The python is a center-steered lowracer with 2x26" wheels, front wheel drive and rear suspension.
The ancestor of the python is the "airbike", another center-steered recumbent I have been riding since 1996 - and still enjoy to ride. Once you have learnt the steering principle, the bike can easily be handled without using your hands, therefore handlebars can be omitted.
However, any average mortal person can learn how to ride such a bike, it's just a matter of determination and patience, to different degrees. The latter usually is counted in days or weeks. After having gained full control over the machine (we are talking of months now), the ride on center-steered bikes is said to have a kind of metaphysical quality which more than rewards the candidate for all the pain and suffering he has gone through on his way towards perfection.
I took part in some races with the airbike and felt that I should have a faster bike. I decided to build a lowracer, but of course it had to be center-steered as well. The construction should be as simple as possible and the parts taken from normal MTBs. Homebuilding a lowracer for absolute beginners.
I began the CAD constructions in winter 2002/03 and in the same time built a prestudy bike, which I called "flairbike". The rear suspension and the seat construction of the flairbike work pretty well but I was not satisfied with the front part. Additionally the flairbike was not low enough for my purpose. The breakthrough was the idea of using a normal bottom bracket for the steering pivot. Thus the pivot has enough stability and the front part can be straight. As a bonus, the whole bike can be splitted in the middle simply by loosening the crank arms.
I started the building in february 2003 and the first roll out was only 2 weeks later, although I had to learn the MAG welding from zero. I did not spend more than 10 Euro for the material. And amazingly the bike looked pretty good. When thinking of the long and straight frame of this new kind of bike, it reminded me of some kind of huge snake. So the name "python" was chosen.
Some people asked me if the python is steerable at all because of its negative trail. In general, bikes with NT are not stable, especially at high velocities or when applying the front brake. But the steering geometry of the python is different, because the construction behaves like a "hanging pendulum". This means that the drivers weight forces the front part into a centered position, thus stabilizing the system.
Meanwhile I spent more than 2500 km on the python and I really love this bike. I use it daily for commuting, recreation and even in urban traffic. And still have many plans with it ...
Bent but not Broken --- Jürgen, June 2003
Now more than a half year has passed since the first roll-out. The mileage reaches the 5000 km mark and most of the python´s childhood diseases have been cured. I get a lot of encouragement and regards from people all over the planet, which is a great honour to me. In fact, I really think that I am into something here. Some have started to build their own version and to support them, I established a mailing list for home builders.
After removing the steering damper, the turning cycle is acceptable for me now (6 m). The bike runs smoothly in all situations and always stays controllable. Lately I reached 70 km/h downhill without feeling too unsafe [Remark: considering my later experiences I really doubt this value. 50 km/h seems more realistic to me. (Jürgen, August 2005)]. In offroad terrain the bike is easier to handle than any other recumbent I know.
The weight of the python P1 is 20.2 kg, fully equipped, which is too much. Initially I had planned to stay below 15 kg. A lot of weight can be saved with better components and thinner tubing. Another disadvantage is the small ground clearance of 7 cm. One solution would be the use of taper roller bearings for the steering pivot instead of the bottom bracket. Or leave the BB as it is and bend the lower crank upward.
Jürgen, October 2003
One year has passed since the roll-out of the first prototype. Last week, the second one had its maiden trip. The design has changed a bit in the middle part of the frame. By bending the lower crank upward the lowracer gains a lot of ground clearance, which is a big advantage, especially off-road. The rest of the bike has proofed to be good during 6000 km of daily usage. The pictures and reports of my own python experiences have convinced a lot of people to start their own building. I have started to abandon my airbike and insert its good components into my next python. Also I have plans to build a streamlined carbon fibre version of the python during this summer. Let´s see, how the story continues.
Jürgen, February 2004
Two years have passed since the first python experiments. Meanwhile I have more than 10.000 km of riding experience and recently I have finished the fourth prototype which I built for my daughter. My wife is riding the still existing and sane first prototype. P3 has become my all-time favorite bike. It weighs 19 kg fully equipped and suitable for everyday use. I use it almost daily for commuting and recreation. Slow pace offroad is as much fun as relaxed cruising with 25 km/h or speeding with 40 km/h on level ground. Uphill climbing works great, considering that the python is a front wheel driven bike. Coasting downhill with speeds from 50 km/h still scares me and needs more practice. My longest day trip was 160 km with light baggage.
A project survey in the mailing list shows about 15 known python-like building projects worldwide. Most of them are still in progress, and some of them have been abandoned. Unlike my hometown, where 3 python riders can be found, not a single other project seems to be successful so far. I assume that building problems are to a lesser extend the cause of these disappointments than the long-lasting learning process which was underestimated by the builders. So let me repeat this: it takes about 300 km to feel safe on the python and about 1000 km to use it with the full performance that it offers.
Jürgen, November 2004
Two years have passed since the roll-out of the first python prototype P1. The frame geometry, that once originated from a more or less random idea, did not change much since then. Pivot angles around 65 degrees and trails around 25 cm are dominating my succeeding projects as well as projects from others.
If one has a look at the major drawbacks of the python, low high speed (>50 km/h) stability and big turning circle (5 m), the question arises, if these could probably be overcome by a more optimized geometry. At the moment there are both mathematical as well as practical approaches to reach this goal. Ray Schumacher (USA) develops a program that calculates dynamic bike stability, Dirk Bonné (Denmark) calculated the pivot rising and I built an experimental prototype called PX, which will serve as a base frame for various ideas.
Jürgen, February 2005
Python riding experience is 15.000 km now. Recently I made a 900 km tour with the P3. It took me 4 days and it was very sweet (longest day trip was 240 km). Although I carried lots of baggage (30 kg) with me and the terrain was quite rough, the bike behaved flawlessly. The self centering effect was enhanced by the additional weight and so was the downhill stability. Coasting upto 55 km/h was possible without panic attacks. During the following trips without luggage I still felt this increased calmness when coasting fast - this is a good hint that fast coasting is not only a matter of frame geometry and weight distribution but also of training and self relaxation.
Considering the usability range of the python I would say that it is perfect for flat and undulating terrain. I would not recommend it for mountainous regions. Uphill climbing is great but you will have the limitations downhills.
I am highly pleased with the performance of the P3 so far and it is still my favorite bike. Weight (20 kg), turning circle (5 m) and limited coasting speed (50 km/h) are surely drawbacks, but the advantages are still impressive enough and I do enjoy every ride with this amazing machine.
Jürgen, August 2005
Python riding experience is 25.000 km now. The project has developed nicely and lots of new Pythons have been build in various countries. The mailinglist community has grown constantly to now 125 subscribers and is quite active. Lots of people are willing to share their experiences with the result that we are very close to a decent theory about the frame geometry and optimum configuration.
I am still riding the P3. The cartridge BB that I initially used for the steering pivot is still in service and shows no signs of wear yet. The rest of the frame, including the rear suspension, did also endure bravely my sometimes rough treatment. The only major modification was the swapping of the front V-brake from a place on top of the 40x10 tube to the bottom side of this tube. This enabled me the complete sealing of the front fender and it greatly improved the brake maintenance.
Jürgen, October 2006
