[python] Re: [python]

  • From: "dirk@xxxxxxxxxx" <dirk@xxxxxxxxxx>
  • To: python@xxxxxxxxxxxxx
  • Date: Fri, 20 Aug 2010 11:46:13 +0200 (CEST)


Howard Stevens <hstevens94@xxxxxxxxx> hat am 20. August 2010 um 09:18

> Hey Dirk!
> I made some modifications and it was most interesting. First I reduced the
> pivot angle to about 55degrees which reduced the PSI considerably and
> improved the ease of turning. Then I reduced it further to 50 degrees and
> the PSI ceased altogether! Hooray!! Also the steering was even easier and
> the wheel tilting was moderate...I would hardly call it wheel-flop at all.
> This is not what I expected...I thought that the less the pivot angle, the
> more difficult the steering would be, but it was easier! So it seems you
> have solved my problem! I think the geometry and mathematics of all this is
> not simple, for many factors come into play, and to varying extents on
> different cycles. As you said, the pivot angle was quite significant and so
> is the position of the pivot. I also suspect that the Cof G of the
> bike/trike is also important as the percentage of the total load on the
> front wheel and pivot would also affect the centreing forces and therefore
> the PSI. Perhaps bicycles and triicycles also behave differently...does
> anyone have any ideas on this?. I have about 35% of the weight on the front
> wheel and that seems ok even on steep ascents, but of course on gravel a
> steep ascent will lead to wheel slipping. I haven't found much problem with
> loading the trike, and suspect that it would make no difference at all, if
> it is placed directly over the rear axle.
hmmm. in that case, the lower angle combined with the different pivot placement
maybe means that the pivot axis meets your body roughly at the same place like
the normal configuration?

> In my particular case it seems that it was necessary to decrease the pivot
> angle to counteract the PSI induced by the forward position of the pivot.
> Perhaps it also counteracted a PSI tendency because only 35% of the weight
> is on the front wheel. Another possible factor could be the amount of
> negative trail with different pivot angles and wheel sizes. It is starting
> to sound a bit like rocket science!!!
> Cheers Howard
changing one thing changes everything. there is no perfect world, just a sweet
spot somewhere :-)

> Hi M Channon or is it McHannon!  Yes, your python pivot is pretty much where
> mine is, so it is interesting that you don't get PSI.  I'm not sure what PIS
> is....your not taking the piss outa me are you?  Cheers Howard
PSI (pedal steering interference) = PIS (pedal induce steering)
at some point we had a discussion about which of the two sounded better. we
agreed onto this:
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