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Custom 3D Printed Carbon Fiber Bike Frame

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If you’re really into cycling and are on this site, chances are that over the years you’ve at least toyed with the idea of making your own frame. There’s something truly special and deeply rewarding about riding something that you’ve built yourself, and being able to choose whatever custom geometry and extras that you want only adds to the appeal.

At that point you probably looked at everything that you needed to do to make a bike. And that’s when things start to get daunting. Before you’ve even thought of the bike, you need to think about the jig. Fabricating a jig with basic versatility and functionality for framebuilding takes time and patience, and the raw materials costs are at least $200 [Instructable example!]. Rapid-prototyping has pushed the costs of pre-made bike jigs from $1000s down to $300 or so [such as the Jiggernaut], but if you don’t know how many frames you really want to make, it’s still money that you aren’t putting towards your first frame.

Next, you need to consider the tools that are specific to typical framebuilding. If you want to learn to braze steel frames, an oxy-acetylene starter kit with everything you need to get brazing is something over $200 (plus the price of an additional gas cylinders, brazing rods, and flux that you’ll use). A TIG welder suitable for working with thin-walled steel and aluminum bicycle tubing is more like $1000.

Next, the materials for the bicycle frame itself. While it would be possible to braze a frame with commodity straight-gauge 4130 (chromoly) steel tubing, it would be very heavy and wouldn’t ride very well - bike specific tubesets are double- or triple-butted to save weight and place extra material at the lug junctions. Bicycle specific tubesets will cost you upwards of $100, and a set of lugs and dropouts is about another $100.

If you’ve been adding up the tally, you’re already at more than $600 for your first frame – hopefully you won’t make any mistakes!

I wanted to design a process for building bicycles that allowed an enthusiast to spend less overhead, less time on finicky details, and put the emphasis on actually designing and making a bike that you want to ride.
 
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lonestarnot10 days ago

I'm south of DC, wondering how to assemble a group to do several bikes together, maybe at a local maker space. Beyond this FANTASTIC Instructable, what would you suggest for organizing such a group effort?

ovasilyuk2 months ago
http://d4d.ucoz.ru/
ovasilyuk2 months ago
http://d4d.ucoz.ru/
albatrill7 months ago
This is amazing, truly, thank you for the time you spent making and documenting this.

I am interested learning more about 3d printed molds and carbon fiber, can you please recommend some books or websites for various Carbon Fibers, resins, processes and theory?
This definitely needs to go in the Bike Contest.
Toulouse1 year ago
This is a very nice writeup. I'll be experimenting soon with something like this -- your instructable has been quite inspirational, thanks!
brchase1 year ago
Very nice job and explanation. You obviously spent a lot of time documenting your progress.

Question: Did you think about using carbon fiber tubing in lieu of the aluminum, There appears to be tubing built and sold for bicycle from Rock West composites(http://www.rockwestcomposites.com/)?

I have used some of their tubing for small parts of a DIY handcycle.
Hi Androole,

I just joined instructables so I could thank you for taking the time to post this, the way you set out the info and your detail is amazing. Also, an awesome idea I had pondered before, but you well and truly beat me to it!

How is the bike holding up?
rodjava1 year ago
Hi,
I can't thank you enough for sharing your build. In particular, the 3d printing aspects. It's a perfect way for home builder to build the bike of their dreams.
Fantastic! Thank you, Thank you, Thank you.

Rod
San Francisco
I'm extremely impressed and sold. Couple of questions -

Are there any 3d printing services you would suggest for a project like this?

What type of material is the print made of and how strong is it?

And just to clarify...are you using the actual print for the lug and then wrapping additional carbon fiber around it - or are you just using the print to make 2 part molds with which you then make carbon fiber lugs? (I wasn't exactly clear on this)

Amazing work and thanks!
Androole (author)  squishacorn1 year ago
Thanks for the kind words!

As far as 3D printing materials and services go, I used ABS plastic printed using the Fused Deposition Modelling (FDM) style process. This was popularized by manufacturers like Stratasys and Dimension. It's also the process used by just about every inexpensive desktop/DIY 3D printer. It's cheap, and the parts are quite rigid and reasonably tough. The compound curvature and smooth transitions of the lugs also makes them quite strong. The detail is not as good (you get a bit of the 'stair-step' effect), but that's not as important here.

Most 3D printing services now are using Selective Laser Sintering (SLS) nylon/polyamide because it's relatively cheap, produces great detail, and the parts are very durable because they are flexible. The downside to that flexibility is that unless you use a high wall thickness on your parts (read: expensive, heavier) you lose the dimensional accuracy that you need to make this work.

As services go, Shapeways no longer does ABS, but Ponoko has it and calls it Durable Gloss Plastic (http://www.ponoko.com/make-and-sell/show-material/348-3d-printed-durable-gloss-plastic-black). You might be able to get away with Shapeways Alumide, but I'd be concerned that it's too brittle and not very forgiving. There are loads of other rapid prototyping services out there, but I can't vouch for their pricing or user friendliness.

As far as the moulding process, the answer to both of your questions is "yes." I printed the actual lug that defined the geometry of the tubing, but also printed 2-part moulds to compress the carbon fiber around the lug mould. This means that the plastic 3d-printed parts are still inside the frame, but they don't weigh much, and I figure it can't hurt to have a little bit of impact resistance (especially given that this is a prototype process).

Hope that helped!
jstoner1 year ago
Dang. Just... dang. Love it. Forwarding to my bikey friends.

I've wondered for a while: is there any merit to the idea of using 3D printing to deposit carbon fiber directiy? Usually you're printing with a filament anyway. I imagine someone has to have tried that.

It would be a pretty different print head, adding epoxy as you laid down the fiber instead of heating. You'd probably have to take it into account in the path the print head would take. And you'd probably have to print a negative to do needed compression, like you did here.

Also, did your front wheel hit the pedals?
The technology you're looking for is called filament-wound carbon. It's generally restricted to making carbon tubes and tanks, but it can be used (with 6+ axis machines,) to make more complicated things.
Here's a company that uses an unusual winding technique to make bikes.
http://www.delta7bikes.com/delta7-bikes.htm

I know I saw at one point a bike frame maker that used a single carbon strand to make an entire frame out of, but couldn't find it.
Androole (author)  jstoner1 year ago
I've heard that idea of 3d-printed CF filament before. It's very interesting, and could lead to some absolutely incredible properties by optimizing the fiber direction and making it continuous, but as you say, it would need some pretty significant custom design work. Epoxy obviously has a short pot-life, so you'd need some system to automatically meter and mix new resin and purge the old stuff, and the path of the print head is clearly vital to the engineering properties of the part.

One option would be through the use of a dual-nozzle printer with carbon fiber and a thermoplastic composite rather than thermosetting (i.e carbon-fiber reinforced ABS rather than epoxy). You'd likely need to reheat and compress the final part in a mould, as you say, to get the plastic matrix to encapsulate the CF properly, but you'd potentially have a pretty amazing, absolutely customized finished part with much better impact resistance than a standard epoxy part.

...and finally, yes, there is a little bit of toe overlap during tight cornering due to the geometry. The pedals don't touch, but the tips of your feet can at times. I had the wheelset lying around so I used it, but this could be alleviated by using a suspension-corrected 26" fork (to keep the overall axle-to-crown offset the same) and a 26" front wheel to reduce the diameter.
jdetlefsen1 year ago
interesting, with a bit more work you could make reusable molds and produce those bikes in a small series, or am i wrong?
Androole (author)  jdetlefsen1 year ago
You certainly could! With some stronger moulds (read: thicker plastic wall thikcness), somewhat more care taken during the prep process (better buffing & polishing of the mould release wax, and better mould release compound) I think it would definitely be possible to make reusable moulds for small batch production. They wouldn't last many pulls, but certainly more than one.
espdp21 year ago
Uhhh...WOW! That is sweeet. Can you post a short video of you riding it around, please? I want to see it in action.
Androole (author)  espdp21 year ago
Thanks! I overstrained my knee a bit as a ride-along mechanic for a 220km charity ride this past weekend, but I'll see how I'm feeling and try and get a video posted in the next week or so.
jastilix1 year ago
Very nice writeup - 2 questions : how did you calculate if adequate force for vbrake bosses under max limits, how was the frame alignment after finishing, and frame weight?
Androole (author)  jastilix1 year ago
As far as the V-brake stresses, I looked more at precedent than doing all e the calculations from scratch. While the ultimate tensile strength of epoxy is obviously far lower than aluminum (about 1/6), the epoxy bond area covers the entire backside of the brake boss tube, whereas the weld area is only around the periphery of the joint. So the overall joint strength should be approximately equivalent. The carbon fiber wrapping was then for insurance, and this is one of the few instances where I wrapped the fibers circumferentially, giving the addition hoop strength to resist the braking forces. On top of all this, the rear brakes only contribute about 30% of the overall braking force on a bicycle due to weight transfer, so their loading is significantly less than the front brakes.

Frame alignment post-finishing was spot on, to the best of my measuring abilities - as soon as all the 3d-printed joints are glued into place in the early steps, there's very little opportunity for the frame to shift during moulding.

The frame weight disappointed me a little bit - it was about 2300g. Given the unusual geometry and the sheer amount of tubing (call it an XXXL frame) and the frame's stiffness, that actually isn't terrible, about the same as a nicely built 4130 chromoly frame. This frame also has a thick MTB headtube, BB shell, and dropouts that I'd salvaged, which are not very lightweight. For this iteration, ultimate weight reduction was not my priority, so much as to make a more accessible way for people to build custom-geometry bikes. In my next version of this frame, I may experiment with vacuum-moulding the 3d-printed lugs, which will allow me to significantly reduce the amount of resin in my moulds. I expect that dropping 300-500g of weight would be very easy, and even more would be possible with some care and optimization.
bmwer1 year ago
Very cool project!

However, I'm curious about the proportions/geometry? The seat post seems much too angled so that raising the seat actually means pushing it further back making it harder to reach the handles. Was this intentional? I'm just curious what the benefit of this geometry is? It doesn't look like any bikes I've seen before.
anglo bmwer1 year ago
@bmwer

google for "RAN" bicycles, This biks is modeled on that form.
Androole (author)  bmwer1 year ago
The bike is basically a semi-recumbent - it marries some of the reclined comfort and efficient pedalling of a recumbent with the more conventional handling and packaging of a standard diamond frame. It takes a little bit of getting used to, but it's fun, and totally different. At some point I plan on building myself a moulded carbon seat, possibly with an integral lumbar support.

You are correct that pushing out the seatpost increases your reach to both the pedals and bars - it's actually an advantage when it comes to accommodating different sized people. Me and four of my friends ranging from about 5'5" to 6'1" rode the bike in one session and all of them were actually okay - try doing that on a regular frame!
ben_k1 year ago
The carbon lugs look great, especially with the gussets you incorporated into them. I wish I'd been able to make them as nice on my bamboo bike.

With the ... unusual... geometry you chose, I would be worried a bit about the seatpost, if it's carbon fiber ( I can't tell from the pictures, but it looks like it might be). They really aren't designed to have as much side load as yours will, because usually the seatpost is much closer to perpendicular to the ground.
Androole (author)  ben_k1 year ago
Good call on your concern - it's actually a rather beefy 31.6 aluminum Race Face Evolve Downhill seatpost - I needed it for its special 360 degree clamp that could hold my seat at such an extreme angle.
omnibot1 year ago
Wow!!! That is awesome. I love how the printed lugs become intergrated. This takes 3d-printing to a whole new level since this would be possible with a homemade reprap.
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