Mousetrap Cars Tips
A mousetrap powered car is a vehicle that is powered by the energy of a
wound-up mouse trap's spring. The most basic design is to tie one end of a
string to the tip of a mousetrap's snapper arm and then the other end of the
string has a loop that is designed to "catch" a hook that is glued 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's 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.
To wind the string around the axle, the wheels are turned in the direction
opposite to the motion of the vehicle's travel. It is important that the string
NOT be wound loosely or it will snag itself as it is pulled from the axle by
the lever arm, the string should carefully be wound tight and uniform around
the axle. Do not push on the mousetrap's lever arm during this process, you
want the string to be tight and to pull the lever arm over.
Once the car is released, the string is pulled off the axle it cause the wheels
to rotate propelling the vehicle. If the mousetrap is located to close to the
drive axle the wheels can spin at the start wasting energy.
The first step to making a good mouse trap powered car is simple, put
something together and find out how it works, it may not be pretty but it is a
start. Once you have something working you can begin to isolate the
variables that are affecting the performance and learn to adjust to improve
your results. Building mousetrap cars is a simple process of design
engineering, you build, you test and experiment, you change, and you do it
all over again.
Long lever arms decrease the pulling force and power output but increase
the pulling distance. Short lever arms increase the pulling force and the
power output by decrease the pulling distance but increasing the speed.
If you are building a distance vehicle, you want to minimize the power
output or the transfer of stored potential energy into kinetic energy of motion
at the slowest possible rate. This usually means having a long lever arm and
a large axle-to-wheel ratio. If you make the lever arm too long, you may not
have enough torque through the entire pulling distance to keep the vehicle
moving, in which case you will have to attach the string to a lower point or
change the axle-to wheel ratio
most important is reducing friction, the more you can reduce or eliminate
friction, the farther your racer will travel. In a perfect universe, a mousetrap
vehicle will travel forever, just like an object thrown in space should travel
forever or until it hits something. This is the challenge that makes building
mouse trap powered cars so much fun, seeing who can reduce friction the
most
Greater distance can be achieved by:
• using a longer length lever arm
• having a large axle to large wheel ratio.
• eliminate friction
Ideas for Increasing Distance
Increase Axle-to-Wheel Ratio
1. Use a larger drive wheel. Try making a large wheel out of mat board. Mat
board is stiff and light-weight. The larger your drive-wheel the greater the
distance your mousetrap car will travel per turn of the wheel.
2. Use a smaller drive axle. The larger the ratio of drive wheel(s)-to-axles
diameter, the farther you mousetrap car will go for each turn of the wheel
and the greater the pulling distance will be.