[python] Re: A Bicycle Can Be Self-Stable Without Gyroscopic or Caster Effects
- From: Vi Vuong <vi_vuong@xxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Fri, 15 Apr 2011 22:32:55 -0700 (PDT)
Hi Pascal,
Youtube user b100Saa has done some study on self-centering effect with various
weights,
http://www.youtube.com/user/B100
Maybe someone here knows him personally.
Their model bike is most similar to low/midracer recumbent with fixed boom. On
a python moving "boom", the weight on pivot would to be much greater than the
BB
assembly to self-steer. However, we can leave out the top-heavy BB to make it
easy to illustrate the self-centering effect. I can build a miniature model
small enough to roll down slope driveway if you are willing to start a python
paper as a group effort. With realistic bike + rider, I think the subject of
hands-free riding (freedom) is worth pursuing...
Vi
________________________________
From: "pybuen@xxxxxxxxx" <pybuen@xxxxxxxxx>
To: python@xxxxxxxxxxxxx
Sent: Fri, April 15, 2011 7:01:28 AM
Subject: [python] Re: A Bicycle Can Be Self-Stable Without Gyroscopic or Caster
Effects
Good spotting, Christian, thanks for the news. One of the co-authors, A. L
Schwab, usually provides his publications on his website (you are usually
allowed to - depends on the journals though, not sure with Science). This one
is
brand new (from today), so it's not yet there, but might appear soon:
http://bicycle.tudelft.nl/schwab/Publications/papers.htm
Ok, I just saw somebody posted a link with the article, so now you'll be able
to
grab it.
Anyway, most of the material can prob. be found in other articles of his
(recycling is common...) that you might also be interested in, I have recently
commented on one of those a some weeks ago:
//www.freelists.org/post/python/Cool-handlebar-for-48deg-20in,16
The videos on the link by Marek say it all anyway. I also agree with Jürgen's
feel.
Gyroscopic effect is known since the 70s to not contribute significantly to
stability (Jones). Not so sure about the Caster effect for _riderless_ bike,
that part may be new. Has anybody tried to launch their python at various
speeds, e.g. down a hill? Maybe you would have been writing a "Science" paper
if
you had :) Note: load it up with sandsacks before trying...(self-centering
effect). The riderless feature is just about control: the tendency of the bike
is to recover from a potential fall by self-steering. Not sure how a Python
bike
would behave. Anyone to volunteer?
Pascal
On Fri, 15 Apr 2011, Jürgen Mages wrote:
> 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 Effects
>>
>> 1. J. D. G. Kooijman1, 2. J. P. Meijaard2, 3. Jim M. Papadopoulos3, 4. Andy
>>Ruina4,*, and 5. A. L. Schwab1
>>
>> Abstract
>>
>> 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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