[python] Re: Python Stability Continued
- From: Dirk Bonné <dirk.bonne@xxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Sat, 30 Jun 2012 22:11:49 +0200
On 30.06.2012 09:40, Peter Clouston wrote:
> Thank you all for your replies. I am a bit surprised at comments that
> the python is easy to ride however. Jurgen's account of learning to
> ride hardly suggests that. Nor do the reports by several builders that
> they have been unable to learn to ride their creations. Several of
> them have given up and gone to trike conversions as a result. I think
> that with its other advantages and general coolness the Python would
> be a real hit if it was a bit easier to ride.
That is true, but that is like asking a python not to be a python.
I think that the importance of hands-free stability is overrated. I
furthermore think that instability of the python is overrated too. The
real trouble is that the python-rider feedback loop is changed in both
ways (compared to an upright) and that needs to be learned. In addition
the python is beginner unfriendly because leg-steer is inferior to
arm-steer because of the mass that needs to be moved. That prevents the
beginner to wiggle the steer (like I see my son do on an upright) to
compensate his lack of skill.
>
> A bike that requires active action by the rider to keep straight and
> upright is ridable, but not stable, by my definition at least.
An upright bike is hands-free stable. That is only true if the person on
the bike is holding still and the bike is propelled. Like you describe:
freewheeling and down hill. If you put a person who cannot ride a bike
on a bike, the self-stability is gone.
If you ride a python and your feet slip the pedals, the bike will begin
move away from the trajectory. That is the amount of instability we are
talking about. The python does not need any more input than other
recumbents. For example when I ride together with other bents, I can see
that my front wheel wiggles much less than front wheels on regular
recumbents (they seem to be compensating disturbances when pedaling).
> Nor by the definition of vehicle design engineers. A problem with
> requiring continuous rider input just to keep upright is that as
> speeds increase, things happen far too fast for the rider to react in
> time. In fact, the rider's delayed action may in fact make things
> worse in the case of oscillating instability. This is known as "pilot
> induced instability" in aviation.
That sounds like a very subjective concept...
At high speed the input needed to correct the bike is very little. The
leg mass doesn't matter anymore. The question would be when "pilot
induced instability" happens for a python. I habitually ride 55kmh (as
this is on a certain slope on the way into Town), never noticed anything
odd while riding. My maximum speed is 66kmh and that has only been
limited by prudence instead of ride/python stability.
There are other examples of even higher speeds (95kmh) on the list. As
far as I am concerned that is enough ;-)
There is (in my view) a very large myth on this list about the (very
small) high speed stability of the python. I think it has a lot to do
with personal perception of what is safe and not what really happens on
the bike when one is going fast.
Dirk
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