This is my second broken carbon bike I turned into a Bamboo and Hemp bike. This bike looks amazing in person, and rides really well too. The stiffness of this bike is unbelievable. I highly recommend making one. You can view the entire process, plus the build of another bamboo bike at the AdventureSeed Blog.
If you want the reasons I made some of these decisions, read the build for Bamboo Bike number 1. It explains a lot about why some decisions were made and gives more details on the jig
I have only a few tools available to me, so I hope this is useful to the rest of you garage builders who don't have extensive shops.
This is bamboo bike version two. It was built in a weekend. It is meant to correct the problems of version 1- cracking tubes and poor ride quality. The seat mast idea on version 1 was inspired by the LOOK 595 we demoed, but the bamboo didn't work well because of the length of the mast and bamboo's tendency to split if you put anything inside of it.
Materials changed, as we decided to go cheaper and more accessible on this one. Also, we went to Jungle Supply for the bamboo, and the selection was bigger.
If you do like this instructable, check out the blog at AdventureSeed.com for similar DIY projects and awesome stuff.
Step 1: Assemble Materials
Epoxy - Tap Plastics - $40/qt, but don't buy this. Any low VOC (less toxic) laminating epoxy will work. I recommend System Three, West Marine MAS Epoxy or Resin Research Get a quart
Hemp - Craft store - $10 A full large roll of hemp was used.
Tools - Dremel diamond cutting bit - $15, wood cutting bit $15. Available at Home Depot too
Gorilla Glue - Home Depot - $10
Frame Jig - Ours is build from Aluminum Extrusions. Plywood or MDF can work if you have the capacity to make it. I don't have enough tools for that.
Step 2: The Jig
The same picture frame jig from bike 1 was used. Picture frame style made of 8020 ebay garage sale aluminum extrusions, with various bits and pieces, and centering cones from ebay
We agreed that the Specialized S-Works Tarmac was an excellent frame, so we put one in the jig and got everything tight. Having a bike to use as a template helps a lot in our setup, because there is slop in a lot of the screws, plates, and moving pieces. If I were to build another jig, it would be with Misumi Extrusions. They are cheaper, all metric (standard caused problems), and have an enormous selection. They also have no minimum order. Their catalog is a garage engineer's dream.
Step 3: Cutting Out Old Carbon
With this in mind, we took out the tubes to be replaced by bamboo. Again, we didn't have the technical resources up the rear dropouts well, (if we'd used Misumi Extrusions we would) so we spared the rear triangle. We also spared the seat tube clamp area, so the seat tube would have a nice interface.
The dremel diamond wheel cuts carbon like butter. The other bits won't, so this piece is necessary if you want to do this without a headache. Get goggles and a mask. Cutting is dusty and particulate carbon causes a whole pile of health problems later in your life.
Step 4: Miter the Bamboo
Choose sections of bamboo with NO cracks. Even hairline cracks. Cracks will grow and never go away. Cracked bamboo is worthless, so make sure you have enough without the cracked sections.
Using the vice, dremel wood cutting tool, and sanding bit was a nice combination. Compared to a file, this is light speed construction. Don't push too hard on the bamboo ends, as you don't want to crack the bamboo. This is more likely with a file and saw than a dremel. Our miters were pretty sloppy and it ended up ok. Less sloppy is better, but don't ruin your day over it. It just has to fit nicely.
Step 5: Glue It Together
The last bike convinced me that the hemp lugs are the most structural element in bike, and the joints matter much less. Instead of ordering another tube of T-88 structural epoxy (awesome shear strength) we just used Gorilla Glue. Once the miters were right, the bamboo was glued to the old carbon and metal bits (still in the jig) and left overnight with a little tape to hold it in place.
My suspicions were confirmed, by the way. The finished bike has no problems structurally, and is very stiff
Step 6: Prepare for Lug Layup
The shiny, outer layer of bamboo doesn't stick to epoxy well. Use this to your advantage. Remove the outer layer with something abrasive and expose the woody under layer wherever you're going to build the lug. We planned for about 4 inches of lug on each tube. This is more than version 1, but we're not trying to win a weight contest.
Step 7: Layup the Lugs
Many brands brag about their layup schedule- the direction the carbon fibers are laid down. We just try to wrap the hemp from tube to tube, as that looks the most structurally sound.
We found mixing small amounts of epoxy, soaking a hemp string with it, and wrapping the joints one by one was the best technique. Using the hemp string instead of the raw fibers made the structure much heavier, and used a lot more epoxy,
but was so much easier that the raw fibers aren't worth the trouble. Then we wrap the joints with electrical tape sticky side up to squeeze out the extra epoxy from the layup
There is a tricky part to this, and that is figuring out the best time to pull the tape off. Wait too long and the epoxy will attach the tape to the bike. Try too soon and the expoxy will be too wet and sticky to get the tape off. There is no magic formula, you just have to figure this part out.
Step 8: Add Components!
Bike number 1 was noodley, no doubt. It was the flexiest bike ever made. This one is stiff as hell. It rides amazing as well. The larger diameter bamboo, hemp rope lugs, and now that the bike is finished, I must say that this is worth the weight. The quality and look are both amazing.
Now just add some sweet components that are worthy of your amazing new frame. I personally love singlespeeds for zooming between bars, but the options are infinite, and up to you.
Again, I didn't document very well WHY i made the decisions I did in this instructable. Refer to the bamboo bike number 1 if you want to understand better why the decisions were made the way they were. There are more details about the jig at that page too.