Design Brief: Mousetrap Racer

Transcription

1 Design Brief: Mousetrap Racer Materials Coping saw Square Pin vise Wood chassis Screw eyes (2 large, 2 small) Sanding block 80 grit sandpaper 5/16 Drill bit Kit of Race Car Parts Hand Tools Sketch Paper (instructor provided) Colored Pencils (instructor provided) Mousetrap Cars: Secrets to Success book (optional) Introduction The Innovate Engineering (IE) Firm is looking for individuals who demonstrate the skills and knowledge to become future engineers. Nate Innovate, the owner of the IE firm, developed a scholarship program for young aspiring engineers and has vowed to pay for their education and guarantee them top jobs in the IE firm when they graduate. The scholarship is only available for the top five finishers in the mousetrap racer challenge. Your challenge is to plan, build, and race (prove) that your design and finished racer is the best. Your task As a future engineer you must be able to develop plans based on research and follow them to completion. Engineers often have to make modifications to their original plans because of factors that may have changed or weren t considered in the original design. Successful engineers keep a design notebook to document ideas, observations, and challenges. This notebook is a resource that helps them reflect and make improvements based on their experience. In addition to the performance of your mousetrap racer, you will be judged on the quality of your design notebook. Your design notebook could be as simple as sketch paper stapled together. Historical research You will need to gather information about possible design ideas. You can revisit the mousetrap racer website or search other websites for more information. 1. What kind of simple machine is the mousetrap racer? 2. Define the following terms and how they relate to the mousetrap racer: Potential energy Kinetic energy Force Friction Torque Power

2 3. What factors can affect the efficiency of the mousetrap racer? (Weight, length of arm, size of wheels, wheel-to-axis ratio, materials used) 4. Define the term mechanical advantage. 5. What are examples of cost effective materials in the construction of a mousetrap racer? Parameters The final presentation must include the following parameters: 1. A design notebook including any research notes and initial sketches of ideas. 2. A final design and list of materials. 3. A written response to the questions in the historical research section. 4. Document challenges faced during the design process and modifications made during the building and testing phase. 5. Visual illustrations to present as a formal presentation to the class. 6. A completed and working mousetrap racer. Note You will be limited to the materials that are provided in the mousetrap racer kit, so use them wisely. Evaluation Your solution will be evaluated based on the following criteria: Criterion Historical Research Sketches and Designs Process and Planning Design Notebook Performance Description Did the team provide adequate responses to the questions in the historical research section? Did the team provide several initial sketches and ideas for the mousetrap racer? Did the team assemble a mousetrap racer according to the final design selected? Did the team document the overall design process, including modifications and testing? Did the team effectively present and communicate their design and was the racer successful?

3 Design Brief: Mousetrap Racer - Chassis Materials Coping saw Square Pin vise Wood chassis Screw eyes (2 large, 2 small) Sanding block 80 grit sandpaper 5/16 drill bit Chassis Note It is important that both axles be square to the base and to each other. 1. Using the square, mark a line at the front and back of the car, to locate the axles about 1 from each end. 2. Draw a line on the bottom of the chassis, 1 from the front. 3. Draw the shape of your car on the top of the chassis. Make sure that the front axle will fit on your design. 4. Using the coping saw carefully cut out the shape of your car. 5. Sand the rough edges of the base with the sanding block. 6. Mark the location of the screw eyes you will be installing for the front and rear axles. The eyes should be at least ½ from the edges of the base. Remember, the front axle will go on the bottom of the car and the rear axle will go on the top of the car. 7. Using the pin vise and drill bit, start a small hole in the base for each screw eye. Only drill in just enough to be able to start the screw eyes. The small eyes are for the front axle and the larger ones for the rear.

4 8. Screw the rear eyes into the chassis until the screw begins to stick out through the bottom of the chassis. 9. Screw the front eyes in until the round part of the eye touches the base. 10. Place a mark 1 ½ from one end of the wooden axle. 11. Using the pin vise and bit, carefully drill a hole through the mark you made on the axle.

5 Design Brief: Mousetrap Racer - Engine Materials Power Arm (12 piece of 1/8 steel rod) 1/8 Collar Hex Key Screwdriver Mousetrap File Screws (2) Wooden Axle Masking Tape Metal Axle Pin Vise 5/16 Drill Bit Hammer Front Wheels (2) Pliers CD Inserts (2) CDs (2) Engine 1. Using the file, remove the burrs from the end of the power arm you are going to bend. Make sure the 1/8 collar slides easily over the short end. 2. Place a mark 2 ¼ inches from the end of the power arm that you removed the burrs from. 3. Using the pair of pliers, bend the end of the power arm to a 90 angle at the 2 ¼ mark. A few degrees past 90 is ok. 4. Unclip the spring from the mousetrap capture bar using the flat screwdriver. 5. Remove the staple holding the bait holder from the mousetrap.

6 6. Remove the bar hold-down arm. 7. Use your thumb to hold the spring down on the mousetrap, and with your other hand, cut the trap arm near the spring. 8. Remove the trap arm sections from each other. Slide out the remaining piece from inside the spring. Make sure you keep holding the spring with your thumb. 9. Slide the short end of the power arm through the eyes on the trap and through the spring. Make sure the long arm of the power bar is closest to the bent part of the spring. You can release your thumb now. 10. Place the collar on the short end of the power arm and tighten the screw with the hex key to keep the power arm from coming out of the spring. 11. Using the screwdriver, carefully slip the end of the spring over the power arm so the power arm is now in tension. You may have to bend the end of the spring so that it stays connected to the power arm. 12. Using the pin vise and drill bit, drill a hole in each end of the mousetrap. 13. Using the screws, attach the mousetrap to the racer. 14. Using the hammer, carefully tap the metal axle into one of the black wheels.

7 15. Insert the axle into the front eyes and then tip the racer on its side. Carefully tap the second wheel onto the axle 16. Snap the CD inserts into the CD s. 17. Using the hammer, carefully tap the wooden axle into one of the CD hubs. 18. Insert the axle into the rear eyes and then tip the racer on its side and carefully tap the second CD hub onto the axle. 19. If you find that the CD slips on the red axle insert, you can add a piece of masking tape to secure them together. Instructor Ask your instructor if you can test your racer on the floor to see if it travels in a straight line. If you have a clear 20 foot space in your classroom, you can use that. If needed, ask your instructor if you can go out into the hall. 20. Give it a push. Your racer should travel in a straight line, at best. Or, at worst, with less than 1 foot movement to the left or right over 20 ft. If your racer veers sharply to the left or right you will need to adjust the placement of the screw eyes on the front and back axles. 21. If your racer veers to the left, move the left screw eye on the front axle forward. If it veers to the right, you need to move the left screw eye backward. You may have to try several times to get your racer to travel in a straight line.

8 Activity: Mousetrap Racer - Final Improvements Materials Fishing Line Masking Tape Tape Measure Scissors Final Improvements 1. Using the measuring tape, cut a piece of fishing line 22 inches long. 2. Take one end of the line and tie a small loop in it. 3. Take the small loop and place it over the very end of the power arm and tape it on to the power arm. Make sure it will not slip down the power arm. 4. Take the other end of the line and slide it through the hole you made in the rear axle so it sticks out about a half inch. 5. Have your partner help you wind the line onto the axle. Begin by rotating the rear axle counterclockwise. As you add wraps to the axle, you will have to move the power arm to release tension as you add more wraps. Continue to add wraps until you are out of line. How you wrap the line can make a difference in how far the car travels. Continue to hold the power arm so it does not release. Instructor Ask your instructor if you can test your racer on the floor to see if it travels in a straight line. If you have a clear 20 foot space in your classroom, you can use that. If needed, ask your instructor if you can go out into the hall.

9 6. Once your racer has stopped, measure the distance with the tape measure and record it. How does the distance match up against your calculated distance in the Activity: Distance Calculation? Record the following in your notebook: Is there a difference between the calculation the and actual distance your mousetrap car traveled? Describe factors that may have affected the theoretical difference and the actual difference your mousetrap car traveled. 7. To increase the distance your racer travels try some of these tweaks. Friction can be your friend or your enemy when building a mousetrap racer. By moving the location of the mousetrap forward or backward you may be able to add to the distance traveled. Sand the edges of the CDs with sandpaper to increase traction if you think your wheels are slipping. Add wide rubber bands to the CD wheels to increase traction. Experiment with how the line winds on the axle. You may be able to wind the line in a way that at the very beginning of the run the car does not accelerate as fast therefore reducing slipping. Add a few drops of light oil to lubricate the contact points between the screw eyes and the axles. Instructor Ask your instructor if you and your partner can race each other or race other classmates. Action Return all tools and materials to their proper location and clean up your area.