Splicing in the crank supports

This is a close-up of the joint for the crank support poles. The one that joins to the lower pole is cut on the angle and butted together. A slot is cut in both poles, sufficient to accept a 3/16" ply, which is carefully cut to the precise angle required, making a long, skinny triangle. Epoxy is applied to the edges of the slot and the butt joint, it is assembled and bolted near the joint. A wooden pin (not shown) will be inserted near the points of the triangle. The wire wrapping is to prevent the bamboo from splitting at the cut.

If I do it again, I will cut a slot through both sides of each pole, and have the triangle pass all the way through. As it is, the ply can wiggle slightly inside the poles, and depends on the epoxy to prevent this.

The upper bracing pole is cut on a very careful angle (took me several tries to perfect), and rounded out a bit with the dremel for a firm fit. I also cut into the pole it connects to, so that it can butt up against a solid edge, but not so far as to open the cavity of the pole. I single bolt holds it very firmly, although I will probably add epoxy as an additional measure.

My God! It actually looks like something

Top View

I know it's a little hard to see, with the stray bamboo pieces, and the 2x3 support the tail. It was hard to get a good view on it in the basement. But you can see the rear wheel fork and the crank in place.

Rear Wheel Fork

You can see here the bolts into the bottom side of the rear fork, that connects it to the hardwood dowel that is bolted to the bamboo. The gray line on the steel is epoxy that seals a cut I made when I though I could get the bamboo itself into the steel. Dumb idea. There's a half-circle cut-out in the top bamboo pole that should keep the rear side of the fork from shifting fore-and-aft, and a bolt that holds the fork firmly into the cut-out.

Crank

Not finished yet, there'll be a second support pole connecting to the second top pole of the frame, but here you can see the plan. The crank is sandwiched between curved cut-outs. The support poles cross, and when the last support pole is added I will pin them together, which will prevent them from spreading and releasing the crank. That and a generous amount of epoxy.

The crank is heavy, and reminds me how much weight I am saving using bamboo. I think the crank weighs more than all the bamboo in the frame!

Crank

I cut the crank off of a mountain bike. I now have a cylinder with little metal tube remains pointing in three directions. My plan is to secure it between three short poles with a joint known as a "bird beak," where the poles cross and pinch the cylinder between them. Excellent idea, but execution is difficult, since the poles need to be positioned with some tension. I've tanken the first step:

I cut two slots in one of the poles, that precisely correspond to the edges of the widest tube. Then I epoxied the crank onto the pole. Next I'll attach this pole, then add the others. The epoxy will allow the "unpinched" crank to hang in the air from just one pole.

Metal-bamboo joints

Well, I've finally done it. I've joined bamboo to metal. Someday maybe I'll tell the story of my adventures trying to drill hardened steel, and how I wound up with three 3/16" drill bits. But I slid one end of a 5/8" dowel into a bamboo pole, and the other into the tube of the bike, where it fit snuggly. Drilled twice through both ends. Took it apart, smeared the dowel with JB Weld (epoxy), put it back together and bolted it fast. It's permanently joined, now.

What I actually connected was the rear half of the rear bike triangle with the support poles.

Third Pole Photos

Below I talk about how I added the third pole by making a triangle and insterting the point into a mortise in the third pole. Here are pictures.

hacksaw vindicated

I tore apart another hacksaw blade. But, being the try-it-and-see sort of guy I am, I tried a third. A different hacksaw blade. And wouldn't you know, the problem was the cheap-a** blade that came with my cheap-a** saw. I've made three cuts with a better quality blade and no sign of dulling.