Python

It is based on the python invented by Jürgen Mages, a center-steered low racer.

I wrote a program to try to see if it could be self-stable. It isn't. It is written in the computer language Python.

Links:
Jürgen Mages page
The discussion list
Dirk Bonne - 20" low python

Jürgen's list of python links: http://www.python-lowracer.de/links.html

Electrified. 250W motor ~ 25km/h flat cruise.
From wildernessenergy.com

On the Mission Beach boardwalk

under construction

close-up of the pivot

after first test ride (note the handlebars - now removed)

more practice

even more practice

measuring the change needed

frame cut to new size

rear view mis-alignment after tack weld

finished, new geometry!
109cm wheelbase
40cm seat ht
47.5 BB ht
28.5cm trail

functionally complete

close-up of the BB and tube joints

close-up of the pivot and brake mounting

My experiences and recommendations for to others starting out:
(much of this is an echo of other's postings on the mail list)
http://www.freelists.org/archives/python/

• Have the seat as high as you can while able to touch ground, I actually
  found that I didn't start with my hands down, but it is helpful many times
• Do not use a low pivot angle, at least at first. The biggest thing against
  me was the slow response of steer. When I had a 59deg. angle and lower seat I
  could _not_ learn to ride it. It seems acceptable at ~65 now.
• Wear gloves. No need for a helmet, your hands, elbows and knees will always
  hit first.
• Find a wide space. I crashed and stopped pointlessly, and often, in the
  street. I even considered training wheels <gasp>. But, I moved to a set of
  tennis courts nearby and was riding around them in 10 minutes.
• I think my solid, stiff seat helps as it gives something stable to push
  against with the back to pedal and maneuver.
• I use the under-seat handlebars I just welded on, a lot, - but many don't
  and Jurgen apparently has control issues with them. I try to learn legs-only as
  I can. (You know, I gives me the impression of riding my Trek no-hands while
  standing up with the top tube between my legs, Tricky, but do-able.) I removed
  the high bars in the one photo; although the motion is less contrary to the hip
  motion. With the low bars I definitely feel pushing on the right hinders my
  hips swinging right when turning left.
• Starting took me more practice than maneuvering once going.
  I start by holding the brake, both hands on the bars, setting one pedal towards
  me and one good push to start. I need to get up 8+km/h to feel steady. The most
  important thing is starting very nearly upright and straight. A few quick
  adjustments until you get up more speed might be all you need. Again, because
  of the pivot angle I sometimes find the need to swing the wheel wildly if I
  don't start well; this is where the bars help I think, as the feet are not yet
  cycling quickly and the need to get the bike back under me quickly is large.
  Going downhill I keep the rear (the only) brake dragging, it feels more stable
  and prevents disasters.
  I have the chain set on the middle 36 ring and the middle 22 cog. I'll add
  shifters next week. A lower gear helps a lot too, it gets the feet moving
  around quicker. I find the same riding upright no-hands; it's easier to do
  while pedaling.
• I look ahead about 10 meters; anything closer, it's too late anyway...
  I can just turn around (usually) in one-half of a tennis court. Staying upright
  with the CoG over the wheelbase is many times more finicky than my Trek.
  The pencil vs. broomstick balancing
  analogy is apt, and looking ahead vs. at the front wheel really make a
  difference at this point.