How To Increase The Speed Of A Mousetrap Vehicle
What is mousetrap vehicle
A mousetrap vehicle is model car that is powered by mousetraps. Many science and engineering competitions, such as Science Olympiad and SECME, host mousetrap vehicle competitions to help teach basic physic concepts to students.
In this post, we will discuss how to specifically tailor your car to travel at a faster speed.
how to increase speed
Weight
Reducing weight is the simplest way to both increase speed and distance that your mousetrap vehicle can travel. This is because of the power to weight ratio, which is the proportion between the energy a vehicle has and the weight of that vehicle. The greater that proportion is, the lower the car’s weigh is and it, therefore, will travel faster.
Wheel diameter
Refining your car for speed is all about reducing the mechanical advantage of your car. Mechanical advantage is the “ratio of the force produced by a machine to the force applied to it, used in assessing the performance of a machine”. The lower your mechanical advantage is, the faster your car will go, but at the cost of distance.
If you want to reduce the mechanical advantage of your car, then you can simply reduce the wheel diameter of your drive axle. This is because when you reduce the diameter of the drive wheel, the distance the vehicle can travel per rotation of the axle is reduced, allowing energy to be used faster.
Additionally, having a large wheel diameter often leads to high rotational inertia, which is “how difficult it is to change the rotational velocity of the object around a given rotational axis”. Therefore, if you reduce rotational inertia, through the reduction of wheel diameter, you car will travel faster.
drive axle diameter
Similar to wheel diameter, increasing the drive axle diameter will increase your car’s speed because it reduces mechanical advantage.
When you increase the drive axle diameter of your car, the amount of string rotations that can be wound onto the axle are reduced, which, in turn, reduces the time necessary to use all of the mousetrap’s energy. Therefore, if you are unable to change the wheel diameter of your car, you can achieve a similar effect by adjusting the drive wheel diameter.
lever arm length
When you design a mousetrap car, you usually add a lever arm to the mousetrap car to extend the rotational distance the entire mousetrap bar travels. If you haven’t realized it yet, increasing the length of the lever arm attached to the mousetrap, increases the total mechanical advantage of the car. Therefore, to increase your car’s speed, you can reduce the length of the lever arm attached to the mousetrap.
friction
Similar to weight, reducing your vehicle’s friction will both increase speed and distance. This is because by reducing the friction of your vehicle, the amount of energy that is wasted into heat is reduced, allowing your vehicle to utilize that extra energy to travel faster and further. A simple way to reduce friction is to use ball bearings on the axles.