Mousetrap Powered Car

 Introduction: 

Making a mousetrap car is a mechanical engineering challenge often used as a competition for students from 5th grade up to the second year college.

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 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 stretched and now you have your stored energy. As the mousetrap car is released the mouse trap pulls the string off of the axle causing the wheels to turn and off the vehicle goes.

Some students may prefer to cut all the woods themselves and design their own car; however, most students and teachers prefer to get all the parts in a kit and make changes as they need.

With this project students can explore:

  • A simple propulsion method
  • Basic gluing techniques and design concepts
  • Concept of stored energy

Items Needed:

Mousetrap Car Kits usually come with parts, cut to size and ready to use. The picture bellow shows the materials you usually find in a mousetrap car kit from MiniScience. Kit includes at least 16 wooden parts cut to size in addition to the mousetrap, string, rubber bands and eyelets.

Materials Checklist:

Before using the kit please verify the content with the parts in this picture.

In addition to the kit parts you will need:

  • White glue or wood glue
  • Grip Pins
  • Sand Paper (Medium Grit)
  • Tape
  • Latex Paint

 Teacher Preparation:

During construction of the mousetrap vehicle, students can experiment and comprehend methods of power transfer, using glue, sanding, painting . It is up to the teacher to make sure this background information is provided to students in some manner.

Background

Before invention of gas engines, cars were pulled by horses or other animals. Now gas burning engines are the most popular drive in cars. Inside the engine, the chemical energy stored in fuels are released in the form of hot gases and convert to mechanical force in cylinders.

During the history many other attempts have been made to use other forms of energy to drive a car. In this experiment we try to use the energy stored in a spring (Mousetrap String) to drive a model car.

Assembly Procedure

Prepare your workplace by mounting a cardboard and a wax paper on the top of it. This will protect your environment or desk to be damaged by pins, glue or pint. 

Remove sides and floor parts from the die-cut sheets. Apply glue to all sides and floor where they contact each other, and pin in place as shown.
Apply glue to surfaces of back panel and nose block where surfaces contact sides, and pin as shown. Allow the glue to dry thoroughly. Use sandpaper to sand off top edge of nose block.
Glue aerodynamic wing into notches at rear of sides. Pin in place until dry. Now is the time to pint and apply numbers, names, etc. to your racer before proceeding to the next step.
Push eyelets slowly into sides while holding fingertips over inside hole to help prevent splintering of the wood when eyelet comes through the inside.
Wrap a piece of sandpaper around an axle and use it as a file to create a notch in the short dowel rod, as shown. After notching, set aside until needed later.
Insert the axles into the sides. Axles must rotate freely in eyelets. If necessary, remove axle, sandpaper it until round and smooth, and test it again.

Take the remaining four eyelets and slide onto axles, as shown. Be sure the same amount of axle is sticking out of eyelets on each side. There should be a slight gap between the eyelets, as shown.

Glue eyelets to axle as shown.

Assemble the rear wheels, gluing the die-cut parts as shown.

Carefully press wheels onto axles. The axles must stick through the wheels about 1/8". Place a drop of glue on axles on both sides of the wheels. Spin wheels to check for wheel wobble and adjust before glue dies.
Glue the mousetrap to the floor. You can now paint the wheels if desired.
Apply glue in notch of the small wood dowel and press against rear axle until glue sets.

Note: Apply a second coat of glue around joint after first coat is thoroughly dry. 

Tie string to the trap bail and glue. Tie an approximately 1/2" loop at end of string and glue. This slips over the short dowel rod. Stretch rubber bands (Tires) around rear wheels.

Set the mousetrap to power your racer. (Adult Supervision required to set trap)

A. Lay catch arm of mousetrap on aerodynamic wing. Place loop over end of notched dowel. B. Lift trap bail rearward and press it flush against the wood of the mousetrap while turning rear wheels backward to wind the string around the rear axle.
Keeping fingers clear of the area where the trap bail strikes the wood of the trap, bring catch arm forward and position it under the catch plate and carefully release it so that it is held down by the catch plate.

To release the energy, now stored in the spring supplying power to your racer, press the catch plate with a stick, pen, ruler or similar item. NOT A FINGER. and quickly withdraw the item you used.

If you don't have this kit, you can order it now! It is available both as a single pack and class pack.


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