[python] Re: Lean Steer Python/Hipparion Trike

  • From: George Durbridge <gdurbrid@xxxxxxxxxxxxxx>
  • To: python@xxxxxxxxxxxxx
  • Date: Fri, 05 Jan 2007 13:12:41 +1100


I am still coming to grips with your design, which is extraordinarily
interesting and has a lot of good points, but I have three queries
already.  Have you, btw, seen Paul Sims' and Bob Horn's leaning trike
designs?  If not, I will try to find links.

First, if the rocker and swing arms need ends as strong as the 5mm plate
lugs you specify, and on Dirk's comments they well may, is it really
suitable to weld the lugs onto 1.5mm plate endcaps?  It will be a
difficult weld, and even with a good weld the lug will be prone to tear
out of the endcap.  Why not make the tube element of each arm 30mm
longer at each end and let in a transverse tube to take the bolt, like
your rear axle arrangement?

Second, is it possible to achieve both self-restoring geometry (i.e. the
centre of gravity is raised by leaning) and enhanced cornering by
leaning (i.e. the CoG is lowered by leaning) in one design?  I
appreciate that when the trike leans the rider rises relative to the
frame, and the frame sinks relative to the ground, but at any one angle,
surely one of those effects has to prevail, giving an overall reduction
of CoG height (better cornering, but no restoring action) or an overall
increase of CoG height (other way about).

Third, does the CoG move outward as the trike leans?  That is, does the
CoG move horizontally toward the outside of the corner, in addition to
any vertical movement?  In the photo of the earlier design, it looks as
if it does, and any self-restoring lean mechanism I have come up with
has the same effect.  It is an effect I would try to avoid, as the limit
on ground loops is the angle with the horizontal made by a line from the
CoG to the contact patch of the outer wheel: the lower this angle the
better, but the angle increases as the CoG moves horizontally outwards.

George Durbridge
+61 3 9481 3500
+61 409 413 945


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