Carbon Fiber Bike

I AM NOT A PROFESSIONAL FRAME BUILDER , this is my first bike build.
BUILD AND RIDE AT YOUR OWN RISK




I am, however, a student in Polymer and Fiber Engineering at Auburn University with access to a composites lab. We have all sorts of fabrics including carbon fiber, fiber glass, kevlar, and all of those in prepreg as well. I got interested in biking from my dad and have always loved to make things. I found a couple instructables on bamboo bikes and decided i would make something similar. I figured I could make a carbon fiber bike if I replaced the bamboo tubes with carbon ones. After a couple failed attempts I made some decent tubes, it really isn't that hard.

Completing the bike has taken about 4 months, but i could make one in three weeks if i were to spend a lot more time on it. I decided to make a fixed gear because of its simplicity. I don't have to worry about a rear brake bridge, clamping the front derailleur on the seat tube, and all of the cable stops. Plus I already have a geared bike.

I didnt know much about composites or bike building when i started this project, but I know a lot more about both now. Having an experienced frame builder also helped a lot. Having a lot of contacts for tools or advice is a must for this.

I encourage anyone who attempts this project to do a lot of research before hand, I did for about 2 months and asked lots of questions to anyone who knew anything about bikes. I used Sheldon brown's website a bunch for info. They have a bunch of singlespeed and fixedgear stuff as well as basically anything to do with bikes.

Some useful sites:
http://www.bikeforums.net/showthread.php/596392-Bambooo!?daysprune=-1
http://www.instructables.com/id/How-to-Build-a-Bamboo-Bicycle/
http://www.instructables.com/id/How-I-built-a-carbon-bike-frame-at-home-and-a-bam/
http://www.instructables.com/id/Bamboo-Bike-2/
http://www.instructables.com/id/Bamboo-and-Hemp-Road-Bike/
http://www.bikeforums.net/showthread.php/659162-Bamboo-frame-Worklog-MADE-IN-BRASIL?daysprune=-1
http://www.instructables.com/id/The-simplest-bicycle-framebuilding-jig-I-could-com/


There are two things that you will learn aside from dealing with composites and building bikes; patience and the hatred of sanding.

This is not a project for everyone and not a project you can do in a weekend.

Oh yeah, DON'T GET YOUR BOTTOM BRACKET SHELL BACKWARDS LIKE I DID!

Step 1 Making the Jig

You need:
2x4s (scrap will do)
3 "L" brackets (I think 5 inch long)
3 feet of threaded rod (I used M10 x 1.5)
3 cone shapes that fit into the head tube and seat tube
I used a pvc mandrel to hold the bottom bracket shell
6 lock nuts (for rear drop out assembly)
4 regular nuts (for head tube and seat tube assemblies)
6 washers (for rear drop out assembly)

There are 3 vertical 2x4s that hold the head tube, seat tube, bottom bracket, and dropouts. There is a second piece of 2x4 on the back of where the bottom bracket hole goes and where the rear dropout hole goes. I got the measurements from an old bike frame. the cones were made on a lathe out of aluminum stock, I threaded a hole in them so i wouldn't have to use more lock nuts. I drilled a hole for the bottom bracket shell mandrel with a hole saw ( you need a tight fit so it wont move), the pvc was turned down from 1.5 inch so that the bottom bracket just fit. The droputs fit nicely onto the M10 rod. I drilled a hole through the 2x4s for the rod and put a washer and lock nut on both sides. the dropouts are secured with a washer and lock nut on each side. If i continue to make bikes I'll upgrade the jig to extruded aluminum, that way I can make different sizes.

Comments

[frisbeechamp1983]

Could this be used to make a hardtail frame?

[Pankake]

The jig would look a lot different. Your downtube would need to be moved to accommodate the wheel traveling with the suspension.

[frisbeechamp1983]

Could you use a Carbon fiber kevlar blend?

[Pankake]

Possibly. I don't think any company uses kevlar in their bikes. Kevlar is not as stiff as carbon fiber which would translate to your bike.

[SIMSHI]

great instructable, thanks so much. I was wondering if you could tell me where you sourced your cone shapes from. I'm building a jig for bamboo frame building and am having some trouble finding something suitable that isn't a trailer hitch ball cut in half.

[Pankake]

The cones were turned on a lathe. I went through the same process of trying to find something similar but had no luck. I hope you can find something or have something made.

[james_kim2]

Oh and I also might add,

Installing the Drive arm on left side makes no difference in unthreading of the BB.

As you might have mentioned its the bearing that puts counter spin on the torque applied to the shell that unscrews the BB flipping the side of drive would make no difference. (In fact as you've experience it creates additional problem of having your pedal come loose)

In reality, tightening the BB super ***ing tight (40nm is a lot more torque than most people realize) and bit of Red locktite or similar threadlocker and you might not even have to use the YST threadless BB. (For example, Italian BB with 70mm shell width has right hand thread on both side of the shells. So the driveside would come loose if you don't torque it properly.) Oh, don't forget to check the torque every once in a while.

[Pankake]

I am thinking about making another bike with an integrated headset, maybe derailleurs, try to make it lighter...or cutting the bottom bracket out of the current one and turning it around, then wrapping the joint again. You can do that with composites which is pretty cool.

[james_kim2]

Hello Pankake.

I have really enjoyed reading your post!

I suggest you use YST threadless B.B (They stopped making this couple of years ago but last batch is still going around so ask around your local bike shop) with plenty of Grey Locktite for press fitting.

Hope this helps!

[Honus]

Awesome job! Regarding your backwards BB shell- one thing you could do is find an older Mavic cartridge BB (assuming your cranks have a square taper) as it is a whole assembly that slides into the BB shell and is held in place by tapered rings on each side- the BB shell threads aren't used. I even have the special tool kit to install it and cut the tapers- I'd be happy to loan it to you.

[camp6ell]

velo-orange makes a threadless bottom bracket that would work too:
http://store.velo-orange.com/index.php/components/bottom-brackets/grand-cru-threadless-bottom-brackets.html

[palms14]

hey have you ever thought of just using pre fabricated sheets? what are your thoughts on those?

[Pankake]

Do you mean Prepreg, as in pre-impregnated with resin? I wish i could think of a simple way to use it. The problem comes in when you have to bake it. The prepreg needs to be cured at a high temperature, say greater than 200 F. I might be able to use a prepreg with low temperature cure resin in my pvc tube jig, then take it out of the jig and do a post cure at a higher temperature. But I am concerned that ,when i wrap it then heat it up to cure, the layers wont slide over each other to expand inside the tube. Wrapping the fabric on the outside of a mandrel is tough because you have to then get the mandrel out. Any good composite needs compaction to be strong and its hard to do that by wrapping around a mandrel then getting a mandrel out. The other way to use those is in a two piece mold with a silicon bladder which can get very expensive.

Is this what you are talking about?

[palms14]

here is a link... couldnt you just wrap the sheets around a tube?

[Pankake]

I don't see any link there. Could you try posting the link again?

[palms14]

So sorry bout that bro here you go http://www.carbonmods.co.uk/Departments/carbon-fiber-kits.aspx

[Pankake]

All of those kits look like dry fabric and resin, which is what i used. If you wrap it around a tube it is hard to get a good finish because you cant get the slack out of the fabric. plus you cant get the tube out.

[palms14]

dude thanks so much your awesome.

[TSC]

I think this is the best enter instructable in the bike constest so far!

[ltnemo2000]

How stiff did this turn out? Can you feel the road or is it more mushy? I, personally, love the left-side drive. even if it was a mistake and totally impractical, it's really cool. what kinds of carbon did you use where? I'd totally make a time trial bike this way. thank you very much for posting.
>G

[Pankake]

The frame stiffness is great. I can feel the road but it isn't jarring.
I used a regular twill for the down tube and the top tube. for the seat tube I used a unidirectional for two layers then a twill for two layers. I will eventually post a video or more steps on the making of the tubes. The stays are a wooden dowel wrapped with unidirectional fabric (the fibers are parallel to the dowel) then vectran braided over that to compress it.

[Z.Backas]

This instructable has definitely placed building a carbon fiber bike back on my to-do list! Thanks!
What do you think the total cost for parts was?

[Pankake]

The epoxy resin is from US Composites. I have a picture you can get some info off of in the instructable. I used maybe a gallon of the stuff so i would get a gallon of the resin and 1/3 gallon of the hardener. About $70.

The fabric will cost you a couple hundred. It looks like you can get fabric from US Composites, they have a discount section on their homepage. If you dont mess up on the tubes you will probably use 5 yards of a 30 inch wide fabric. But I scrapped a couple tubes on my first tries. You also need tow. Its like a yarn of carbon fibers. I read on some instructables that they got this stuff from ebay?

I didn't get cheap parts stuff because I plan to use most of it for a long time
All of the parts on the bike cost about $500. I basically got new everything. The only things that weren't bought on the bike are seat, handlebar, stem, and pedals. you can definitely go a lot cheaper. Look for stuff on craigslist or ebay or in your local bike shop.

[notingkool]

exelent frame, i like it. And the left side chain is a good detail.

[SyntheticChelovjek]

I like your tutorial! I think it's great that you tried your hand with advanced composites, and the results don't look bad at all. I'm currently going to school for composites and a friend of mine is also building a bike frame. If you plan on doing it again, I'd recommend experimenting with Partall wax (it's a PVA mold release designed to help you release composite lay-ups from their tools, and improves surface finish). In my lay-up experiences, that has made life much easier.
My friend is a machinist and built aluminum molds for his frame. He also made silicone bladders to inflate on the inside to compress fabric together which can easily handle 60 psi. The parts are molded separately, but each part incorporates the joints into them so that they don't need to spend time locating them later. Maybe try building a re-usable PVC mold that incorporates the joints. If you cut and pieced together a PVC frame (where the inside diameter was your final outside carbon dimension) in the same way that you put together the carbon bike frame, you'd essentially have a PVC bike. From there, you could cut it at locations that were better for bonding the carbon later, and create molds from the other pieces. I realize you'd be unable to remove parts from molds with angles in them, so you'd have to cut the molds to make a parting line where you could remove the final part. This way, you'll have control over your fiber orientations at the joints and where there are discontinuities in the frame. Good luck!

[Phil B]

Thank you for all of the details on your project. It looks like a lot of work. I would say you earned all that you saved by making it yourself. If it were not a fixie, would you have needed to add lugs and fittings for cables, a rear brake, water bottle lugs, etc.?

[Pankake]

Yes, that is why I made a fixed gear for my first attempt.