrap is mounted on the car. When the mousetrap is triggered, they pull their killbar, which is attached to a string, attached to the axle, attached to wheels. The pulling of the killbar pulls the string. So, if you wind the string around the axle, when the string is pulled, it will spin the axle, turning the wheels, propelling the car.

Building
Building materials you can use vary greatly, depending on your level of skill. Experienced builders may use light balsa in pre-designed arrangements. You could probably find kits available in most hobby stores that can educate you on how a mousetrap vehicle works. The kits will most likely be make of Balsa wood, but some kits are available made of plastic (careful examination should be used to ensure that these kits don't have pre-made mousetraps or illegal methods) made for home experiments. Many ways can be used to build a mousetrap vehicle, but it is suggested that you go to the Mousetrap Vehicle Forum for tips and information.

Number of Turns
To figure out the number of winds needed, all you must do is get the circumference of your wheels that are being driven and divide the distance by circumference. Round up if you don't want a 1000 point penalty! However, due to inertia, testing is HIGHLY RECOMMENDED to find the number of winds. Some vehicles need more or less than others, even with wheels of the same size.

Standard 12 cm CD's need to be wound 19 times to hit 7.16 meters. However, this is MATHEMATICAL and is no substitute for REAL TESTING. When testing however, the mathematical number of winds is useful to use as a starting point.

Making Your Car Go the Distance
If for some reason, your car can't travel the full ten meters (2011), try these tips (note:if your car isn't moving at all, look at the next section, as you most likely need more power).

-Make your drive axle thinner, this will allow you to wind your string around the axle more times, and thus your car will go farther.

-Make your drive wheels larger; wheels with a larger circumference will travel more with each rotation.

-Make your drive string longer (note that this also entails that you make your lever arm longer, and you may also have to increase the distance between the two axles so you don't have string just hanging).

-Make your car lighter

Making Your Car Faster
Alright, so your car can now travel 10 meters. What's next? Make it faster! Follow these tips (note that they are opposite of the distance tips, so you will need to find a balance between the distance you can travel and speed; you will generally want to 'just'be able to make the distance with a little wiggle room).

-Thicken your axle: wrap some tape radially around the axle, you will be surprised as to how much faster this makes your car. This also helps if your car isn't moving at all.

-Use smaller wheels, they need less force to complete a rotation.

-Make your car lighter

Making Your Car Accurate
You've got a speedy car, and now you just have to keep testing 'till your car is accurate! I highly recommend the employment of a braking system, especially a wingnut system. Look up the scrambler braking systems for some ideas. Also, when testing, test with the 16 oz. cup, you will be surprised as to what a difference it can make. If your car is struggling in pushing the cup, look in the speed tip section. (Division C)

Making Your Car Go Straight
Okay, you're almost done! Some years, straightness has been enforced more than others. If you cannot build the axles to be exactly parallel, then there are some other options. One commonly used solution is to build the car in two halves. The front axle will be part of the front half, and the rear axle will be attached to the back half. The two halves of the vehicle are connected together with a bolt that runs to the middle. Here is a modified example of this method. To adjust the path of the vehicle, simply loosen the bolt, turn the front half, and lock it in place by tightening the bolt again. Now you can adjust how straight or arched the path of your vehicle is!

General Tips
CD's or vinyl records are common wheel ideas. Rubber bands can be placed around CD's to add traction. Also, good wheels can be found at a local hobby store. Airplane wheels are often light and come in a variety of sizes. The only problem is they can sometimes be reasonably expensive.

If possible, try to test on a surface similar to the one that you will encounter at the competition. Testing on tile and then competing on hardwood will affect your vehicle's performance. Best way is to test on multiple surfaces, and keep data for each one. Also, the importance of clean floors cannot be emphasized enough. Your results will be varied if the floors are dusty or have small pieces of trash on them.

For string, Kevlar fishing wire works quite well. Sewing thread breaks fairly easily. It is best to have thin string so that the thickness of the string doesn't interfere with winding the string.

When building, it may be best to move the mousetraps as far from the driving wheels as possible. This enables you to maximize the length of the string being wound. It is not practical to use a bar more than 34 cm (in 2010) as that is how large the distance between axles can be. The reason is that if the end of the bar ends up outside the axle (relative to the center of the car), the string must extend back to the axle to wind around it, so any additional string is wasted. Therefore, unless placing your mousetraps outside the non-driving axle, the maximum string length that can actually be would around the driving axle is around 70 cm.

When you wind the string, lock the mousetrap, hold the string tightly (you don't want any slack on the string around the axle), and turn the axle in the opposite direction that you want it to go. If you are using the third method, then you want to wind the trip back first, so you would spin the axle forward, wind around the pin, and spin the axle backward.

Places to practice after cleaning the surfaces may be the, School Gym, Cafeteria, Hallways, or any Local Buildings with smooth flat surfaces.