[python] Re: Jetstream

I was curious as to the feasableity of riding a 20"lowracer on a local bike trail and occasionly on a well marked bike path on a city street.of course considering how to balence taken into consideration. ----- Original Message ----- From: "Ralph Essinger" <ressinger@xxxxxxx> 
To: <python@xxxxxxxxxxxxx>
Sent: Wednesday, March 14, 2007 10:39 AM
Subject: [python] Re: Jetstream



What happened? Where did everyone go? I'm finally on holiday gearing up
to finally build my first python and the inspiring, whimsical teachings
and leanings contained in the mailing list have come to and abrupt halt?
Has it moved somewhere else? If anyone knows why it has all of a sudden
become very quite please let me know; it's kind of eerie.

Ralph

-----Original Message-----
From: python-bounce@xxxxxxxxxxxxx [mailto:python-bounce@xxxxxxxxxxxxx]
On Behalf Of dirk.bonne@xxxxxxx
Sent: March 2, 2007 5:23 AM
To: python@xxxxxxxxxxxxx
Subject: [python] Re: Jetstream


Stephan Schöling wrote:

It took over 1 hour to read that ;-)

May i try to summarize with easy words, please correct me if i'm
wrong.

The frame itself isn't stable, the frontpart flops sideway (by
gravity). The self-centering effect works against that, is making the
bike stable. If I put some weight to the seat (gravity too), i
increase the self-centering effect. My python frame (without rider)
balances at ca. 8 kg on the Seat. (Borderline between the two effects)

That depends on how exactly the borderline would be defined. At 8kgs,
there must be a turning angle at which the front part still flops.

For a useful definition of that borderline I see to possibilites:
* for a certain turning angle (e.g. 20 degrees), there is a balance
* or for any turning angle the wheel flop is smaller then the self
centering effect.

But it is a lot of work to come up with the correct numbers I guess. I
wonder if there is a simulation tool that would be able to calculate
this things.

The riders weight increases the self-centering effect.
The pivot angle decrease: increase wheel flop, increase self centering



(up to a point). (we still have to find the proportion) neg trail
increase: probably not much influence on wheel flop, increase self
centering.

Luggage placed near the rear wheel doesn't have much effect to the
stability of the bike, because its away from the SBB.

Dirk:
You wrote, your formulas are wrong ?
What is wrong with them ?

Qualitatively they are ok. But quantitative not. The real seat rise is
larger then the one calculated. This can be noticed readily. The reason
AFAIK is that in the models I simplified the tires by being infinitely
thin, and this does have a significant effect.

Dirk

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