Bamboo Bike Frame.

Step 6 Reinforcing the Joints

This is the single messiest thing I have ever done, and also has probably contributed the most to my future cancer. Wear gloves, and wear a mask.

Masking comes first. If you haven't spread newspaper or cardboard all over your workspace yet, do so now. Use several layers of newspaper - this stuff soaks pretty well. Also, mask off the parts of your frame you don't want to have to scrape epoxy off of afterward.

If you've got vacuum bagging equipment, use that instead of this method I'm about to describe.

1. Cut up some strips of polyethylene (trash bags) and keep them handy.

2. Then get your reinforcement of choice (I chose hemp fiber) and break it into manageable chunks.

3. Mix your epoxy resin and hardener according to the instructions.

4. Soak the reinforcement in the epoxy, squeeze out excess resin, and plop it on your joint. Wrap it around and reinforce what needs to be reinforced.

5. Take the polyethylene strips and wrap them tightly around your reinforcement, so that you can squeeze out more excess resin. This will also help keep the surface fairly uniform.

6. Wait. Before the resin sets, but after it's no longer very sticky, take off the polyethylene.

7. Wait.

8. Repeat 1-7 until you are satisfied with the amount of material reinforcing your joints.

Comments

[rhysc]

I just did one using twine and got very neat and strong results. Basically just bathed the twine in fiberglass and wrapped it around the joints.

[rorymcstay]

 Hi, first off this instructional inspired me, im now starting to build one. but i have just one question for you. how did you get the bottom bracket shell in. did you use a glue/resin? thanks. ill be using carbon tow (string)

[huntjulien]

im thinking that you might have had a nice stronger finish if you had used a bit more epoxy that sanded it down a little so it is nice and smooth then if you want you have have added a varnish of some sort

[adie.mitchell]

the resin in a composite material has no strengthening properties on its own. extra resin is just extra weight(though you dont want to starve the fibers of resin). you can sand, but sanding any further than the surface of the fibers, weakens the joint because the strength of these composites comes from the long fibers. if you sand into the fibers, you shorten them.

[godspiral]

"get your reinforcement of choice (I chose hemp fiber) and break it into manageable chunks." did you consider just taking a spool of hemp, making an initial knot, and keep winding tight, and brushing on epoxy as you went? I assume you used a whole spool of thread for the bike (do you know weight of hemp), and I assume that its much easier to work with than fiber/carbon sheets?

[adie.mitchell]

people use spools of carbon threads, but not cloth, as far as i know

[toddheist]

electrical tape sticky side out also works to hold and compress the hemp/epoxy resin :)

[xman]

So I hear. But e-tape is so precious, and trash bags so much less so!