Lost Lemonade Bonded Frame
Building on techniques from previous projects such as the LP29 Downhill Bike and the Bond vs. Weld Test, I set out to design and manufacture a bike frame entirely from CNC-machined components that were bonded together instead of welded. This approach aimed to combine the precision and design freedoms afforded by CNC machining with the durability and simplicity advantages of adhesive bonding to create a novel, high-performance frame.
Project Definition
The goal was to develop a fully functional bicycle frame using adhesive bonding between CNC-machined components, eliminating the need for traditional welding. The project required optimizing adhesive joint design, machined component size and shape, and bonding jig and alignment techniques to ensure durability and performance comparable-or superior-to welded frames. Key challenges included achieving precision alignment of components, ensuring strong and reliable bonds, and verifying the frame's mechanical properties under real-world loads.
Project Design
The frame was constructed from individually machined components, designed for self-aligning, high-strength adhesive joints. Inspired by motorsport and aerospace bonding techniques, I incorporated tapered lap joints to maximize bonding surface area while maintaining structural integrity. Shape optimization was used to identify critical load-bearing areas and reduce weight were applicable. To simplify assembly and improve consistency, I designed 3D-printed jigs for positioning components before bonding.
An unexpected failure occurred in the first prototype due to a stress riser and an unforeseen load type. This highlighted the necessity of real-world testing and an expedited design cycle to identify and address unforeseen problems. To address this particular failure I quickly iterated on the initial design by adding a material bridge to prevent deflection, and incorporating a larger fillet to reduce the stress concentration.
Project Delivery
The completed frame successfully demonstrated the feasibility of a CNC-machined, bonded bicycle. The bonding process resulted in an expedited development cycle and improved design freedom when compared to traditionally welded frames. This project not only validated bonded frame construction but also opened doors for future modular designs with manufacturing flexibility.
