[python] Re: A Bicycle Can Be Self-Stable Without Gyroscopic or Caster Effects
- From: "dirk@xxxxxxxxxx" <dirk@xxxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Mon, 18 Apr 2011 07:59:39 +0200 (CEST)
no, actually, its a design loop! devote yourself over and over to the same
variables and you'll always find something new :-)
- DirkS
"Jürgen Mages" <jmages@xxxxxx> hat am 17. April 2011 um 20:24 geschrieben:
> Help me - I am trapped in a time loop ...
>
> Jürgen.
>
>
> On 17.04.2011 20:04, Vi Vuong wrote:
> > Hi Ray,
> >
> > Thanks for sharing the program. Is there a way to automatically grind
> > through
> > the 18 parameter space, and save the output? I think we need to find stable
> > speed between 4-8mph to run along with the experimental bike. The console
> > output
> > velo A B C D E #6 #7
> > m/k 10**8 10**9 10**9 10**9 10**10 10**20 10**26
> > suggests that when colunm #6 and #7 both go positive then we have stability,
> > and
> > can be used to search the parameter space.
> >
> > Vi
> >
> >
> >
> > ________________________________
> > From: RayS <rays@xxxxxxxxxxxxx>
> > To: python@xxxxxxxxxxxxx
> > Sent: Sun, April 17, 2011 8:01:36 AM
> > Subject: [python] Re: A Bicycle Can Be Self-Stable Without Gyroscopic or
> > Caster
> > Effects
> >
> > Interesting thread - the self-stability program I wrote
> > http://rjs.org/Python/FrameGeometry.zip
> > shows the effect the researchers wrote of pretty clearly. It does also have
> > input for rim/tire mass (mouse over the boxes for explanation).
> > If a python's:
> > - front mass is at least 45cm in front of the pivot line
> > - rear mass is <24cm to rear axle
> > - trail <11cm
> > -wheel mass is low
> > it is nearly neutral.
> > All these things have been covered on the list one way or another, except
> > wheel
> > mass.
> > Panniers off the back, shifting weight backward, reduces self-centering
> > force on
> > the pivot.
> > Weight in the very front can increase some desired flop, but is a sensitive
> > factor and makes slow riding more tiresome.
> > Trail should generally be minimized.
> > Importantly, the dynamics are very sensitive to wheel mass; heavy wheels,
> > especially the front, eliminate any chance of stability! If you think about
> > it,
> > gyroscopic effect prevents the front wheel from responding to lean, which is
> > what gives bikes stability; it actually turns the forks the opposite way
> > when
> > leaned.
> >
> > Remember all this has to do with self-stability, and not necessarily how a
> > python "feels" to ride using leg steer. Note that in the attached I set the
> > pivot torsional K to -7; a small opposite force like your hips make when
> > riding
> > the python which counters the self-center effect. It then has a wide range
> > of
> > stable speed. The further mass is from the rear axle the more -K is
> > required,
> > and the lower it is the less stable.
> >
> > It would also be interesting to let the code grind through all reasonable
> > combinations of the 18 variables used and see where the islands of stability
> > are.
> >
> > Ray
>
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