1. Mousetrap Cars
A basic and refresher workshop for this Mechanical Engineering Challenge

2. Bonus Points for whoever knows this game…!!!
OK… Now Let’s Dig In…!!!
Bonus Points for whoever knows this game…!!!

3. What is a Mousetrap Car?
A mousetrap powered car is a vehicle that uses a mouse trap for a motor and a string to transmit force. In this method one end of a string is attached or tied to the arm/bail on the mousetrap and the other end of the string is wound around an axle.
By winding the string around the axle, the mouse-trap's spring is wound creating stored/potential energy. When the mousetrap car is released the mousetrap’s spring unwinds the string off of the axle causing the wheels to turn and off the vehicle goes.

4. Purpose & Objectives of this Session
Encourage and promote the integration of STEM standards into the building and designing processes of the mousetrap car
Explain Guidelines of the competition
Help you teach your students:
Problems solving skills
How to budget their time
Cooperative behavior
Engineering and design concepts
Let’s Focus On

5. STEM [ideas] of Mousetrap Cars
Torque
Potential & Kinetic Energy
Speed
Wind drag
Rolling Friction
Rotational Inertia
Scientific Inquiry
Science
Tradeoff Concepts
Simple Machines
Materials
Research
Build Techniques
Technology
Redesign
Troubleshooting
Testing
Assembly
Design Processes
Engineering
Measurements
Manipulating variables to Maximize F (See Formula)
Manipulating variables to maximize N (See Formula)
Mathematics

6. Building a Winning Team
A “Solid” SECME Mousetrap Car team is composed of a combination of students with different skills and abilities i.e.
Researcher / Planner
Drafter / Designer
Builder / Tester
The coordinator should monitor student progress to assure that they understand the STEM concepts, follow the guidelines, and meet deadlines.

7. Calculating the Score [Overall]
The overall team score in the competition is a sum of the following:
Performance (car run) using formulas (next slide) > [Max 100 points]
Technical Report > [Max 100 points]
Design Drawing > [Max 50 points]
Team Interview > [Max 50 points]

8. Evaluation Guidelines
REQUIREMENTS
Each Mousetrap Car Engineering Design team must have three (3) students & competition requires participation in these four areas:
Mousetrap Car Construction and Run
Technical Report on Mousetrap Car
Design Drawing of Mousetrap Car
Team Interview with Judges

9. Evaluation Guidelines
CAR CONSTRUCTION AND DESIGN
This is an overview [* * *Read Official Guidelines Carefully* * *]
A standard mousetrap MUST be used (4.5x10cm & ~ 25g)
Understand the components of a standard mousetrap
The mousetrap spring must be the sole power source
Original mousetrap spring and base must remain intact and unaltered. Locking lever and bait holder may be removed. Bail may be straightened but unaltered.
NOTE: For experienced builders, gears & pulleys are allowed as long as ALL the other guidelines are adhered to.

10. Evaluation Guidelines (cont)
CAR CONSTRUCTION AND DESIGN
This is an overview [* * *Read Official Guidelines Carefully* * *]
The spring must be visible and/or accessible for judges.
The car must have a minimal of 3 wheels
Cars will be tested on a smooth flat surface. Distance is measured from the farthest point of travel, utilizing a straight line to connect the two points.
There will be two (2) runs for each car; the better perfomance run will be used for the final scoring

11. Standard Mousetrap Diagram

12. Calculating the Score [Performance]
It’s time to some numbers…!
Two (2) formulas are used to calculate the Performance score for the car’s run:
I’m getting hungry…!

13. Solving for N w = mass of the mousetrap (25 grams)
W = total mass of completed car (in grams)
D = distance (measured in a straight line from starting point to stopping point in centimeters)
L = length of car in centimeters (furthest of front to furthest of rear)
T = time (seconds) cars travels from start to stop
N = Performance score

14. Solving for F N = Performance score from
NL = maximum performance score of all cars
F = Final Performance score (to be combined with Technical Report, Design Drawing, and Team Interview scores)

15. Key Points to Consider with (W)
A good mousetrap car is designed around the two (2) formulas and not around just how far it can go.
W = total mass of completed car (grams)
Your goal is for the total mass/weight of the car to be as LOW as possible and can be achieved by:
Decreasing the mass of the wheels (cut out insides)
Choosing light building materials (glue, tape, foam, etc.)
Minimize decorative paint, tape, stickers, etc.

16. Key Points to Consider with (D)
D = distance (measured in centimeters)
Your goal is for the mousetrap car to travel as far as possible… In a straight line…!
Regardless of the car’s path, the value of D is measured from the starting point to the end point utilizing a straight line. In the examples below, A and B are the start and end points, respectively, with D being the actual distance.
NOTE: There are NO required minimum or maximum distance(s) to travel

17. Key Points to Consider with (L)
L = Longest dimension of the car (from the furthest of front to furthest of rear) measured in centimeters
Your goal is the minimize the longest dimension of the car while retaining the properties that make it perform well

18. Key Points to Consider with (T)
T = Time (measured in seconds)
Your goal is for the mousetrap car to travel as fast as possible… In a straight line…!
Speed is calculated as distance divided by time. Your goal is for the car to not only travel as far as possible (distance) but to also arrive at your maximum distance with the lowest time which essentially means the cars is FAST…

19. Now Let’s Dive Into Some Examples…

20. Analysis of Mass Calculation (W)
W = 45 grams
W = 40 grams
N = (.625) x (250) + (250)
N =
N =
N = (.555) x (250) + (250)
N =
N =
A small decrease of 5 grams of (W) increases the (N) value by 4.47%

21. Analysis of Time Calculation (L)
L = 15 cm
L = 10 cm
N = (.625) x (166.66) + (250)
N = (.625) x (250) + (250)
N =
N =
N =
N =
When the longest dimension (L) of the car is decreased by 5 cm, (N) increases by 14.7%...!

22. Analysis of Time Calculation (T) (D/T = Speed)
T = 15 sec
T = 10 sec
N = (.625) x (250)
N = (.625) x (250) + (250)
N =
N =
N =
N =
If you decrease (T) by 5 seconds your (N) value increases by 25.81%...! Speed Up…!!!

23. Technical Report Guidelines
As a part of the Design Competition, the team is required to write a Technical Report describing the design, construction, and operation of the Mousetrap Car. Parts of the Technical Report are:
Cover Page
Abstract
Contents
Introduction
Design
NOTE: Please see Official Guidelines for specific details
Construction Procedure
Operation
Conclusion/Recommendations
Acknowledgements (Optional)
Appendix (sketches, tables, and charts
ALSO NOTE: Take EXTREME caution regarding plagiarism

24. Design Drawing Guidelines
The mousetrap car drawing in required to illustrate the actual car built (photographs or computer generated drawings will NOT be allowed).
The size of the engineering paper is to be the standard 18” x 24”, plain, non-grid, 17 pound vellum sheet. Allow the required 1” border on all sides. Actual drawing is to cover an exposed area of 16” x 22” of the paper. NO MOUNTING OR FRAMES BUT DRAWING MAY BE LAMINATED FOR PROTECTION IF DESIRED.
All dimensions are required to be illustrated on the drawing

25. Design Drawing Guidelines
4) The scale and the units are required to be indicated on the drawing
5) The team’s Mousetrap Car Drawing is required to show front, side, and top views
6) All parts of the car are required to be labeled.
7) Ink pens, pencils or markers may be used

26. Design Drawing Guidelines
8) The title legend is to be drawn in the bottom left corner of the drawing inside the 1” border with the following information:
Team name
School Name
School District
Team Member’s Names and Grade Levels
School Coordinator’s Name
Date of Competition
AT ALL COMPETITIONS, THE MOUSETRAP CAR DRAWING WILL BE JUDGED ON: (See guidelines for details)
1) RESEMBLENCE (Between the actual mousetrap car and drawing)
2) SCALE
3) NAMING/LABELING (of all of the parts used)
4) APPERANCE/NEATNESS

27. NOTE: Please see Official Guidelines for specific details
Team Interview
Each student team will be interview by a panel of judges discussing the car’s design and testing as well as the Design Drawing & Technical Report
Team members are interviewed as a group
Each member is expected to be able to serve as spokesperson
The interview will be conducted apart from the performance and scoring of car
NOTE: Please see Official Guidelines for specific details

28. Team Interview
The interview will take place between the Design Drawing and Technical Report scoring and performance runs
The interview will be one element in arriving at the overall score in competition.
The Team Interview will be judged on:
- Teamwork
- Application of Technical Principles
- Knowledge of Design
- Oral Communication Skills

29. Final Key Points
Teachers should focus on STEM standards along with the design and build of Mousetrap Cars
Teachers should ensure that students design, build, test, troubleshoot and rebuild as much as necessary to thoroughly grasp the STEM concepts regarding Mousetrap Cars in order to be ready for both Regional and National Competition
Students should design and build their cars around the formulas to:
Minimize the total mass of the car (W)
Maximize the distance car travels in a straight line (D)
Minimize the size of the car (L)
Minimize the Time (T)… FAST CAR…!
Remember… STEM, STEM, STEM…!!!

30. One Last Thing
Please visit the National SECME website’s for more information and details and at
Educational Resources – STEM National Standards
Please enjoy some pictures on the next 4 slides…!

31. Pictures of Mousetrap Cars

32. Pictures of Mousetrap Cars
Decrease the mass of the wheels by cutting out the insides of large wheels

33. Pictures of Mousetrap Cars

34. Pictures of Mousetrap Cars
The End Thank You…!!!