Build a Bamboo Bicycle (And Light It Up!)

If you have ever wanted to build your own bicycle frame, but can't afford a framebuilding class or the materials to braze a frame, building one out of bamboo and carbon fiber is a great and relatively inexpensive way to get started.  In this Instructable, I will explain in detail how to build a great looking bamboo frame.  After that, you will learn how to make some LED spoke lights to go along with your DIY bike, or any other bike you want to put them on.

WARNING:  If you are not comfortable with being stopped by strangers and answering their questions about your bicycle, this is not the project for you.  And DEFINITELY do not build the spoke lights.

For the bicycle frame:

• Bamboo:  I used 1 7/8" diameter for the down tube, 1 3/8" for the top and seat tubes, 15/16" for the seat stays, and 1 1/16 for the chain stays.  All values are approximate, and anything close to those should work.
• Carbon Fiber Tow:  I got 5000 meters of it off ebay for 50$.  I have enough left over to build at least 4 more bikes.
• Epoxy:  I used West Systems 105 resin and 205 Hardener.
• Old Bicycle Frame:  I chose to cut apart an old frame for the lugs, rather than buy new ones.  Using an old frame also lets you get away with not building a proper jig.
• Propane Torch:  For heat-treating the bamboo.
• Basic hand tools:  Saws, a decent knife, a drill, a rotary tool.
• Electrical Tape:  For compressing the carbon fiber while the resin hardens.
• Aluminum angle bar:  For making a simple stand to hold the frame in place.
• Threaded rod and nuts:  For holding the dropouts in place in the stand.
• Spar Varnish:  For finishing the bamboo.
• Paint remover:  For stripping the old frame.
• Sand Paper:  For sanding, of course!
• Rubber Gloves:  For working with epoxy.  Apparently, you can develop a nasty allergy from too much skin exposure to the hardener.  You will need at least 50 pairs of these.

For the lights:

• 4 square wooden dowels
• Drill and 1/16 drill bit
• 80 LED's:  I used 3mm orange ones
• 2x 9V battery clips
• Resistors:  To run the orange LED's off 9V, I needed 20x 30 Ohm resistors
• Electrical tape
• Soldering Iron

I cut down my bamboo green, so I heat treated it with a propane torch to remove some of the water and harden the bamboo.  Heat treating also gives the bamboo a nice golden color.  

To start, use a long metal pole such as a gardening stake to punch out all the nodes.  If you do not, the heat can cause the nodes to explode.  Light your torch, and begin heating the bamboo, node at a time.  You will know when you have heated it enough, because the green will suddenly  turn tan or brown.  Obviously, try not to actually burn the bamboo, or you will weaken it.

After you have torched the bamboo, it is probably best to let the poles sit for a month or so to let the rest of the water escape.  Once my bamboo was dry, I sanded it down past the outer skin.  In my opinion, the bamboo looks much better this way, as it has a beautiful gold color under the skin.  I sanded down the nodes even with the rest of the bamboo as well.

I did not want to build a full jig, but I still built a stand for the frame.  This helped enormously with wrapping the carbon fiber and aligning the dropouts.  

I screwed two pieces of aluminum angle into a 6" wide plywood board to hold the bottom bracket shell in place.  To hold the rear dropouts, I used a threaded rod bolted to the wooden base.  

Having a donor frame to cut apart makes it possible to build the frame without building or buying a jig.  If you can find one for free or at a garage sale, it also cuts down on costs, because you do not have to purchase a head tube, bottom bracket shell, or dropouts.

To get the frame ready, strip the powder coat off the head tube, BB shell, and dropouts using paint stripper.  Beware, this is pretty nasty stuff.  Use it outside, and try to keep if off you.  

To avoid using a jig, the order in which you remove the bike's tubes is very important.  You have to be able to retain the bike's geometry for everything to align and for the bike to track straight.  I started out by removing the chain stays.  By removing them first, the dropouts are still held in place by the seat stays, and no other part of the frame is affected.

The first tubes I replaced were the chain stays.  I used quite wide diameter bamboo to avoid flex in the BB area.  Before replacing the tubes, I built up the dropouts with carbon fiber so that they fit snugly inside the bamboo tubes.  I then sanded the metal to help the epoxy grip, and fit the bamboo in place, tacking it in place with epoxy.  As you can see, the bamboo is heavily sanded on the outside.

After the chain stays, I added the bamboo top tube, seat tube, and seat stays all at once.  I started out by mitering the top tube on the head tube side.  I then cut the original top tube off, to figure out the correct length of the new bamboo one.  Once the top tube was cut to the appropriate length, I removed the seat tube and chain stays.  The bamboo seat tube was mitered to fit around the BB shell, the top tube was mitered to to fit the seat tube, and the seat stays were mitered to fit the seat tube.  If you have them, you can use a hole saw and a drill press to do the mitering.  I do not, so I used a Flexcut woodworking knife.  Once all the tubes were cut and mitered, I tacked them in place with epoxy.  Alignment was done by eye: I used the down tube as a reference.  A easy way to hold everything in place while the epoxy is drying is to wrap it in electrical tape.  It may not be the most elegant approach, but I found it works quite well.

Before replacing the down tube with bamboo, I had to strengthen the seat cluster with some carbon fiber.  If I had not, the joint may well have cracked apart when I inserted the down tube, because I had to bend the frame slightly to fit it in.  I will go into more detail about wrapping the carbon fiber in a later step.  

I chose to used really wide diameter bamboo for the down tube.  I really like how it looks, and it adds a lot of stiffness to the frame.  The down tube was mitered and tacked into the frame just as the other tubes were.

Now that your frame is tacked together, you need to strengthen the joints with carbon fiber.  This is easily the most time consuming part of the frame building process, at least if you choose to use carbon fiber tow rather than cloth.  

To start out, mask of your frame.  This makes cleaning up the tubes much easier, but be sure not to wrap over the tape at all, or it will be impossible to remove.  

Wrapping the carbon fiber is best done a little bit at a time.  I found that the easiest way to wrap was to paint some epoxy on the joint, wrap one or two layers of carbon around the joint, and then paint more epoxy on top of the carbon.  Repeat these steps until the joint is too soft to wrap much more.  When you have finished with the carbon fiber, wrap the entire joint in electrical tape, sticky side up, to compress the joint as it dries.  Once the epoxy is dry, remove the tape, sand the surface of the joint lightly, and add another layer of carbon.  Continue this process until the joint looks sturdy.  When you are wrapping, be sure that you have fibers in all directions.  If you just wrap circularly, the joints will only be strong in one direction.  This can lead to cracks or even joint failures later on.  To fix this, I cut lots of short strips of tow and laid them lengthwise on the joints, before wrapping circularly around them.  I alternated one lengthwise layer and then one layer around.  I have no idea how much carbon fiber is necessary, but it is better to have really thick joints than too thin joints.

Once the joints are strong enough, sand them down to a smooth surface.  This step is not necessary, but it makes the joints look infinitely better.  

Warning:  Epoxy dust and carbon fiber dust are not good for you!  The carbon fiber will irritate your skin and eyes (and probably your lungs), and epoxy is just not nice stuff, so be sure to do all your sanding outside, preferably with long sleeves and a breathing filter.

Depending on your frame's geometry, you may want to add a chain stay bridge to stiffen the frame.  Also add a brake bridge, and cable stops, if you need them.  For both these parts, I cut the tubes out of thin bamboo, and wrapped them heavily with carbon fiber.

While you are wrapping, occasionally check to make sure you have clearance for your back wheel's cassette.  I found that I had to remove a significant amount of bamboo and carbon to get them to fit.

If you are going to have a derailleur or rear brake on your bike, you can attach cable stops with carbon fiber as well.  To make the cable stops, I cut short segments of very thin bamboo, and glued  a metal cable cable cap into the bamboo.  I then glued the assemblies to the bamboo frame on the down tube, and wrapped around them them in carbon fiber.  For the brakes, I decided to run housing all the way along the frame, so I did not use cable caps.  I just cut short segments of bamboo to guide the brake cable and glued them along the top tube.

There are almost certainly going to be some pits or ridges in your joints that would be too difficult to sand out.  To fill these imperfections, I made my own epoxy filler out of carbon dust.  When mixed in with epoxy, this forms a black, tar-like glue that can be used like putty to fill in the gaps.  I made the carbon dust by filing down a piece of a burned wood.  I then used a super fine strainer to filter out all but the very smallest particles.  Once you have made the thickened epoxy, spread it generously on any imperfections in the surface.  Once it has dried, sand it down to the level of the carbon fiber.

Once your joints have been sanded down, you can simply paint a thin layer of epoxy over them to make them shiny and beautiful.  The bamboo, however, requires more careful treatment.  

First of all, sand down the bamboo, and remove any epoxy that might have gotten on the tubes.  To finish the bamboo, I chose to use some spar varnish left over from my boat.  Since this stuff it durable and flexible enough to be used on masts and spars, it should work quite well on a bicycle.  I thinned the varnish with mineral spirits, and applied about 10 thin layers of it.  Other people have used tung oil to finish bamboo instead.  I have only used it on wood, but, while it looks very good, it does not provide a hard coating like varnish does.  

This step is far from necessary, but making a nice head badge is a great way to separate your bamboo bike from all the others.  I made mine out of a segment of steel tubing cut from the donor bike.  Once I came up with a design (an Instructables Robot-esque one), I drilled the rough shape out of the steel using a fine drill bit.  Then I fixed the edges with a reinforced Dremel cutting disk.  I cut the lines into the badge with the cutting disk as well.  To get the lines to pop out, I colored over the entire badge with a sharpie marker, and then wiped it off with a rag.  The ink stayed in the crevices, giving the design some clarity.  I then put a clear coat of polyurethane over it, and epoxied it to the head tube.

If you have managed to build yourself a bamboo bicycle frame, you should be able to do this yourself, and I won't go into too much detail about how it is done.  If you need help, you can learn how without leaving Instructables:

https://www.instructables.com/id/How-to-Build-Up-a-Bike/

I built mine up with a mixture of new and vintage parts.  I bought a new carbon fiber for from Nashbar on sale for 52 dollars.  I highly recommend you get a carbon fork, simply because they perfectly match the carbon on the frame.  I got my brakes on ebay for 24 for the pair, I already had the wheelset, bars, shifters, derailleur, and cranks I used, and I got cables and housing from my local bike store.

Because simply having a bamboo bicycle is not unusual enough, you may want to add some lights to it to garner even more attention.  I built these simple wheel lights for the Halloween Critical Mass ride in Atlanta.  

The spoke lights are based off a very simple circuit.  Each one is composed of ten sets of four LED's and a resistor in a series, in parallel.  I chose to use 3mm orange LED's because they were for Halloween.

I used 4 thin square dowels to make the frame of the lights.  Drill 40 1/16" holes close together along the length of each dowel.  They must be spaced so that an LED's leads can fit into every pair of holes.  To space the LED's evenly, drill the holes in sets of four- one LED on each side of the dowel per set.  Then fit the LED's through the holes, alternating sides.  Make sure that the LED's are oriented positive to negative between each one.  Solder each pair of LED's together positive to negative.  Also join every two pairs of LED's the same way.  For every 4 LED's solder a resistor to the positive lead of the first resistor in the chain.  4 LED's and on resistor in a series make one node of the lights.  Each dowel has 5 nodes in parallel, and each set of lights has two rods in parallel.

Next, you need to wire each LED node together in parallel.  When doing this, try to keep the wire as close as possible to the dowel, so it does not get in the way.  Once you have wired together each dowel, connect each one to the 9V battery leads, with a slide switch to shut off the circuit.  Then wrap each rod in electrical tape to insulate the circuits.  To attach the lights to the circuit, first fix the 9V battery to your wheel's hub, using electrical/duct tape.  Then fix the rods to the spokes using zip ties or more tape.

Now, flip the switch and go on a bike ride!  Large ride like Critical Mass are great for demonstrating your bamboo bike with hypnotically glowing wheels.

This project was a great learning experience.  Although I think it turned out quite well, there are a number of things I would do differently again if I were to build another bamboo frame (which I may do, if I can justify having a 3rd bicycle).  First of all, I would coat the insides of all the tubes with a thin coat of epoxy, for protection.  Also, I would try starting without an old frame, so that I can tailor the fit to my body, rather than going with what I had.  I would also like to experiment with tube shape, i.e. building a TT type frame, with bladed tubes and a rear wheel cutout.

Please note that this Instructables is entered in the bike contest, and the MakerBot contest so please vote for me when the time comes!  500$ to REI could fund the components for building an even cooler bamboo bicycle, and with a 3D printer, I could print headbadges, so I don't have to arduously grind them out of steel.