Mousetrap Cars Helpful Hints

There are many approaches to building a mousetrap car. Ultimately the design should reflect the performance requirements. Students usually take two approaches to designing a car that is required to travel the greatest distance possible.

• The first approach is a small light weight car that has a very short lever arm that snaps quickly. In this scenario, the mousetrap imparts its energy to the car very quickly. The car travels at a rather high speed and coasts to a stop.
  
• The second approach is extending the lever arm. This slows the speed of the lever arm but allows a longer pull time on the axle.
  
  

Construction Hints and Tips

Other items to consider:

• An introduction to simple machines and mechanical advantage will benefit the students greatly.

	Wrapping the string around the axle can be troublesome. It requires some practice and patience. Demonstrate to the students how it is done. (Hold the string tightly against the drive axle and begin wrapping the string. This will pull the mousetrap lever arm back. You may need to pull it back as you wind it up.)
	The car does not have to use string to propel itself. Models can be designed to push against the floor to move the car forward.
	Try to encourage creativity. For example, the car does not have to have four wheels. Three and two wheel models work very well if designed properly.

Building a basic mousetrap car:

See materials section for the items you will need. For a first time builder we highly recommend using ice cream push up axles and cylinders. Ice cream push ups are sold in grocery stores. Each push up has an axle and one wheel. You will need two axles and four wheels.

	Step 1-Attach two craft sticks to the posterior end of the mousetrap (See pict 1) Use glue or duct tape to attach the sticks to the mousetrap. The craft sticks make the body longer allowing the back wheels to be set further away. This permits you to increase the mechanical advantage by using larger diameter wheels. Make sure there is a good amount of space between the craft sticks. You will need this space to wind the string around the axle. Balsa wood or any other light weight wood may be used for this purpose. If you use balsa wood, you will need to cut a slot to access the axle.
	Step 2-Tape a soda straw to the anterior end of the mousetrap. The straw should be slightly wider than the mousetrap. The soda straw acts as a housing in which the axle from the ice cream push-up may spin.
	Step 3-Attach a straw to the end of the craft sticks. Cut away the inside material between the craft sticks leaving two short straw pieces.
	Step 4-Extend the lever arm of the mousetrap by attaching a 5-8 inch dowel rod or pencil to the arm using duct tape.The extension must remain rigid (not bend) after it is taped.
	Step 5-Attach two of the ice cream push up wheels to larger wheels such as cd's. Duct tape works well for this. These wheels will be the back or drive wheels of the car.
	Step 6-Slide an axle through the anterior straw and attach the two small ice cream push up wheels. Slide another axle through the posterior straws and attach the larger wheels.
	Step 7-Attach a string from the end of the lever arm. The string should extend just past the drive axle (posterior axle). The string should not be tied to the axle. If it is, it will act as a break.
	Step 8-Hold the string tightly against the drive axle and begin wrapping the string. This will pull the mousetrap lever arm back. You may need to pull it back as you wind it up.
	Step 9-Set the car down and release the lever arm.

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