http://www.bikeforums.net/attachment...7&d=1268075349

That deserves to be seen full size.
Old Goat, that is a beauty.

That turned out really nice.
A tip that I should have mentioned is that you can dry wrap the carbon and make it quite a bit more manageable. Mix your epoxy and paint a layer over the lug area then wrap the dry carbon over the epoxy. It will wet itself by the epoxy squeezing up through it. Then when you've completed the wrap you can paint another layer of epoxy and then wrap it with the tubing strips.
I only went through 3 pairs of gloves so it is quite a bit neater.
Enjoy your ride.
I'll be posting my latest one soon.

Here are some pictures that I took during the build of my first bamboo frame.I learned alot from this project so the next one will be easier.

Here's my latest. Set up fixed but convertible to geared with addition of cable stops etc.
http://i399.photobucket.com/albums/p...h_CIMG5917.jpg
http://i399.photobucket.com/albums/p...h_CIMG5919.jpg
http://i399.photobucket.com/albums/p...h_CIMG5920.jpg
http://i399.photobucket.com/albums/p...h_CIMG5921.jpg
http://i399.photobucket.com/albums/p...h_CIMG5923.jpg
http://i399.photobucket.com/albums/p...h_CIMG5924.jpg
http://i399.photobucket.com/albums/p...h_CIMG5925.jpg
http://i399.photobucket.com/albums/p...h_CIMG5928.jpg
http://i399.photobucket.com/albums/p...CIMG5929-1.jpg
http://i399.photobucket.com/albums/p...h_CIMG5930.jpg

<p>Problem #1. Hi modulus (stiff) lugs or wraps of carbon, steel, or whatever joining low modulus (flexible) materials like bamboo or wood are a prescription for failure. The flexible material bends against the unyielding material of the connector and will ultimately fail at that intersection. Don't have to take my word, Calfee abandoned carbon wraps for that reason. They changed to hemp for a lower modulus connector, but the result of low stiffness materials throughout results in a flexible frame, duh. In any event, I doubt the hemp solved it, because the modulus of epoxy can't get down to bamboo.</p>
Problem #2. Bamboo or wood absorbs moisture naturally and that cannot be stopped by paint or oil finishes. The force of expansion due to moisture against an unyielding lug exceeds the proportional limit of the expanding material, causing the cells to collapse at the perimeter. When the moisture content decreases, as it does seasonally, the bamboo shrinks in the connector, loosening the joint. Eventually the joint will fail, not too eventually at that. Yeah, yeah, I know some Princeton engineer is doing this, he must have slept through the materials science classes, it's just elementary stuff.

Theory and science versus practical application. Know your materials and balance their strengths and weaknesses.
I can see how a totally unyielding Carbon/Epoxy wrap and poorly acclimated bamboo could cause these problems but the key is to get your bamboo down to maximum shrinkage and use an Epoxy and Carbon with a modulus that matches the Bamboo more closely.
The trend did seem to be towards "Aerospace quality high modulus carbon" and the absolute best Epoxy there was. Then I can see the disparity causing problems.
But in practice Epoxy/Carbon is nowhere near as unyielding as you seem to think. Particularly when the joint feathers into the bamboo and distributes those stresses over a larger area.
Many things are made from natural materials that undergo moisture and temperature cycling with a bit of care. Wooden Kayaks and Airplanes, Bamboo fly rods that are 100 years old and still going strong.
It takes very little extra effort to not leave your bamboo bike lying around in a damp environment or baking in a sweltering area.
There is also Epoxy designed for materials with different thermal coefficients.

I have just begun building a bamboo bike, and have already treated the bamboo. I have been looking at carbon fiber tow, and was wondering if this one would work:

http://cgi.ebay.com/ws/eBayISAPI.dll...#ht_1469wt_283

It lists the resin it uses, but I do not know if that affects the ability to use it with other epoxies. Also it is 12k, but I don't know if that will make much of a difference. Does anyone have any opinions on this tow? It much cheaper per yard than anything else I have found.

You don't need 5,000 meters of carbon tow....unless you plan on building like 5 bikes. I don't know about 12k tow, I've only used 3k. It might be a little bit harder to work with because it is larger.

Oh, I know I don't need nearly that much. It is just that the item above is by far the best deal on carbon tow I have found yet.

Just wanted to say that bike is freaking amazing.

I just built an accessory for the frame I will be building:

http://img404.imageshack.us/img404/1634/p5200098.jpg
http://img517.imageshack.us/img517/5245/p5200097.jpg

It is not quite finished yet, as I have not finished the bamboo, but I am really pleased with the way it turned out. At first I was worried about strength, but this bamboo easily supports much more than my weight. Clamping it to the stem has not been an issue either.

I did the same thing for my bike. Did you heat treat that bamboo? It seems to be less prone to cracking if you do, but it would also make it darker.

Yes, I heat treated it and then sanded it a TON. I am still a little worried about it cracking where it is clamped, so I might wrap around that area with carbon and epoxy once I get the materials, to give it strength in that direction as well.

You should soak the inside of the bamboo tube in Epoxy and put a piece of dowel inside the portion where the clamp goes. That will help support it there.
If the piece of bamboo is perfectly round it can withstand very high crushing forces if they are distributed evenly from all sides. It's a bit like crushing an egg by forcing in from either end.

Have you done that before? I wanted to try it, but couldn't figure out a good way to do it.

Yes I have. Plug one end and pour Epoxy into the hollow. Let it sit and soak in for about ten minutes or so (depending on pot life of your Epoxy). Pour out the excess. Soak a pre-fitted piece of dowel and then slide it into the bamboo tube so that it ends up centered. Allow the Epoxy to cure. It is a good idea to cure the tube lying flat and roll it periodically as the Epoxy sets up so that it doesn't pool on one side of the tube. You can also cap the ends of the tube. You may just be able to fit some wooden nail or screw plugs which you can buy pre-made from any Home Depot etc.
That will give it a finished look to match the general natural look.
eta: Here's what i mean by screw plugs or "buttons": http://www.widgetco.com/wood-buttons

Haha, that's awesome. I'll see if I can find those.

Some great looking bikes in here. I'm planning a build right now. In fact I harvested some bamboo locally today.

I am also doing a preparation step that I haven't seen employed yet. I put the cut whole bamboo plants into water. This way they will continue photosynthesizing until all of their carbohydrates are used up. This is done in hopes to reduce chances of any type of microorganism thriving on my frame material.

Now I need a donor frame!

I've been working on mine for the last week, and now the frame is completely tacked and ready to be wrapped. The BB shell, dropouts, and head tube were all taken from an old steel Astrale frame. More pics to come soon!

http://img819.imageshack.us/img819/1272/p6090245.jpg


You can see the bobbin of CF in back to the right. It is freaking massive- I decided to go with the 5000 Meter roll of 12K Tow.

Make sure you work some glass into the BB and Head tube to prevent corrosion. Not sure it's as bad with Steel/carbon but it won't hurt. Looks like you may have been able to get a bit more insertion into the chainstays with your dropouts.
You can always build up an epoxy fillet with some fairing compound and blend that juncture before you wrap it. You can usually buy wood flour, chopped or milled glass, cotton fibers etc to make a thickened mixture to fill in areas and blend curves.

How close to the bottom bracket shell do you guys cut the chainstays off?

I gave it about an inch on the chainstays, including the lug. If I had done any more than that I would have had to cut slightly wider diameter bamboo, which would have cut down on wheel clearance.

I just recently built a bamboo frame. It turned out decent for my first one, only there is a little flex on the top tube and down tube so I think I need to use a larger diameter bamboo. Anyone know the best way to take off the existing fiberglass and epoxy/resin so that I can reuse the existing steel parts? Thanks in advacne

^^^
A drimmel.

I'm getting really close to finishing my frame. All that is left is sinking a shim for the seatpost and finishing the bamboo. What do you guys recommend to get a semi-gloss or satin coat? I'm afraid something traditional like polyurethane would be too brittle and crack.

http://img809.imageshack.us/img809/4596/p7050335.jpg