The Final Frame

Bamboo Bike Final Documentation

1.

For my semester long fabrication project I decided to build a bamboo bicycle frame. I started out by doing a lot of research on bamboo and its strength properties to see if bamboo bicycles were as reliable as people claimed them to be. I found out that bamboo have similar strength properties to aluminum, so I concluded using bamboo as tubing for a bike frame is perfectly reasonable.

Going into the fame design process I initially designed a mountain bike frame using Bike CAD Pro, but then because of availability of bamboo I had to change my frame design to a road frame.

The next problem I faced was figuring out how to join the bamboo tubes. Commercial bamboo bike frame builders use either internal or external carbon fiber or sometimes even metal lugs to hold the tubes together but I wanted to experiment with natural fibers, so I chose to use hemp. I ordered several hemp fabrics samples and did tests on which were strongest and which adhered best to the bamboo using epoxy, which was my adhesive of choice for this project. I chose to go with hemp canvass because it was more durable and because it was thicker soaked up the epoxy and held the tubes together the best.

I machined my own head tube and bottom bracket out of steel for my bamboo frame and purchased dropouts, which I had to modify slightly to work with my frame.

Before starting building the frame I had to first heat-treat all of my bamboo. To do this I first got most of the moisture out using a propane torch, then I bakes the tubes for an hour at 350ºF.

When building the frame I decided to use foam lugs to hold the tubes together while I raped them in epoxy impregnated hemp canvas. I was fortunate, the epoxy resin I used did not react chemically with the foam and eat away at it, it actually absorbed some of the epoxy providing a stronger bond.

2.

Testing will be done this summer when I return to California where I have the parts to finish building up the bike.

3.

The final status of the project as of now is a completed bamboo frame. As I said above I will test out the frame this summer back in California.

4.

If the frame does fail during testing I will have to figure out a better way to hold the tubes together. I imagine if the frame is going to break it will be at one of the tube junctures.

5.

N/A

6.

I did all the fabrication and documentation of the project.

7.

I originally was going to bet bamboo from a bamboo bike manufacturer in New York who grow and heat treat bamboo specifically to make bikes out of however that fell though so I had to order the largest diameter bamboo I could from a fencing company in New Jersey. I go the bamboo for my chain and seat stays from Triple Brooke Farms in Massachusetts.

Another problem I encountered was precision in frame alignment. There is no good way to align a bamboo frame.

Build Update

I've cut the tubes to length and have rough cut the foam lugs to hold them together. Next step is shaving down the foam to look sleeker and then start wrapping the tubes.

Bamboo Bike Update

Ok so things have been going slower than I had hoped mostly due to my involvement in a play on campus and my bamboo contact falling through but there is still plenty of time.

On April 10th I went to Triple Brooke Farms to cut down my own bamboo to use for the chain and seat stays. There I met with the owner Steve who walked me around the farm and told me about the different species of bamboo he has.

As for the bamboo for my main frame I've had to order out of state for it because finding large diameter bamboo in Massachusetts is hard this year due to the awful winter we had. That being said I've also had to change the design for my frame to use smaller diameter tubes, so my design has gone from being a mountain bike to a road bike because I'm concerned about the smaller diameter tubes handling the stress of mountain biking. Also to increase rigidity I'm going to use high density insulating foam to lug the tubes together before wrapping them.



Last week I heat treated my chain and seat stay tubes. To prep the tubes for heat treating I first rough cut them down to size and then drilled a very small hole in each clum to allow steam to escape. I used a propane torch to get the majority of the water out of the tubes, which turned them from their natural green to a really pretty golden marshmallow color, then I baked them at 350ºF for an hour to get the last bits of water out.



One question that I am still left with is how am I going to attach my dropouts to my seat and chain stays. Right now I think I'm going to weld tubing onto them to act as lugs and then wrap around the bamboo and steel lugs.

Hemp!

Today in class I ordered the hemp fabric I'm going to use for lugging the tubes together. I decided to go with hemp canvass because it is more durable. I also ordered a sample of 70% Bamboo 30% hemp fabric, just to check it out cause it sounds cool.

Metal Parts

I machined my own 68mm BB and cut from some stock tube a head tube for my frame. I'm a little displeased with the threads of my BB but they should work fine. The dropouts I purchased from Salsa came in and I even got a headbadge for the frame.

Plans for the rest of the semester

3/28: order supplies and finalize bicycle designs
4/4: Start mitering tubes this week and hopefully finish
4/11: Start wrapping tubes

*The week of the 4th is tech week for a play I'm involved with so I may not get as far as I hope to that week