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Mousetrap Car Design

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Lexie Hofmann

on 23 January 2013

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Transcript of Mousetrap Car Design

by Lexie Hofmann Research Research Results Car Design Bill of Materials After the original construction of the car, there were several problems. The vehicle got stuck at the starting line and would only move after a few pushes. Once it started moving, it went about 20 feet, all the while turning sharply left. The back axle also "caught" at certain times, causing the car to lose momentum. To begin my mousetrap car design, I researched building ideas and suggestions for materials, as well as the physics concepts that would allow for the most effective vehicle. •Lighter cars are easier to accelerate; heavy cars coast more, but take more energy to start (less control due to coasting)
•Decrease surface friction (axles and wheels)
•Make the car aerodynamic: less fluid friction (long body, not very wide)
•Increased traction on wheels = more controlled (harder to spin out)
•Longer lever arm = less acceleration, but won’t spin out
•Reasonably long lever arm: have to have enough torque to keep moving
•Reduce weight, reduce axle friction, long lever for best mechanical advantage
•Small diameter axle, large diameter wheels (car goes further with every axle rotation)
•Cover wheels with tape, rubber bands, or cut-up balloons (slipping wheels = energy loss)
•Adding tape to rear axle can reduce slippage of string
•Use glue instead of bolts to attach mousetrap to frame (glue will hold well, bolts add weight) Based on my research, I created three different thumbnail sketches that I would possibly use to design my mousetrap car. Construction and Alterations Mousetrap Vehicle Fall 2012 http://www.mousetrap-cars.com/distance_pics.htm http://www.wikihow.com/Adapt-a-Mousetrap-Car-for-Distance http://www.ehow.com/how_5558896_build-mousetrap-car-distance.html http://www.docfizzix.com/design-help/mouse-trap-car/how-to-plans/kb0003.shtml http://www.ehow.com/how_6449147_step_by_step-build-mouse-trap-car.html http://www.ehow.com/how_6779100_build-mouse-trap-car-distance.html http://www.docfizzix.com/help.htm http://www.mousetrap-cars.com/construction_tips.htm http://www.ehow.com/how_4886932_mousetrap-car-further.html http://www.ehow.com/how_7691924_make-distance-mouse-trap-car.html Inventor Design I combined different aspects of the three sketches to form my initial inventor design, which would eventually be changed. Design #2 First of all, in order to allow immediate motion, I attached the string to a lock washer, preventing it from hitting the outside of the wheel. I also drilled the holes for the axles more and sprayed dry graphite into the holes, making them more slippery and therefore reducing friction. I re-aligned the front wheels using electrical tape in an effort to keep the car in a straight line. Test #2 The car didn't get stuck at the beginning, but it only went for a few feet before stopping. After kicking it a few times, it went for a total of around 25 feet, but it still went left. It did not have a lot of torque either, due to the too-long lever arm. Design #3 I added washers to the axles where lock washers touched the wood, creating less friction. I also changed the lever arm from a dowel rod to a shorter metal bar Test #3 Although the car started immediately, it continued to turn left; the back wheel was not stable enough to keep the car in a straight line. I flipped the car around so that the front wheels became the back wheels, just to see if it would work. The car went perfectly straight for at least 40 feet and would have gone longer if it hadn't run into a wall. Evaluation Although there are very few necessities in building a mousetrap car, getting it to go 35 feet in a straight line requires many adjustments and additions. A three-wheeled vehicle is a great way to lessen the weight of the vehicle, but it can also make the car less stable. If I were to repeat the project, I would probably attempt to use three wheels again, but I would need to use higher-quality and/or more precise tools, in order to prevent the car from going left or right. However, for making a straightforward and stable vehicle, a four-wheeled design is the way to go. Another Test After testing the car at school, it turns out that it wasn't really going straight at all. The back wheel was getting caught in the grooves of my hardwood floor, causing it to appear as if it were going straight, when it really consistently turned right. Design 4? 5? I attempted another 3-wheeled design, using a different large back wheel, but it still continued to turn either right or left. I didn't have precise enough equipment to drill holes for the axles in the exact right place, so a three-wheel design was going to be impossible. Final Design I shifted to a 4-wheel car, simply because I needed the stability and directional certainty that four wheels provided. I used CD wheels to prevent excess friction and reduce weight. I used balsa wood to reduce weight as well, and I used fishing line for the string. Finally, I included two Styrofoam panels underneath the body of the car in order to enhance stability while minimizing weight. Final Test It was very hard to test my car, since the wheels got caught in the grooves on the floor, so I tested it in two places for two different attributes. As far as distance, I tested it on the hardwood floor. It got caught in the grooves, but it went far beyond 35 feet. Then, I tested it in my garage, which has a flat surface, to see if it remained in a straight line. There wasn't a lot of room for distance, but it went straight for the 20 or so feet that it could.
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