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Carbon Fiber Bike

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Step 3: Making the Tubes

Picture of Making the Tubes
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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)
 
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