Yes the full front triangle was done in printed negative moulds, including the top and down tube. It was a good exercise and I learnt a lot, but if I’d do it again I would probably make a quick negative mould on printed plugs and work with prepregs instead. It’s just so much more convenient to work with.
The chain slap protector is cast from a soft PU casting resin in a 3D printed mould. I’ve done the same thing for my last bike and this works extremely well. I was considering printing directly in TPU, but do not like the shine, and the PU I chose is a lot softer (it’s 50 shore A now). Printing with supports in TPU is also not easy.
Got to ride it for the first time properly on trails. Everything feels really solid and the whole ride was uneventful - just how we like it for a first outing.
Geometry feels really dialed for me for a trail bike. Compared to the enduro I went with a slightly longer stem, shorter reach and slacker seat tube angle, which feels much more appropriate on flatter trails.
Light wheels and short travel definitely is fun, and i enjoyed it much more than i thought i would (i usually ride longer travel bikes)…
The shine on the printed TPU goes away in use when subjected to abuse of drivetrain. I have printed a few STUF chain tamers and they come out shiny but after a but of riding they end up dull and matte.
I keep coming back and admiring this build. So good. When you bonded the tubes to the dropouts, did you use a different resin than in your main triangle layup? Did you make or buy the tubes for your rear triangle?
All tubes ar made by myself, but the rear triangle was made in machined aluminum tooling from prepreg in the autoclave. So different process, mostly because that’s just the best way to do it and the tubes are small enough to just machine them from aluminum on my CNC router.
Oh nice, I didn’t realize the rear triangle tubes were aluminum. I don’t know enough about composites to know if this is a dumb question, but could you bond an off the shelf carbon tube to a forged carbon component like a dropout or some other junction and maintain strength?
No the tubes are carbon, just made in aluminum moulds. Sorry for my convoluted response
Technically yes, you can bond a forged part to a carbon tube or an aluminum tube and have a very structurally sound thing. However, with bonding it’s very easy to mess things up and you will have something that looks good visually but is 5 times weaker than theoretical or has poor fatigue life.
Happy to answer any specific questions. A lot of it starts with the design already.
Thanks for the info! It looks like a single lap connection. Is there a rule you use for how deep you make the overlap? Like 1x(tube diameter) or something?
That’s already a complex question. I’d say if you have the same material on both sides of a single lap joint, the longer the better, but anything after like 25mm length is going to have diminishing returns.
However, this highly depends on the bending stiffness of you laminate, if and how it’s tapered and, …
And if you have dissimilar materials you might run into scenarios where shorter is better due to shear stresses due to thermal expansion. I had some good research papers i can dig out of you want (I’d need to check what i can share and what i can’t)
