• From: Howard Stevens <hstevens94@xxxxxxxxx>
  • To: python@xxxxxxxxxxxxx
  • Date: Fri, 20 Aug 2010 02:18:13 -0500

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.

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

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

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