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Step 3: Making the Tubes

You need:
carbon fiber fabric (I used a light twill fabric and some unidirectional fabric as well)
peel ply (resin wont stick to it)
epoxy resin
fiberglass fabric for metal tubes.
3 ft of pvc tube ( here the inside diameter will determine how big your tubes are)
2 pvc end caps
10 or so pipe clamps
bike innertube
long bar clamp
acetone (for clean up, it dissolves any uncured resin so you can clean it off of scissors or something)

I used two different sizes of pvc; a 1-1/2 inch ID tube for the top tube and down tube and a 1-1/4 inch tube for the seat tube. Cut the pvc tube to about 3 feet long. Now cut the tube down the middle(from end to end, a band saw works best because it has a thin blade) mark and end to ensure proper alignment when making a carbon fiber tube.

Cut the bike innertube to 4 feet making sure the valve is close to one end( about 8 inches from one end). Put contact cement on the inside of the tube on both ends and press them together when tacky, now tie a knot where the contact cement is. This creates a good seal for the tube when it is inflated.

DO A DRY RUN BY INFLATING THE INNERTUBE IN THE PVC PIPE WITHOUT ANY FABRIC

Wrap the innertube in two layers of peel ply. cut holes for valve.cut some fabric to make the tube (I went with 26 inches wide by however many layers you want in the tube) I used the light twill fabric on the top tube and down tube, about 5 layers on each( circumference of a circle is pi x diameter). For the seat tube I used a unidirectional fabric for the 2 inner layer and the twill for the outer(you may have to make a couple tubes because you need the inside diameter to be within the range of available seat tubes(25.2mm to 27.2mm, I took my seat tube to a local bike shop and they had one that fit nicely)  

Lay the carbon fabric on a surface (we have a disposable waxed paper covering on the tables) to wet it out. Make sure you wet it out thoroughly (the inflation process will squeeze some excess resin out). Then wrap the fabric around the inner tube. Make sure it is tight because you have to place it in the pvc tube and clamp it shut without the pvc pinching the fabric. Wrap another layer of peel ply on the outside of the wet fabric (so it wont stick to the pvc).

Make sure the innertube is inside the pipe, then place the end caps on the tube and clamp the tube together. Then tighten the pipe clamps spaced evenly along the pvc pipe. Inflate the innertube to about 30 psi. Much higher will pop the inner tube in my experience.

For the stays i wrapped the unidirectional fabric around a wooden dowel.first wet out the fabric and let it sit for about an hour(or until the resin is tacky) then wrap it around the dowel, this makes sure the fabric is tight and wont slip on itself, then I braided( with a braiding machine) around the dowel and fabric to compress it ( it makes a nice pattern). you can do this by hand( not braiding but compressing with a yarn)

for the metal tubes i first wrapped them in fiberglass fabric to prevent galvanic corrosion. I did some reading on this and found that everyone has a different opinion of how fast it occurs. to be safe I insulated the metal parts with fiberglass. make sure to remember the dropouts later). I put the tubes in a vacuum bag to ensure compression( you could do this with the electrical tape trick on some other bike instructions)
<p>i really wished you would have used the image side by side with instructions for easier understanding. you have obviously did not thing the readers were not there with you when you built this.</p>
<p>It's the way that the website is set up. When you write an instructable, you type out east section, then below that there is a place to add your photos or videos. When the website displays the instructable, it shows the photos for each step, then the instructions. Thats why sometimes you'll read an instructable and the author with say &quot;in the picture below&quot; when the pictures are actually displayed above.</p>
Hello! I was a student of Desing and Production of Composite Materials, but in Ukraine :) I have made a quite wide research, and of course i have read the articles you refer at first page. I am really interested in building a carbon frame, for fixed gear bike as well as you. Nice project! Especially I like the way you made tubes using innertube as a pressure bladder. The pressure you get was 30 psi, which is twice bigger comparably to vacuum method. Applying bigger pressure improves material quality. I think it is possible to reach 3 and more atm. pressure if using stiffer tubes and mount plugs tightly. Why didnt you make the rear stays the same way? Simply braiding them with yarn seems deficient. Instead of using wooden rods , luminiscent lamps may be used. They have cylindrical shape, and there are various sizes of them. After curing you can simply brake it and remove from inside the tube. I also dislike the tubes joints. Some builders wrap the joints with cloth and used a vacuum bag. Another way, which is my own idea, is to wrap joints with some tight elastic tape after laying wet carbon. The pressure will squeeze the epoxy out and impact fibers. A peel ply is required to soak the excess of epoxy. <br>I have some questions also:<br>- How much the frame weights?<br>- Did it crack?) If it did, where was the weakest place?<br>- What was the composite pattern, I mean how much layers were there and in what directions they were layed?
Hello! I was a student of Desing and Production of Composite Materials, but in Ukraine :) I have made a quite wide research, and of course i have read the articles you refer at first page. I am really interested in building a carbon frame, for fixed gear bike as well as you. Nice project! Especially I like the way you made tubes using innertube as a pressure bladder. The pressure you get was 30 psi, which is twice bigger comparably to vacuum method. Applying bigger pressure improves material quality. I think it is possible to reach 3 and more atm. pressure if using stiffer tubes and mount plugs tightly. Why didnt you make the rear stays the same way? Simply braiding them with yarn seems deficient. Instead of using wooden rods , luminiscent lamps may be used. They have cylindrical shape, and there are various sizes of them. After curing you can simply brake it and remove from inside the tube. I also dislike the tubes joints. Some builders wrap the joints with cloth and used a vacuum bag. Another way, which is my own idea, is to wrap joints with some tight elastic tape after laying wet carbon. The pressure will squeeze the epoxy out and impact fibers. A peel ply is required to soak the excess of epoxy. <br>I have some questions also:<br>- How much the frame weights?<br>- Did it crack?) If it did, where was the weakest place?<br>- What was the composite pattern, I mean how much layers were there and in what directions they were layed?
Aerospace companies use lightweight foam and then don't have to remove the tubes. Could using foam simplify the process at all?
It could in theory. I ran into two problems with this approach. The first being compaction of the layers of fabric. With my method i was able to compress the layers with 40 psi which makes a pretty good composite part. You could vacuum bag the fabric covered foam mandrel but you could get wrinkles. I also noticed the part could warp without a rigid mold to brace it in the vacuum bagging process.
Very Nice Prototype and also a Fellow Bama citizen too. I wonder what you are up to now, since it has been awhile since this project. are you finished with College and off in some Lab creating some other new and great stuff ? Thnxx for sharing you project with us, also it is awesome to see the good old American know-how applied to something simple like a bicycle but using high technology materials. Good Going ! +99
Thanks for the feedback! It is my last semester at Auburn which means I'm working on a senior design project. My team's project is to design a composite wheel to be used by the Formula SAE car team at Auburn. I will probably make a few Instructables out of the project so stay tuned!
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. <br>
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.
could you use small funnels?
Could this be used to make a hardtail frame?
The jig would look a lot different. Your downtube would need to be moved to accommodate the wheel traveling with the suspension.
Could you use a Carbon fiber kevlar blend?
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.
Oh and I also might add,<br><br>Installing the Drive arm on left side makes no difference in unthreading of the BB.<br><br>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)<br><br>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.<br><br><br>
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.
Hello Pankake.<br><br>I have really enjoyed reading your post!<br><br>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. <br><br>Hope this helps!
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.
velo-orange makes a threadless bottom bracket that would work too:<br>http://store.velo-orange.com/index.php/components/bottom-brackets/grand-cru-threadless-bottom-brackets.html<br>
hey have you ever thought of just using pre fabricated sheets? what are your thoughts on those?<br>
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.<br><br> Is this what you are talking about?
here is a link... couldnt you just wrap the sheets around a tube?
I don't see any link there. Could you try posting the link again?
So sorry bout that bro here you go http://www.carbonmods.co.uk/Departments/carbon-fiber-kits.aspx
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.
dude thanks so much your awesome.
I think this is the best enter instructable in the bike constest so far!
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.<br>&gt;G
The frame stiffness is great. I can feel the road but it isn't jarring. <br>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.
This instructable has definitely placed building a carbon fiber bike back on my to-do list! Thanks!<br>What do you think the total cost for parts was?
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.<br><br>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?<br><br>I didn't get cheap parts stuff because I plan to use most of it for a long time<br>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.
exelent frame, i like it. And the left side chain is a good detail.
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. <br>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!
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.?
Yes, that is why I made a fixed gear for my first attempt.

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