Check it out! Wheels!

There's a red support post holding it up, because the wheels aren't attached yet. Attaching the wheels is going to be a delicate operation to keep everything lined up and balanced, but here is the trike (less the seat), it's first real appearance.

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!

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.

Progress

As you can see in the photo below I have added the supports for the third pole so I will have a strong, triple poled frame. I built these braces a little differently than the first, as you can see from the close-up below.
I cut each brace pole on a 30deg angle, and drilled their mortises at a similar angle around the main poles, so that they meet in the middle snuggly. Only one of them required any real trimming to make snug. Then I make three oval holes in the third pole, set it down over these braces, and secure with a single pin through both braces. This oval hole is on the large side. To keep it from getting too large, and weakening the pole, I notched the peak of the braces.

It all worked very nicely. I don't have pictures of the main frame assembled, yet, but it is almost done. Next will come building the support for the front wheels.

The frame is started!

I have constructed the first piece of the frame!

This is the two lower poles that for the main part of the frame, which will make a triangle-beam with a third pole. The 1" bamboo poles are joined by short lengths of 1/2" bamboo, mortised and pinned, as shown in this photo:

The wire is 18 gauge galvanized steel I wrapped around the bamboo to prevent/repair splitting when the snug crosspole is inserted (an issue). The pin is a 3/16" hardwood dowel that prevents the crosspole from coming out.

This entire construction has nothing to do with my plans, and indeed contradicts advice I gave elsewhere: a speedbore can be used successfully on bamboo, if the bamboo is prevented from vibrating with a firm parrallel clamp. I decided to go with this joinery option, thinking that I would use several half-inch bamboos for triangulation anyway. Other sites described this sort of motising as a strong joint, and it appeared to be the simplest and least fussy option. Here I go!

The Model

I said I had made a model. Here are the photos. Note that I made a number of changes to the design after making this model. Which I will note after the pictures:

The most significant change I made was to invert the triangle formed by my three poles. That is to say, I put one pole on top and two along the bottom. Why?

It's hard to see in this photo, but the rear axle is at a noteworthy angle from perpendicular. Because there is no continuous bar from the main frame to the axle, there is a large amount of play, and a slight inaccuracy in the length of the poles or squareness of the joints easily become noticable errors in alignment. By using two poles along the bottom, these become straight by definition, and the number of variables is reduced.