Analysis Context
Tandem bicycles, designed for two riders, present unique challenges in terms of design and performance. They require a robust and lightweight frame to ensure optimal performance and durability. The report focuses on designing such a frame that not only meets the size constraints but also achieves a high resonant frequency and long lifespan. These factors are crucial in ensuring the bicycle’s performance and the comfort of the riders. The study assumes ideal conditions, including perfect joints and no material damage due to external effects. While these assumptions may not hold in real-world scenarios, they provide a baseline for understanding the performance of the frame under optimal conditions.
Methodology
The design process for the lightweight tandem bicycle frame began with the lightest frame possible, with an average wall thickness for aluminium bike tubing around 0.8 - 1mm and an average diameter of the tubes around 38mm. These dimensions were chosen to minimize the weight of the frame while ensuring its structural integrity. The second iteration of the design aimed to increase the resonant frequency by 20% compared to the initial design. This was done by adjusting the dimensions and geometry of the frame.
The study assumes ideal conditions, including perfect joints and no material damage due to external effects. While these assumptions may not hold in real-world scenarios, they provide a baseline for understanding the performance of the frame under optimal conditions. The boundary conditions for the simulations were set to mimic real-world conditions as closely as possible. The frame was fixed at the points where it would connect to the wheels, and the loads were applied at the points where the riders would be exerting force. The magnitude of the loads was based on the weight and force exerted by an average rider.
A fatigue simulation was conducted to evaluate the lifespan of the frame. The frame was subjected to 1 million loading cycles, which is equivalent to 10 years of use. The simulation provided insights into how the frame would perform over time and under various loading conditions. The frequency simulation was conducted to evaluate the resonant frequency of the frame. The goal was to design a frame that could withstand a natural resonant frequency of over 30Hz. This frequency is significant as it ensures the frame will not resonate with the pedalling frequency of the riders, thus providing a smoother ride.