5 Discussion and Conclusions
5.1 Key findings
We found that having a lightweight chassis and structure aids in allowing the car to move further, as less energy is needed to overcome inertia. However, at certain points of the car (back wheel area), it is essential to increase the mass of the drive wheels. Despite needing more energy initially to overcome inertia, it allows the car to travel a further distance during coasting. The back wheels are hence larger and heavier than the front wheels. The drive wheels are especially important, as they influence the motion of the car. They are required to have traction with the ground, allowing less energy to be wasted on drifting or rotation of wheels on the spot. The wheels also have to be straight and perpendicular to the ground to ensure that the car goes straight. Due to such features, it is necessary for the drive wheels to be well-crafted in order to complement the front wheels, which move in accordance to the drive wheels.
5.2 Comparisons with other designs based on research
A notable design which is feasible and efficient is the use of a teardrop-shaped structure. It features only three wheels in a design known as a “trike” design. With two wheels at the front and one wheel at the rear, it poses an aerodynamic benefit. Air flows over the structure and tapers off at the back, similar to the shape of a teardrop. The vehicle is also lighter, requiring less energy to move it. It hence can be emulated in our task as it is feasible and cheap. Such designs are increasingly used in the automobile industry, as an alternative to a 2-wheeler motorcycle and a standard 4-wheeler car, due to its fuel saving ability and its proficient handling.
5.3 Evaluation of engineering goals
Our vehicle was able to move at an average of 5.93m after modification. This meets the engineering goal of being able to travel a minimum of 5m with an egg. Our vehicle has an egg-holder fitted onto its back for transport of an egg.
5.4 Areas for improvement
We have observed that the car tends to curve towards the right sometime after the lever has fully released. This was caused by one of the back wheels not aligned perpendicularly to the ground, causing the car to veer off course while coasting. This can be prevented by marking out on the axle where the wheel should be positioned. We can also fixed a cable tie onto the axle before attaching the wheel. The cable tie serves as a permanent marker after tightening, so as ensure the wheel is aligned correctly.
We are currently using a circular axle as a drive axle. It is better to use a hexagonal one, similar to a pencil shaft. It enables the string to wrap around the axle tighter, hence each rotation has little energy wasted. We have to pull the string tightly around a circular axle now, which is not efficient. If the drive axle is hexagonal, there would be a need to fit bushings onto the areas in contact with the chassis. The bushings can be made out of recycled correction tape parts and serve to cover the hexagonal edges of the axle. This allows a circular area to be in contact with the chassis, reducing friction.
5.5 Practical Applications
The components of the mousetrap car can be compared to real life examples. Designers would want a chassis and frame to be aerodynamic and lightweight, to be able to save fuel. Reducing friction at certain points of the car is key to making it travel further. Industrial applications such as applying lubricants to axles and gearing enable the vehicle to be more fuel efficient.
5.6 Areas for further study
We can investigate differences between a 3-wheeler (teardrop-shaped) and a 4-wheeler vehicle. Due to advantages such as being lightweight and aerodynamic, it is feasible to compare with our current vehicle and to establish which of the two is a better design. We can also investigate whether using two strings, each attached to the left and right of the drive axle (area between wheel and chassis) can affect its performance in terms of speed and distance travelled.
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