Bamboo MTB Frame (June 2004)

This is my second home-made frame. This time I used bamboo rods connected with carbon composite joints.

I have seen many amazing constructions made of bamboo and I always wondered, why such light, strong, stiff and elastic material is not widespread used for building of bicycle frames. Since I finished my carbon frame, I was thinking about using bamboo for my second frame. Later on, I found an article describing a bamboo frame Craig Calfee built for himself a few years ago. At that moment I was fully determined to build it too.

The most difficult part of building the frame was to find quality bamboo rods. It took me much more time than the building itself. I visited several dealers in near surroundings and I tried to find appropriate rods of the necessary diameters from huge amount of bamboo. Finally I found a few rods I wanted, but frankly said, next time I build such a frame, I'll rather grow my own bamboo or fly to Asia for it. The rods for the top tube, down tube and seat tube are some Chinese species of bamboo; I was not very satisfied with the quality of the surface, which was rather scratched (maybe it was from some downfallen scaffolding) and there were also a few woodworm holes in it (what if such beetles later devoured my frame?). The rods I selected for the seat and chain stay are some other species from Malaysia. I found also the appropriate thick-walled rods of another species for the seat stay. During breaking tests of these bamboo rods I found out that when I filled the inside with the polyurethane foam (which added only few gram of weight), the rigidity increased mainly of the rods for the seat and chain stay, which are the most critical parts of this frame.

The frame building itself was quite quick. I used the frame jig I made for my previous carbon frame. Bamboo rods were fitted in miter joints together with duralumin tubes (bottom bracket shell, head and short seat tube) and bonded with epoxy. The junctions in the rear part of the frame I made from polyurethane and the following laminating process of the joints with epoxy resin and woven carbon cloth was practically the same as for the carbon frame. Duralumin cable stops and brake bosses were made with water jet cutting and bonded to the carbon joints and secured with small screws. Finally the entire surface was covered with clear epoxy varnish.

The overall weight is 1860 g (4.1 lbs). It's a little bit heavier, but I expected it. I made also one piece of my carbon saddle with the bamboo post, which was in the upper part (in the place of connecting with the adjustable saddle support) strengthened with the carbon composite.

In this picture you can see the bamboo frame together with the bamboo post and the carbon saddle.

And here you can see my bamboo bike - the overall weight is 10.7 kg (23.6 lbs).

Update July 2005: Riding impressions - after one year

When I built this bamboo frame, I was interested in how would it differ from my carbon frame. Above all I expected that thanks to the unique properties of bamboo, as a natural composite, the frame would be more able to absorb road shocks and the ride would be more comfortable.

Now, after one year, I can write that the bamboo frame fulfilled all my expectations. The frame is excellent and still okay. Compared with the carbon frame it really does dampen vibrations better and the ride is more comfortable. I haven't had the feelings that the rear triangle would be very flexible, but to specify the flexibilty I would like to make the frame deflection test to compare the bamboo and carbon frame with other MTB frames, like Damon Rinard did for road frames (Frame Deflection Test).

I must admit there was just one thing I had to repair. I found after one ride in May that the aluminum brake bosses at the seat stay, which were bonded to the carbon rings and secured with screws, became slightly loose. I think I underdesigned this part. So, instead I made brand new carbon composite brake bosses, which now should withstand stress during braking. And besides, just to be sure I installed the carbon composite brakebooster that I made in the past to relieve the bamboo rods of the seat stay of stress. You can see the repaired brake bosses in the picture.

The connections of the bamboo rods with the carbon joints are still rigid without any problems. I know I can expect the bamboo to shrink or split sooner or later, but I hope that thanks to the used method of securing the mutual connection between the bamboo rods and carbon joints it should not loosen in the case of shrinking and the splitting of bamboo can be easily repaired.

I didn't heed advice that I should ride more carefully with this frame. But frankly, I still have some subconscious reactions to hear every unusual sound after strong bumps and inspect the frame after each ride. Maybe I should have more trust in the bamboo. Nevertheless, I enjoy riding this bamboo bike more than the carbon one...

Update August 2006: - still without any problems...

Update August 2007: - The bamboo bike after Dubnicky maraton 2007. More pictures from this event you can find here.

Some interesting bamboo links:

© Brano Meres