mousetrap cars and vehicles

Mouse Trap Car - Distance Travelers Picture Gallery

Updated Feb 02, 2005

• pictures of distance-travelers (all pictures are of students cars)

If you are trying to build a long distance traveling vehicle you will need to think carefully about the following concepts: Energy, Power Output, Inertia, rotational inertia, friction, torque, and pulling force.

Energy is what moves your vehicle. The energy of the mouse trap racer is originally stored in the potential energy of the wound-up mouse trap's spring. The spring releases its energy and the potential energy is changed into kinetic energy of motion. Along the way energy is lost to the surroundings in the form of work (heat and sound). The idea is to reduce the amount of energy that is lost over a long distance which will extend the travel distance.

Power output is how quickly the energy stored in the mouse trap is released. There are really only two approaches to this consider when building your vehicle for distance:

• Build a fast moving car the releases its energy quickly and then coast as far as possible or

• Build a slow moving car that releases its energy slowly over the entire pulling distance, this type of car will not coast very far.

Inertia is the resistance that an object has to a change in its state of motion, the more inertia an object has the more force that will be required to change is state of motion. A heavy car will required more pulling force than a lighter car for equal acceleration; therefor, lighter cars will be easier to accelerate but ideally will have less coasting distance that a heavy car at the same speed.

Rotational inertia is the resistance that a wheel or rotation object has to changing its state of rotation. Similar to inertia but dealing with a rotating object. The less rotational inertia that an object (wheel) has the less the torque that will be needed to change its state of rotation or the easier it will be to accelerate.

There are two types of friction, surface friction and fluid friction. Surface friction is caused by the rubbing of two surfaces in contact with on another. Where your axle connects to the frame of your vehicle is one place that you will find surface friction on your car. By reducing the surface friction with graphite powered or ball bearings you will see an increased performance with your vehicle. Traction is a wanted surface friction that is between your vehicles wheels and the flooring, increasing your tracking will allow for greater accelerations because it will take more torque to make the wheels spin out or break loose. Fluid friction is caused by an object trying to move the air out of the way. Make your car aerodynamic so that it is easier to push the air aside.

Torque depends on the length of your mouse trap cars lever arm and the strength of the mouse trap's spring. A long lever arm has the same torque as a shorter arm. The difference between a long lever arm and a short lever arm is that you get more pulling force with a short arm than a long arm. To maximize your acceleration you want a shorter lever arm. Keep in mind that if your arm is too short the force will be large enough to cause the wheels to spin-out, wasting energy. To minimize your acceleration you will want a longer lever arm.

Slow Moving vs. Fast Moving mouse trap vehicle Here are my thoughts on the ultimate distance vehicle. In sharing my thoughts with you please understand that I am not telling you how to build the perfect Distance Car but I am pointing out the application of physics as I applied it to my mousetrap powered vehicles. I tend to design my distance cars to travel extremely slow. One of my cars that travels 100 meters or more may take over 5 minutes to travel that distance. My idea is to reduce the power output to a minimum, only supplying enough energy to the vehicle to overcome the friction. By traveling slowly you will reduce the air resistance to a minimum vs. a fast traveling car that will have more air friction acting against it. Also, I feel that a quick accelerating car will create more heat energy during a quick acceleration than a slow accelerating vehicle which will reduce the energy needed to travel a great distance. Building a mouse trap car for distance means minimizing the wasted energy and converting more energy into displacement of the vehicle. With that in mind, I like to build cars that have very low frictional forces acting against them and move slowly. I try to find a harmonious balance between the movement of my vehicle and the length of the lever arm. My cars tend to have long lever arms and large wheels. If a lever arm is too long the vehicle will not travel the full distance because you must have enough torque to keep the car going and the torque changes with spring angle.

See the following related articles to get started:

• how to make a mousetrap powered vehicle
• making a good distance traveler
• making a good speed-trap racer