[python] Re: Position of Steering Pivot Axis

On Fri, 2006-01-06 at 23:41, Jürgen Mages wrote:
> Hello all,
> 
> after one of the most urgent questions in "python physics" has been
> solved last year ("What is the perfect steering pivot angle?"),
> I want to push the solution of another crucial issue:
> 
> "Does the pivot axis have to go through the middle between both
> hip joints in order to minimize pedalling/steering interferences (PSI)?"

Jurgen,

One factor must be the torque around the steering axis from pedalling. 
Assuming the pedalling force and the sideways displacement of the pedal
from the mid-axis of the bike are constant, this torque will be greater,
the shorter the distance along the bike from the steering pivot to the
pedals.  Bringing the pivot back to the rider's hips will tend to reduce
the torque, but putting the pivot behind the rider would reduce it even
further.

There are probably good ergonomic reasons to put the steering pivot
close to the rider's hips, so it may be that the practical minimum PSI
is achieved by the layout you mention.

One test of this theory will be Robert's machine, which has the shortest
distance between pivot and pedals of any you illustrate (or that I can
think of).  In my attempts to ride it, my main problem was trying to
balance, but pedal-steer didn't seem to be a problem.  I take your point
that I might have different preferences, once I can keep the machine
upright.

George

> To gather the infos I have set up a new site:
> http://www.python-lowracer.de/modifications.html
> Some pictures are already there.
> 
> Any ideas?
> 
> Cheers,
> Jürgen. 
> 
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