Technical Report for Mousetrap Vehicle

EDITOR'S NOTE: For a change, the comments are being left ON. I welcome and would appreciate your thoughts -- this technical report has not been scored yet, so it will be interesting for your feedback to compare & contrast with the judges. Just keep it (pardon the pun) constructive! :D

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Abstract
My team consisted of 4 freshmen in high school, we were all friends and we decided to work as a team to complete a mousetrap vehicle. The mousetrap vehicle in question is a triangular, four wheeled, balsa wood vehicle. It uses the potential energy stored in the spring of the mousetrap car to move. A string attached to the rear axle of the vehicle is also connected to the end of the straightened arm of the mousetrap. When you pull the arm back and wind the string around the axle it creates tension and potential energy. When the arm is released this energy is transformed into kinetic energy and thus the vehicle moves. This report is about how we accomplished this feat.

Introduction
This is our technical report for the MTV’s or the mousetrap vehicles. The mousetrap vehicle is a machine that runs on wheels across the ground. Its power source is the mousetrap located, most often, in its center. The arm is tightened back and the tension in the spring is used to propel the vehicle forward. This project is a branch of SECME a math based club for students at school from elementary to high school. SECME is an acronym for Science, Engineering, Communication, Mathematics, and Enrichment. This basically means that in SECME you must use all of these categories. You use Science to figure out how far the vehicle will go, Engineering to build the best mousetrap vehicle possible, Communication to effectively tell you team mates how something could be improved, Math is used to formulate what the possible outcomes are and if the outcome is grim how to change it, and Enrichment is the bettering of your skills through SECME.
Our focus in this the mousetrap vehicle competition was the build on last year’s success of coming in third place by continuing to use gears, but making a more compact car. The design of our mousetrap actually presented quite a challenge for our build team.
The first thing that my team did was sit down in a group and brainstorm. We thought up several designs and chose the one we thought would perform best.
Then we gathered materials and started to work. There were two people on the design team and two on the build team. The design team was to draw the schematics and write the technical report, while the build team was responsible for the completion of the mousetrap vehicle based on the drawn blueprints. There were times when an unexpected problem would cause us all to focus on only one area but other than that our method simplified the whole process. It kept our priorities straight and helped us to complete the vehicle.
Design
Our design consists of a base with two pieces of balsa wood two axles and four wheels for which we used CD’s. The rear axle is wooden and has the smallest sized gear attached to it. While the front wheel has a metal axle to prevent problems. There is an extra piece of balsa wood attached between the balsa wood, just in front of the front axle. This is for support because the mousetrap is glued to the balsa wood at a 35 degrees. There are then two pieces of balsa wood on each side of the mouse trap glued to the frame of the vehicle. The pieces of wood extend to the end of the frame and contain another axle with a large gear attached. This gear is where the string will go. Then extending from the frame to the top of the tier are two thin support beams. This is to prevent any unwanted movement or misalignment.

Construction Procedure
1. We took two pieces of balsa wood and drilled two holes of 0.6 cm in each, 2.5 cm from the end. We then cut a 5 cm piece of balsa wood and glued it to the very front of the two pieces of the balsa wood so we got a basic “u” shape.
2. We removed all the unneeded parts of the 9.8 cm mousetrap and straightened the arm to 12 cm. We then glued the pieces of balsa wood on to each side of the mouse trap, and drilled identical holes at the end.
3. We then glued the mouse trap to the front balsa wood in the middle of the base and angled it at approximately 35 degrees.
4. The wheels were made by adding rubber stoppers in the center of the standard 11.9 cm in diameter CD’s and by hot gluing a smaller set of wheels to the CD’s to increase their surface area.
5. We ran a metal axle through the front of the mousetrap vehicle near the front of the mousetrap and attached the wheels with the rubber stoppers. The wooden axle of 0.1 cm in width had the smallest gear glued onto it and was fed through the back. This driver gear had 64 teeth. Another gear was on the rear axle. This follower gear had 24 teeth
6. We then put the modified wheels onto the wooden axle. Another thinner piece of wood had the larger gear glued to it. Then that axle was fed into the upper holes.
7. A 30 cm length of monofilament line was tied to the end of the arm and glued to the upper axle.
8. The gears were aligned so that they would properly mesh, and the we glued support beams between the ends of the upper frame and lower frame to provide extra support and take off the stress on the gears.
9. Then we wound up the string, lubricated the axels with graphite powder and watched the science go to work.

Operation of the Mousetrap Vehicle
Our mousetrap vehicle operates by the conservation of potential energy and momentum. We wind the string around the axle and pull the lever arm back. The potential energy is transformed into kinetic energy when released and the axle spins. This causes the gears to mesh and the lower axle spins. The axle spins the wheels and the vehicle moves forward. The efficiency of the vehicle is ratio of the force input to force output. For example, the lever arm to the force output. is equal to the amount of force it takes to pull the lever to the horizontal position, and the output force is the total amount of force used by the car. This input force is equal to the spring constant of the mousetrap multiplied by the distance the lever arm travels (pi times the radius). The output force is equal to the mass of the car multiplied by its measured acceleration (which is Newton’s second law, Fnet = ma). The average acceleration (a) of our car can be calculated by measuring the distance the car travels and the time it takes to cover this distance. Likewise, the efficiency of the driver gear to the follower gear can be measured. Kinetic energy from converted stored potential energy in the spring does the work of making the gears rotate (for every one rotation of the driver gear, the follower gear spins 2 and 2/3rds times), causing the vehicle to move forward. This transfers the rotational motion into linear motion. According to Newton’s 1st law of motion, an object in motion stays in motion in a straight line without accelerating until acted on by an outside force. The outside force that stops the mousetrap car is friction from the floor, causing it to de-accelerate. However, even after the arm of the trap is completely sprung, the vehicle can still coast forward on its momentum (mass multiplied by velocity p=mv).
Since distance equals one-half the acceleration multiplied by time squared, acceleration equals twice the distance divided the time squared. The acceleration and mass are then put in Newton’s second law formula (F = ma). The potential energy of the car is conserved and equal to work done, where potential energy equals one-half the spring constant times the pi radians squared (PE = ½k(πr)^2) and work equals force times distance (W=Fd).

Conclusion/Recommendations
The mousetrap vehicle performed very well considering the amount of trouble we had in building it. The system we used was a slow-release system which is when the gears cause the vehicle to move slowly but the spring unwinds slowly. This causes you to get a greater distance with the limited energy. This is because the energy is stretched out to accomplish greater distance not to gather a greater speed. The completion of our vehicle was only possible through a basic understanding of simple machines, how they work and how they are used. Our design was based on a minimal mass idea in order to have more energy in moving a small mass forward not a large mass over a shorter distance.