[python] Re: python Digest V8 #63

  • From: Howard Stevens <hstevens94@xxxxxxxxx>
  • To: python@xxxxxxxxxxxxx
  • Date: Tue, 17 Aug 2010 05:55:11 -0500

Hi again Dirk,
I very much appreciate all your comments and experience in riding pythons
and flevos.....it is very useful to me because I am working alone here and
haven't met or contacted anyone in the locality.  I have made a couple of
prototypes... the first had a pivot angle of about 70 degrees and the
current one is at the 62 degrees that Jurgen recommends.  The 70 degree one
was rather twitchy but easy to turn, while the current one is more stable
with less PSI and a bit more difficult to turn.  So I would expect that by
reducing the angle closer to 45 degrees that it would be as you say and have
less PSI still, go like a train, have more difficulty turning and maybe
considerable wheel flop.  Did you notice wheel flop being a problem on the
Flevo?  As my vehicle is a trike do you think that could be less of a
problem at low speeds?  WHat exactly do you mean by having trouble fumbling
at takeoff and low speed?  Perhaps a compromise of say 55 degrees may be the
optimum for a trike, as I read somewhere that that was the theoretically
best angle for seat rising effect without too much wheel flop??  What do you
I went to a motorbike shop today and checked out their steering dampers and
I think you are right...they would be of no use for a trike, because they
are basically to smoothe out high frequency shudders and so would not be
effective for a low frequency PSI oscillation, unless they were adjusted to
be so strong that you really couldn't turn the thing!!  So why were they so
strongly recommended for the Hipparon trike?  Was it because the pivot angle
was so high that steering became very unstable without it?  It probably was
not for PSI in that case.  And yes, I can't see that the rubber cylinder
damper would be useful for anything but parking.

I feel a bit guilty tampering with such a successful design as the python
and can imagine that you don't have any noticeable PSI.  I have used 20 inch
wheels and the reason I am having some problems is because I haven't got the
pivot in the right place, it is about 150mm in front of the line of the
hips!! But I am limited by my desire to make the thing fold up into a box!!
The problems I am having are not great, as putting the handlebars on, as you
suggested has been a great improvement.  I just want to be sure to get it as
good as possible within these restrictions.  I think I won't be so radical
as to put it behind the seat especially as it didn't help the situation in
the PX5.  Maybe some other time!

Thanks again for your input, cheers  Howard

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