Status - 2013/12/7
The trike is on hold AGAIN. I had it working for a few months here in PDX and quite enjoyed it, but the square tubing supporting the seat base wasn't strong enough. Building a seat that fits this trike is tricky and I don't have access to a welder right now, so it is parked until further notice. I've also concluded that the design, while intriguing and fun, isn't too practical - the number of moving parts is too high and it doesn't fold small enough. I hope to build a simpler folding Python in the next year. There are more pictures at the bottom, and there's a video of it in action (pre-paint) at http://www.youtube.com/watch?v=JMBSBUDZiv8&feature=results_video

Background
I owe a lot to other sources for this design. Here are a few:
  • The Vacuum Velocipede, a tilting trike that was far ahead of it's time. Built by Dave Berkstresser, an ingenious bicycle enginner about whom I hope to write more later. Tim Hicks probably offers the best page of information on the VV.
  • Tim Hicks built his own Python Tilting Delta. I hope I enjoy mine more than he enjoyed his, though!
  • Of course, the Python Lowracer designed and initially built by Jürgen Mages.
  • Bram Smit's FastFWD tilting trikes provide the general inspiration for the tilt geometry.
  • The Jetrike is one of the first bikes I know of to use a front-wheel-drive moving-bottom-bracket (FWD MBB) design on a tilting trike, and I've tried (but probably failed) to use some of his calculations for a self-centering tilt geometry. His "Prior Art" page is an excellent list of resources.
  • There's more, I'm sure, but that covers some main points.

2012/8/3

I've been working on this for a few weeks and finally got around to taking pictures last night. Please forgive the poor image quality and lack of light - for some reason I never remeber to take photos during the day. There are more pictures in the Picasa album.


Left = Front. It's a delta trike. It's a tilting trike. It's a folding trike (more on that later). This is the frame as of last night. I'm now working on the seat so I can get a sense of fit before finalizing everything.
Front end is fairly normal Python geometry. Uses old frames and fork. Built around a 20" wheel. The "top tube" of the front subframe tapers from a seat tube to a 1 1/8" tube to a 1" steer tube, which fits conveniently into the stem.
Yes, that "top tube" really is asymmetrical. I hope it doesn't harm the handling too much, but it's necessary to make the folding work.

Front subframe folds under the main tube, hence the asymmetrical top tube - having it centered (or mirrored on the other side) would prevent it from folding completely.

Right now the trike is only partially folded, since I haven't rebuilt the suspension/tilt widget in such a way that the rear wheels can swing forward as they ultimately will.

Each rear wheel is supported by a "fork" with an independent headset, built onto a 1 1/8" OD tube salvaged from an old frame. Between the two, with a small amount of "elastomer suspension" (read: "rolled up old tube"), is the pivoting widget that keeps the tilt synchronized. Tie rods connect it to each fork.

2012/8/22
Did a rough assembly. The fit is good, but the seat angle is too low. I'm going to try rebuilding the seat stays with crutch parts. Then it'll be time to make the folding work and set up a tilt lock.

2012/11/28 - from Nelson, New Zealand
I pretty much finished the trike, but didn't get it all sorted in time to bring along on the trip to NZ. It is still sitting in a garage in California, awaiting my return - which may be a while. Here are some photos of the final frame, painted and assembled. The main thing still to be done is the fabrication of tubular aluminum seat stays to replace the angle stock. I have some crutch bits all ready to go, but didn't have time to make plugs for the ends and drill out the mounting holes.
Behind the trike is a trailer that I threw together for the purpose of getting rid of stuff - taking things to the various free piles around Davis. I ended up giving the trailer to a couple that was new to town and eager to get into a bike-based lifestyle. It's not the best trailer, but I hope it will serve them well for a while, at least.
Anyway, that's the current state of the Python Tilting Trike. Meanwhile, Vi Vuong has been posting progress on his ingenious variant to the Python mailing list. Have a look at the video if you get a chance: http://youtu.be/0XUXBtgQ9KQ