How Can Mousetraps Be Used to Power Cars for Distance?

In this world there are many different variations in how energy takes form. Energy is power which is aquired from many different means, both chemical and physical. It can never be created, nor be destroyed; instead it is passed through states as it partakes in an endless cycle of it being used and stored over and over again. Whilst many different types of energy exist, there are two main categories which they are sorted, kinetic and potential. Kinetic energy refers to, in essence, the energy used in motion. On the otherhand, potential energy is energy stored in an object. There is a stark difference between the two, however, they inevitably are transformed into each other through energy conversion. When potential energy is eventually used it will become kinetic energy, and when kinetic energy is 'used up' and stored, it takes the form of potential energy. With the existence of these two principles, many ideas and projects arise.

One extremely popular project is that of mousetrap cars, which are commonly constructed as school assignments. Mousetrap cars cover the topics of physics, engineering and mathematics and, when done right, can reach long distances and high speeds. The potential energy stored within the mousetrap spring is transformed into kinetic energy as the snap arm pulls. It is then powered and propelled forward as the axle is rotated via the attached string. Another significant element which must be considered when constructing mousetrap cars is the presence of friction. This force refers to the resistance encountered when two objects slide against each other, and can make movement difficult. Friction can never be fully removed, but for the mousetrap car project it must be reduced in order for the vehicle to run smoothly, and for less wasted kinetic energy.

Supplies

Four DVDs for wheels
Two smooth pencils for axles
Wooden rulers for frame
- Two full size, eight half size
Eight washers
Hot glue
Screws
Mousetrap
Graphite powder
Dowel for snap arm
Cotton string
Zip ties
Sandpaper to smooth axles
Paint (optional)

The method is as follows...

Design

The first step of this project is to design the mousetrap car. This requires a basic understanding of energy and motion, which was covered in the introduction. In order to design the car, sketched must be made until the final solution is found. It is in this step when the materials needed are brainstormed

Constructing the Frame

The frame is the fundamental base of the car, it is important to keep it light yet strong so the car can perform the best it can. The frame is made of two and several half sized wooden rulers.

The first step is to drill holes into each end of both the standard rulers, approximately 2 centimetres inwards. Make sure the holes align as this will be where the axles go through. Next, using hot glue, begin to build the frame. Make a rectangle using the two standard and two of the half sized rulers. Begin to reinforce the frame by gluing half ruler through the middle and on each end.

Dedicate one end to be the back of the car; this will be where the mousetrap will eventually sit. Use three half rulers to make a box shape, and lie another one horizontally to make a 'bed' for the mousetrap to lie on. Reinforce the front of the car with the last remaining ruler.

Now that the frame has been built, decorate the car with paint.

The Wheels

This mousetrap car, as with many, uses DVDs for the wheels.

First of all, paint one side of the wheels and allow them to try. This may take some time, depending on the type of paint. Spray paint is the most effective.

Once dried, glue washers onto the unpainted sides, making sure to align the holes. Why more washers? Washers have smooth surfaces and when the wheels rotate, intead of rubbing against wood it will be the washers turning against each other, creating minimal friction.

Creating the Axle

The axles are what allows the wheels to turn, and for this project will be created with two pencils. Dowels could be used instead, as long as they fit. The axle at the front will be what is controlled by the mousetrap.

To create the axle at the back of the car. Simply cut it to size, put it through the holes in the fram and glue to wheels onto it. Do not glue the wheels directly onto the frame, or else they won't be able to spin. Take care to centre the axle and the wheels properly to allow the car to move efficiently.

Next is the driving axle. Cut to size and sand down the majority of the axle until there is a noticeable difference, leaving about 2.5 centimetres on each end so it can fit snugly into the wheels. Repeat the glueing process, making sure the wheels align, and tighten a cable tie around one end of the driving axle. This will be where the string will catch. Snip the excess length of the cable tie and apply graphite powder to reduce friction.

Attaching the Mousetrap + the Snap Arm

The mousetrap is the engine of this project. A first optional step would be to cut away the parts of the mosetrap where the snap arm will go, to allow an extra turn or so.

Drill small holes through the platform at the end of the car where the mousetrap will sit, and drill part the way through the corners of the mousetrap. Position the mousetrap to be as far back as possible and using the holes, screw the mousetrap onto the platform. To add extra reinforcement, add some glue.

Next, cut a 31 centimetre length of dowel, this dowel will be the length of the car. Attach this to the bar of the mousetrap using three cable ties and extra hot glue for support. Cut a length of string and create a small loop at the end of it. Tie the string onto to end of the dowel and hook it around the catch on the dtiving axle.

The Final Stage

This is the finishing touches that will turn a good car into a great car.

Test the car and watch how it runs. Notice if there are any imperfections, do the wheels wobble? Does it stop too soon? Identify where these issues stem from (often the wheels aren't aligned correctly, or the frame isn't straight) and fix it. Projects like these require a lot of trial and error.

Repaint any areas or smooth out any rough bits in order to make it look appealing too.

Results and Conclusion

Results:

Test 1. 15 metres

Test 2. 17.8 metres

Test 3. 15.5 metres

Average. 16.1 metres

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The construction of this mousetrap car resulted in an overall success as it achieved a maximum distance of 17.8 metres, which is a fantastic result. It was able to perform as it was meant to, achieving the aim of creating a mousetrap car able to travel the furthest distance possible. This was made possible due to many trials made during the design process, allowing the car to fulfill its expectations. Despite the outstanding results, there were a couple of issues which, if given more times, could be resolved in order for a more effective car.

When testing it became evident that the car did not run straight, resulting in it colliding into the wall during the first and last test. It would swerve to the right due to a 'wobble' in the back right wheel, which was caused by a tilt in the axle and washer. This could be resolved by gluing it back on straight so that it would run smoother. This issue would have likely also wasted some energy, causing it to reach a lesser distance. Another improvement would be decreasing the weight so that the car picks up more speed and therefore is able to travel further due to momentum. However, the car was already built with minimal weight which means if weight was further reduced, there is a possibility that the stricture would not be as strong. A final improvement would be to increase traction on the wheels by using rubber bands. It was observed that the mousetrap car was not able to drive as well on certain surfaces, such as concrete, possibly as a result of lack of traction. The rubber bands would have allowed the car to grip onto these surfaces better, although this would have also generated more friction.

As seen in the videos, the car was able to run well, however, it was required to start the car at an angle in order for it to not swerve and hit the wall. The videos were of tests one and three and were both cut short as in both tests they eventually collided with the wall, despite the precautions made.

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How Can Mousetraps Be Used to Power Cars for Distance? - Step #7