Mouse Trap Car
Mouse Trap Car








Mousetrap Racer shown with optional extended arm

A mousetrap-powered racer is a vehicle that is powered by the energy of a wound up mousetrap spring. The most basic design is as follows: one end of a string is tied to the tip of a lever arm that is attached to the mousetrap s snapper arm. The other end of the string has a loop that is designed to catch a hook attached to a drive axle. Once the loop is placed over the axle hook, the string is wound around the drive axle by turning the wheels in the opposite direction to the vehicle intended motion. As the string is wound around the axle by the turning of the wheels, the snapper's lever arm is pulled closer to the drive axle causing the mousetrap spring to wind-up and store energy. When the drive wheels are released, the string is pulled off the drive axle by the mousetrap causing the wheels to rotate.

What you need to build a mouse trap car.
Contents
Wood Chassis (1/4”X2 ½”X12”)
Front Wheels (small)
CD Adapters (Recycle old CD's as wheels)
Metal Axle (1/8”X21/2”)
1 - Metal Rod Arm Extender
Straw
Wood Axle (1/4”X31/2”)
Screw Eyes
Screws
Mouse Trap
Mono-filament Line (Fishing Line)
Brad - Small Nail
Instruction Sheet

Tools Needed:
Hammer
Low Temp Hot Glue Gun and Glue
Pliers
Diagonal Cutting Pliers
Ruler
Pencil
Screw Driver
Scissors
Saw

Safety First:

Be careful and avoid injury when working with hammers, saws or any other hand or power tools.
The mouse trap has a spring which when released could be dangerous and might cause injury if not used with care.

Objectives -

In utilizing this kit students will:

• Design a mouse trap powered vehicle

• Work with tools to process materials and assemble a product

• Incorporate problem solving techniques
• Apply mathematical calculations and measurement • Utilize scientific inquiry

Design Challenge
Students will design and construct a mousetrap powered vehicle that will -travel the greatest distance.

Constraints:
Student may use materials supplied in the kit
Student may supply other materials approved by the instructor
A time limit may be set by the instructor
Only one mousetrap may be used as the source of propulsion
The spring of the mousetrap may not be altered in any way (This is a safety precaution.  Winding the spring tighter can result in the spring breaking.)
The mousetrap must move forward with the vehicle.  The mousetrap cannot be used to anything but the vehicle.

Basic Assembly Information:

Read all instructions first
Identify each of the components in the kit and the purpose it will serve
Draw preliminary sketches for the car design showing location of components and how it will work
Select the best design from your preliminary sketches
Draw a plan of your car either full size or half scale
Cut the chassis to the appropriate size and shape to fit the front axle


Cut the straw to length to serve as a bushing for the front axle (two small screw eyes are provided they can used instead of straw)
Locate and hot glue the straw in place, install the axle and mount the wheels (make sure the axle is straight so car will travel in a straight line)

To install the back axle measure and mark the location for the screw eyes on the top rear of the chassis (they will serve as axle holders)

One of the scrap pieces cut from the front could be glued where the screw eyes will be inserted to add thickness to the chassis at this point (this might prevent the tip of the screw eye from sticking out and causing possible injury)


To install the back axle measure and mark the location for the screw eyes on the top rear of the chassis (they will serve as axle holders)
Screw the 2 - screw eyes into place (make sure they are aligned so the car will track properly)Insert the back axle in the screw eyes and tap the nail into the axle between the screw eyes about 1/2"  from either one (pre-drilling may help to prevent splitting)

              

Using the diagonal cutting pliers cut off the nail head leaving approximately 3/16"

While the axle is on the car put CD wheels in place, but first install the inserts




Using the screws provided attach the mouse trap to the car body (pre-drilling wholes for nails or screws may prevent splitting)  Hot glue maybe used instead.

The mousetrap car can be operated by attaching the string directly to the top of the trapping mechanism  or use the alternate method mentioned below.


    Alternate Method

    A rod can be attached to the mousetrap to increase leverage, you may come up with your own method or use the one described below

Bend the rod to an "L" shape.

           

Pry off the catch and the holding bar from the trap leaving only the spring and the trapping mechanism (it is important that you keep your finger on the spring while removing the trapping mechanism to avoid unwinding the spring)

Insert the straight part of the rod through the holder and the spring


Tie the end of the rod with two small wire ties.  Then secure it in place with some duct tape.

Take the other side of the fish line and make a loop at the end, tie a knot and cut the excess line

Operation:

Hook the loop of the fishing line to the pin on the axle and reverse wind the rear wheels (keeping the line taught while winding the spring back)
Hold the rod and axle so it will not release until you are ready to run the car.
Run the mouse trap vehicle on the floor
Make adjustments to your design in order to make it travel the greatest distance




Performance Tips:

There are MANY things that can be done to a mousetrap-powered racer to change the speed and/or distance of traveling. Try to find a harmonious balance between improvements that have a positive effect on the performance of your racer, experimenting and testing is the key to success.

Do not put slack in the string as it is wound around the drive axle by holding down on the mousetrap. The string should be pulled tightly -by the mousetrap-lever as it is wound around the axle.

The string should be just long enough to reach from the tip of the lever arm to the drive axle's hook.  If the string is too long it will not fully unwind from the drive axle causing it to tangle around the drive axle then stopping the vehicles motion.

Graphite powder will reduce the friction on those moving parts where it is applied causing the vehicle to move faster and farther. Use graphite powder between ALL moving parts that touch one another.

Straighten out the wheels so they do not wobble. Not all the rubber spacers are the same; some holes might be off center, experiment with the rubber spacers by switch them out in order to find which ones work best with the wheels and produce the smoothest ride.

If a vehicle is spinning-out at the start try the following trick: cut out the middle section of a balloon so that it forms a band that can be stretched around the outer edge of a wheel. Use ONLY on the drive wheels in order to keep the rotation inertia law.

This is a GREAT race time tip for a vehicle that needs a little extra speed or torque; wrap masking tape around the drive axle, a thicker drive axle will generate more torque and/or speed. Make sure that each wrap of tape goes on smoothly and tightly, you will have to attach a new axle hook over the tape. If your vehicle is spinning out after adding the tape, try removing some of the layers of tape.

Steering can be a big problem and there are several reasons why a vehicle may not travel straight, courses might be sloped and/or have bumps that throw-off a vehicles line of travel, a vehicle s axles might not be aligned with one-another causing it to drift towards one direction. Unless your vehicle has adjustable steering there is little that can be done to change the alignment of an assembled vehicle. Learn to play the curve! If a car curves to the right, start the car on the right hand side of the course and aim it towards the left side in order to obtain the largest possible arc of travel. Find out where to start your racer along the start line and in which direction it should be aimed in order to obtain maximum results.








Mouse Trap Car
Score Sheet
Student Name:
CATEGORY
            601
            40
             30
            20
Function
Vehicle functions
Vehicle functions well,
Vehicle functions
Fatal flaws in function
extraordinarily well,
traveling a distance of
pretty well, traveling
Travels less than 5
traveling a distance of
10 feet or more in a
5 feet or more
Feet or is immobile.
15 feet or more in a
straight line.
in a straight line.
relatively straight line.
Construction -
Great care taken in
Construction was
Construction
Construction appears
Care Taken
construction process
careful and accurate
accurately followed
careless or
so that the vehicle is
for the most part, but
the plans, but 3-4
haphazard. Many
neat, attractive and
1-2 details could have
details could have
details need
follows plans
been refined for a
been refined for a
refinement for a
accurately.
more attractive
more attractive
strong or attractive
product.
product.
product.
Aesthetics
All of the vehicle is
Some of the vehicle is
Some of the vehicle is
None of the vehicle is
extremely well-
well-decorated with
well-decorated but the
Decorated and students
decorated with
student name
student name is not
Name  is not provided.
student name
provided.
provided.
provided.


Total Score: -----------



Applied Technology - Blanchester High School