Mousetrap Vehicle Fundamentals
What is a 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 outline the basic concepts needed to consider when creating a mousetrap vehicle and how to optimize those aspects of your device for the best results.
What to consider
Weight
Vehicle weight is an important factor to consider when building your mousetrap vehicle. Depending on the rules of your competition and your available materials to construct your device, the minimum weight you can achieve will vary. However, if there are no restrictions on weight, you should aim to build your device to weigh under 200g (~7 oz).
The greater your mousetrap vehicle weighs, the shorter the distance it will cover and the speed it will travel. This consequence is due to the limited energy within the mousetrap. When the vehicle weighs more, the energy needed to overcome the gravitational energy of the vehicle increases, resulting in less energy available to propel the car forward, in turn, reducing the vehicle’s speed and distance it can travel.
Friction
Friction is an important factor to minimize in any vehicle-based competition, especially in mousetrap vehicle where there is only a limited supply of energy available to power the vehicle. The best solution to minimize friction between the axles and the vehicle frame is to use ball bearings. However, if you are unable to obtain ball bearings, graphite powder, oil, or other lubricants can be used to reduce the friction between the axle and vehicle frame. It is important to note, though, that if no ball bearings are used, you should try to minimize the contact between the axles and the vehicle frame by making the vehicle frame thin in areas where the axles are held.
Drive Axle Diameter
The drive axle is the axle of the mousetrap vehicle that is directly powered by the mousetrap.
The drive axle diameter of your mousetrap vehicle can be addressed in either of two ways depending on what aspect of your vehicle you want to maximize:
If you want to maximize the speed of your device, the drive axle of your vehicle should be larger, which reduces the time required to fully use the mousetrap’s energy, in turn, increasing your vehicle’s speed. However, the distance that your vehicle can travel will be reduced.
If you want to maximize the distance your vehicle can travel, the drive axle of your vehicle should be shorter, which increases the time required to fully use the mousetrap’s energy, in turn, increasing the distance your device can travel. However, the speed of your vehicle will be reduced.
Drive Wheel Diameter
The drive wheel is the wheel of the mousetrap vehicle that is attached to the drive axle.
The drive wheel diameter of your mousetrap vehicle can be addressed in either of two ways depending on what aspect of your vehicle you want to maximize:
If you want to maximize the speed of your device, the drive wheel of your vehicle should be shorter, which reduces the circumference of the drive wheel, resulting in a shorter time period required to fully use all of the mousetrap’s energy. However, the distance that your vehicle can travel will be reduced.
If you want to maximize the distance your vehicle can travel, the drive wheel of your vehicle should be larger, which increases the circumference of the drive wheel, resulting in a longer time period required to fully use all of the mousetrap’s energy. However, the speed of your vehicle will be reduced.
Lever Arm Length
The lever arm of a mousetrap vehicle is the bar attached to the mousetrap that pulls a string attached to the drive axle, powering the vehicle.
The lever arm length of your mousetrap vehicle can be addressed in either of two ways depending on what aspect of your vehicle you want to maximize:
If you want to maximize the speed of your device, the lever arm length of your vehicle should be shorter, which reduces the length of string pulling the drive axle, resulting in a shorter time period required to fully use all of the mousetrap’s energy. However, the distance that your vehicle can travel will be reduced.
If you want to maximize the distance your vehicle can travel, the lever arm length of your vehicle should be larger, which increases length of string pulling the drive axle, resulting in a longer time period required to fully use all of the mousetrap’s energy. However, the speed of your vehicle will be reduced.
Vehicle Length
Vehicle length refers to the distance between the front and back axles.
To maximize your vehicle’s stability, you must optimize the vehicle length of your mousetrap vehicle. This increases the base-area of your device, resulting in a more stable vehicle. It is important to balance vehicle length with your devices weight for the best results.
Vehicle Width
Vehicle width refers to the distance between the wheels attached to a vehicle’s axles.
To maximize your vehicle’s stability, you must optimize the vehicle width of your mousetrap vehicle. This increases the base-area of your device, resulting in a more stable vehicle. It is important to balance vehicle width with your devices weight for the best results.