I used to work at Lotus Cars, bonding fibreglass components (specifically the front crash structure, so a fairly critical part). Not only did we work in a small self-contained room within the factory - to keep dust out and for fume extraction - but the prep for each bond was about 95% of the work. Clean with acetone and scotchbrite, wipe down, 2 coats of primer, then adhesive; it was a very specific process with a whole binder of ISO-accredited instructions. Still one of my favourite jobs ever, even though I never got to drive any of the cars…
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Here’s a fun little post that’s worth checking out. Look at those svelte titanium lugs!!
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And that little carbon fibre rear light!
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I have been thinking about how to do this a lot recently. I know for road frames you can get away with FDM printed lugs as long as you use CF nylon. I don’t know how strong it would be, but I have seen it done once.
I like that process July uses, and they look incredibly clean for being lugged.
The idea for the process I have been toying with of late is using forged carbon lugs. On paper, they should provide the strength needed if built right, and forged carbon looks much easier then carbon sheet layup for small parts like that.
I am probably missing something with this process, and realistically should just use aluminum as my end goal is an enduro bike, but I have been thinking about the process far too much to stop now.
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Never heard of using 3D printed plastic lugs, might have to give that a look. I would imagine you’d need to fully wrap the tube and lug to give enough strength. Forged carbon can be a great way to make really strong irregularly shaped parts, though I don’t know if it would be any easier for a lug than using a conventional lay-up method (and would likely be a bit heaver than lay-up too).
Check out Easy Composites for some great how-to videos on all sorts of topics. They have a few vids on forged carbon and even a couple of 3D printed carbon and mould-making.
A lugged bike can never be as light as a traditional layup. However, on paper, they are stronger. I do still wonder if doing forged carbon would work or not, but I am also starting to question the complexity of home made lugged bikes. Either way, excited to see what people can do!
I am very familiar with Easy Composites, great videos!