[python] Re: Jetstream

  • From: dirk.bonne@xxxxxxx
  • To: python@xxxxxxxxxxxxx
  • Date: Fri, 02 Mar 2007 14:22:57 +0100

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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