I saw a picture of a bamboo bike and decided I had to have one. I found out that professionally built bamboo frames cost a few thousand dollars so I decided to build one myself.
I had a lot of fun and I hope that you can make one too by following these instructions.
The bike I made is a track bike for commuting to work. The bicycle was inspired by Craig Calfee who makes much nicer bamboo bikes. I really wanted something with a minimum of fancy technology and carbon fiber (although I sprang for the carbon fork). I used epoxy and hemp fibers on all the joints (no pun intended). The track bike also makes it easy in that it is a very simple bike - no gears, cable routings, rear brake or derailers.
Disclaimer: Death or serious injury can result from a bicycle frame failure. Using new and untested techniques is risky. Be smart.
Some links to check out before you get started:
Brano's instructable on carbon and bamboo bike building
Craig Calfee's bamboo bike project
Calfee bamboo bikes
Bike Forest BikeCAD
The forum for info on bamboo and heat treating it
The basic steps:
1. Figure out what type of bicycle you want
2. Get all of the parts and bamboo
3. Heat treat the bamboo
4. Tack it all together
6. Epoxy it all together
7. Build up bike
8. Ride off into sunset
Step 1: Pick the Bicycle Frame You Want to Build
If you are a real bike nerd you will love this step. You are now a frame designer and get to think about things like bottom bracket drop, chain stay length and head tube angle.
I suggest using an existing frame as a template (if you have one you really like).
If you feel ready to test your skills of an artist go to www.bikeforest.com and use the BIKECAD program. It is a free, online frame designing program.
Another good source of information is the Paterek Manual, which is actually for steel frames. Paterek goes into detail on how to size a frame based on body measurements and what each change in geometry means as far as road handling goes.
Once you have your geometry picked out draw your frame on a large piece of paper.
Step 2: Get Your Parts and Bamboo
There are some parts that you simply can not use bamboo for (maybe you can, but I didn't)
2. Bottom bracket shell
3. Head tube (I tried bamboo and it did not work - too wobbly)
I chopped the dropouts off an kids bmx which are very similar to track dropouts. The bottom bracket shell was cut out of a wrecked road bike frame. The fork I ended up getting was a carbon road fork from Nashbar. The pink one was just for sizing purposes.
I had no idea what to get so I went to my local bamboo nursery and bought some hefty green pieces of bamboo. The size I chose was about the same diameter on say an aluminum bike.
Step 3: Heat Treat Bamboo
Sometimes being impatient pays off!
The bamboo I bought was green and freshly cut. I realized that it would have to be dry before I could use it but I wanted to use it right now! A brief interweb search tought me that bamboo can be heat treated. So I busted out the trusty old blowtorch and got to work on some test pieces.
Holy cow, heat treating bamboo is amazing. Steam and water literally spews out the ends. Sorry I don't have a picture of this (I was using both hands and recently broke up with my girlfriend so nobody was there to take pictures).
Practice on a few pieces first. The trick is to heat the bamboo evenly and slowly. The two step process worked best for me. The first step is to turn the green sections to a light brown. The second step is turn the light brown sections to a dark brown.
I also had a few dry pieces (already light brown) and only treated them once to get them to a dark brown color.
Another thing, I only did one section at a time (from one node to the next).
Heat treating turns relatively soft bamboo into a super hard material. It is incredible. My wood saw had no trouble cutting the green bamboo but I had to use a hacksaw to cut the treated bamboo.
Step 4: Tack Frame Togther
Now that you have heat treated the bamboo you need, cut, miter and tack the frame together.
You may choose to use a jig to hold everything in place. I did not use a jig so I am not going to go into that here. I don't know much about jigs so don't even ask.
I used the full size drawing and built directly off of that using spacers and standoffs to get everything in the right position.
Use a good half-round wood rasp to miter the joints.
Make sure that you use trigonometry to figure out the length of the chain stays and seat stays. What is drawn on the paper is a projected view.
Rough up the bamboo where the epoxy will go.
Rough up the metal too and stick it all together using 5 minute epoxy or your favorite glue.
Once it is all stuck together very gently put the wheels and fork in place and check alignment. If it looks good you are ready to move to move to the next step. If not
Note: The bamboo headset shown was not a good idea. I had to ream it out and insert a steel head tube because the headset cups did not seat properly in the bamboo and gave a scary wobble when turning corners! Start with a metal head tube and save yourself the hassle. The picture does show how rough your bamboo joint areas should be.
Step 5: Epoxy It All Together
Time to get dirty!
I used epoxy from fiberglass Hawaii called Aluzine (it is a 2 to 1 epoxy specially formulated for surfboards and has some UV inhibitors in it). Why? Because I had a lot of it left over from a repair to my windsurfer.
I used two different kinds of hemp fibers. I used raw hemp fibers (or semi-processed) and hemp twine (drawn out - semi-twisted, comes on a spool). The raw hemp seems much stronger so I used that as the bulk of the joint and then used the twine to tighten up the lashings.
Mask the frame off carefully. Prepare all the joint areas (clean and dirt free, heavily sanded or rasped for an extra-rough surface).
The process is pretty messy and requires a lot of patience and finesse. Wear gloves and start small - small batches of epoxy and small amounts of lashing. I mixed up a small pot of epoxy and then dipped my fibers in it. I then wrapped it on the joint and followed that with a dry piece of twine. There was enough epoxy on the raw fibers to completely wet out the twine. Practice and you will get it.
I got my hemp from www.downbound.com
Of course you can use kevlar, carbon fiber or fiberglass.
Step 6: Build Up Bike
Now you get to put in a bottom bracket and a head set. Stick on the cranks and chain, add the wheels and bar and the seat post.
Oh yeah, the seat post...
I thought my idea of having the seat post made out of bamboo was really cool. I spoke to my local bike guru who explained that the seat post is integral to the strength of the frame and advised that I insert a steel seat post into the bamboo tube. Luckily seat posts come in a wide range of widths. I folded a small piece of sandpaper in half (rough surfaces out) and wrapped that around the seat post to allow the bamboo to grip it. I then cut two slots in the bamboo to allow the seat binder to clamp the bamboo down on the seat post.
It all worked but then, crack! I guess the sandpaper was too much for the diameter of the bamboo and caused a small crack down the length of the seat post, almost all the way to the binding. I drilled a small hole to stop the crack spreading and now I will have to wrap the post in some hemp and epoxy.
I still rode it like this and it seemed ok but I am in the process of fixing it right now.
I also had to file down one of my joints at the dropouts to allow some clearance for the chain.
Step 7: Ride Off Into the Sunset
So how does it ride? Like a stealth bomber! The ride is smooth and silky and very quiet. I never realized how much noise a steel bike makes as you go over bumps and potholes. The bamboo bike is quiet.
Riding around on a bike you built yourself is thrilling.
I am still a little nervous about it breaking but every week I am getting less freaked out about riding it. I think the bike needs a name so if you have any suggestions...
The bike is actually not that light. It weighs about what my steel fixie weighed when built up - around 18 or 19 lbs. I will weigh it again and let you know.
Step 8: Sweet Pictures to Further Inspire You...
I took these of a Calfee bike parked outside the library - so awesome!
CobyUnger made it!