Custom 3D Printed Carbon Fiber Bike Frame

Step 13: The Rest of the Joints

It is completely possible to do the rest of the joints the same way as you did the dropouts, laying up your carbon fiber and then using a compression-wrap to compact the joint. However, many of the joints on a bike are much more complicated, with multiple tubes meeting at the junction, complicating the wrap. Generous fillets will help, but if you use this method, you are probably best off using unidirectional carbon fiber only on flatter, smoother transitions to prevent bunching. Woven cloth (especially ‘twill’ and ‘satin weaves’) conform to compound curves much better and will help you get a superior part both cosmetically and structurally.

One disadvantage of the hand layup / compression wrap method is that it tends to be fairly labour intensive. It is more difficult to achieve a uniform wall thickness of carbon on your part, and there will almost always be a fair bit of sanding required to get a good finish. Sanding carbon fiber is a pain, and also breaks the long strand fibers that make the part strong.

I wanted to take full advantage of 3D printing technology for this project, and decided that I would create 2-part female moulds to complement the male “core” sockets that were used to jig the frame together in the first step. I could then lay my carbon fiber into the moulds and clamp them over the joint in order to get a compacted, uniform joint which would require less difficult post-mould finishing.