As of recently I spent too much time thinking about how a composite frame would actually be easier to build at home for most people, compared to a steel bike.
The fixture table can be a flat sheet of MDF with a bunch of 3D printed brackets, no weld distortion, tubes can easily be shaped with a file and a dremel, most expensive tool that is really required is a vacuum pump, and ideally a curing oven, but as the temperature requirements are low, there are easy ways to make something. Heck - I cured my first frame in a decommissioned freezer, that i heated with with a bunch of incandescent light bulbs.
I think the biggest hurdles are a lack of information, and availability of nice tube sets. With this forum we can easily solve the first point. And to address the second I was thinking about designing a nice tube set myself.
Started on a parametric design for a gravel/road bike in CAD. This is where I’m at right now:
tubeset with forged dropouts and upper seat stay to seat tube connector-thingy
UDH hanger
flat mount brake interface
Lower headset can accommodate 1 1/8" integral or 1.5" traditional cups, and would match the diameter of the crown on a futura gravel fork
PF30 bb
What is your opinion? Any interest? What would you like to change? What standards would you build it around (seat tube diameter? cable routing? tire width and clearance? Bottom bracket standard?
I think what would unlock Carbon for the people would be a low cost pre-fabbed chainstay subassembly, just as you designed: BB > CS > Flat mounts > dropouts.
The BB-CS subassembly requires the most strength and has the most complexity. The front triangle and the SS’s are much easier.
If the raw materials cost for a carbon frame is <$1000 and the tooling <$300, it could be a reasonable hobby and weekend project.
The challenge I see is who would be willing to put up the cash to invest in carbon molds and sub-assemblies for the DIY hobby market? Right now there is no economy for it, and the custom carbon builders have their own tooling and designs.
Tube-to-tube or lugged carbon can be super easy, but as Brad said the barrier is knowledge. Check out Easy Composites on youtube, they have some amazing how-to videos. They also sell a range of beginner and more advanced kits for various general projects (many of which can apply directly to making a carbon bike frame) as well as all manner of commercial-grade composite materials and tools (UK-based but they have warehousing in the EU and China for worldwide distribution). There’s even a 40 minute film of them making a monocoque, split-moulded DH bike (a bit beyond the average DIYer but by no means impossible).
I think that a pre-made or modular chainstay/dropout system would be the most beneficial and versatile product to bring to market - rather than an entire frame kit. This gives an easy option for the most complex components, but still allows a lot of freedom for design and spec choices. Following that, in order of complexity/necessity for home builders, I’d go for BBs, headtubes, seatstays, seattubes then main tubes last.
I agree that it can be the lowest barrier to entry process. My 1st carbon frame was done with foam mold cores and compression wrapping. All done with room temperature curing epoxy. It was 10 years ago, but I had less than $300 in materials in that frame and fixturing. Thankfully now there is a ton more info available about the process of making carbon parts.
I’m in! Never done carbon, played with a bunch of fiberglass and liked it a whole lot. I’d like a steel front end with a carbon rear. The foam mold cores sound super interesting, I’d like to carve a foam rear end and wrap it all Looking forward to seeing smarter people than me work on this.
I know Vlad in that EasyComposites video and he now works for We Are One making the Arrival frame. He came over this spring and we stuck a dropper length seat tube onto a DH bike. He’s the carbon whisperer!
That’s very cool! I was almost out of things to stay awake at night pondering, this will help.
Funny, I met a guy named Vlad who was riding a We Are One Arrival frame at Angel Fire this last weekend. Not that one, but seemed too good a coincidence to not mention. That seat tube surgery is cool as hell! Cutting stuff up makes me smile every time.
For anyone looking to make complex tubes (eg chainstays), have a think about 3D printing a dissolvable mandrel to wrap your carbon over. You can get water-soluble PVA filament which should hold up to an epoxy laminating resin (you can get PVA mould release agents and I haven’t found any evidence that epoxy will attack or stick to the PVA filament). Or I think you can use more conventional PLA or ABS and dissolve them with acetone. You only need a conventional wet lay-up with compression tape or a vac bag for consolidation. Potentially you could use prepreg but only if the working temp of the filament is above the cure temp of the carbon.
This has been in my head for days now. I have a front triangle all tacked up, just waiting for its butt end and I can’t stop thinking about trying to make a cabron fiber (that’s the spelling I’ll be using from here on out) rear triangle. I don’t cad and I don’t 3d print, so I’m considering trying to carve it out of foam and wrap it. It’s pretty small, so I could probably bag it without too much trouble.
I’m willing to pull the trigger on it if. We could do a whole walk through here or make a youtube that nobody will watch? I’ll put my little bit of money where my incredibly big mouth is and try it if there’s any interest. Shit, I’ll probably do it anyway.
I’ve done parts with dissolvable foam cores, PVA cores, ABS cores, and wax cores. I’d love to show more about it all but I’m struggling with spare time at the moment! Best of luck with your projects.
I don’t think acetone dissolves PLA but on another forum there’s a chap making car parts by wrapping PLA prints in carbon and dissolving it with d-limonene
Edit: just checked, he’s using HIPS filament not PLA so I’m probably wrong about the acetone
Thanks for all the feedback everyone. I had a bit of a crazy week but I am excited to continue the project as it seems there is some interest. I’ll probably start machining some moulds for a set of chain stays and see where we go from there. I am not disinusional and planing on any sort of big business, especially being located in a high labor cost country. Clearly just a passion project.
I built my road bike around printed cores, but used vacuum infusion instead of hand laminating. I used some PLA cores that were removed, and some ABS cores that were dissolved. Vacuum infusion certainly works, but there are also limitations, especially if you plan on using prepregs to wrap the joints. The glass transition temperature of most infusion resins is getting pretty close to the curing temp of prepreg resins.
wrapping foam cores works as well, but it can get tricky as a vacuum bag easily deforms the core to a point where it is not usable anymore. I worked around that in the past by hand laminating a first layer onto the core, letting this cure and then continue in vacuum infusion for consecutive layers.
@SoyWater I am not sure those dropouts are particularly well suited to be bonded to carbon (sorry, I meant cabron). I’d be excited to help out tho in any way with some 3D modeling or whatever it might be. even machining some foam cores or whatnot. We’d just have to figure out shipping overseas i guess…
Hi. My chainstay was maked by the same process. First I create core from blue foam and laminated by one layer of fiberglass (but continue with wet hand laminating). After curing I start to put carbon layers but as I do not have vacuum…I use nylon tape for some press.
Exists foam which could survive 120 degree of celsius? Because we can use prepreg by this way:
Looking forward to seeing smarter people than me work on this.
