~ What should we use for our mouse trap car, four wheels or 3?
It really depends on what you want more for you car, stability or distance. If you were to go with 3 wheels, there would be less weight, and thus making it easier for the car to travel. At the same time it would also mean less surface friction.
On the other hand if you use 4 wheels, it would mean a more stable car that is equally as good. There is a higher chance of the trajectory of the car being strait without loosing balance. But we then realized that 3 wheels rather than four would mean more wheels to align. So we are caught in a dilemma
We decided to use four wheels because it was too much of a risk to use only three wheels. There would be a lot more work fixing it, if something went wrong using 3 wheels.
~ Larger diameter wheels?
The larger the diameter of the wheel the more mechanical advantage there is. If you think about it this way, if you were to use a small wheel, it would require more energy to work. When instead you could use a wheel with a larger diameter and thus with just one full turn can replace several turns of a small diameter wheel.
We used a wheel with a diameter of 25cm, because we knew that was the smart thing to do.
~ Where do you put the mouse trap on the chassis?
The lever is attached to the mouse trap and what we want is for our car to go the farthest possible. So what's logical is to put our mouse trap furthest up front on our frame as possible.
We put our mouse trap directly in front of our front wheels so now our lever is about 60cm long. That should give us a pretty good distance if all goes well.
~ Our car won't move?
Normally, it is either one of these reasons, there is something wrong with the wheels or/and axle, or there is to much weight.
In our case, it was because the mass of the records (back wheels) was too great that it overcame the kinetic energy of the mouse. So it just won't move. What we did was, Mr. Smith drilled holes into the records, removing a total of about 17 grammes. Every little bit counts!
~ What is a good length for our car?
Generally, the longer the lever the more pulling distance you have. The lever is slightly shorter than the chassis as it has to be perpendicular to the axle of the back wheels.
We weren't quite sure what length we wanted but we settled on a chassis of about 1 m. As we worked it may have gotten shorter along the way. We also attached our mouse trap at the very front end of our frame, so we could use a longer lever.
~Why do the wheels keep wobbling back and worth and how can we fix it?
It is very important that when building a car, the wheels are properly aligned. Otherwise, if the car turns or if there is any excessive movement, there is a waste of energy which could easily been used to give the car more distance.
What we did to prevent the wheels from wobbling was to use triangulation. At the end of our wheels, we added to right angled triangles made from chloroplast and attached it at 90 degrees. That made an improvement, but even now I'm still trying to get the perfect alignment.
