Thanks Christian. The clue is: if the rear part's center of gravity is shifted far enough over the front part, then the negative trail bike is inherently stable.
Cheers, Jürgen. On 15.04.2011 12:11, Christian Andersen wrote:
Hi folks In Science there is an article about bikes, that could be interesting for those of you guys, who have sufficient knowledge (unlike me). Maybe it is worth to have a look at to improve the pythonconcept regarding stability. http://www.sciencemag.org/content/332/6027/339.abstract Science 15 April 2011: Vol. 332 no. 6027 pp. 339-342 DOI: 10.1126/science.1201959 * Report A Bicycle Can Be Self-Stable Without Gyroscopic or Caster Effects1. J. D. G. Kooijman1, 2. J. P. Meijaard2, 3. Jim M. Papadopoulos3, 4. Andy Ruina4,*, and 5. A. L. Schwab1Abstract A riderless bicycle can automatically steer itself so as to recover from falls. The common view is that this self-steering is caused by gyroscopic precession of the front wheel, or by the wheel contact trailing like a caster behind the steer axis. We show that neither effect is necessary for self-stability. Using linearized stability calculations as a guide, we built a bicycle with extra counter-rotating wheels (canceling the wheel spin angular momentum) and with its front-wheel ground-contact forward of the steer axis (making the trailing distance negative). When laterally disturbed from rolling straight, this bicycle automatically recovers to upright travel. Our results show that various design variables, like the front mass location and the steer axis tilt, contribute to stability in complex interacting ways. greez, christian a wannabe pythonrider
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