[python] Re: Handlebars mounted
- From: Ray Schümacher <mtb@xxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Fri, 08 Apr 2005 07:41:31 -0700
At 12:07 PM 4/8/2005 +0200, you wrote:
>Last week I mounted handlebars to PX.5 just for the fun of it.
>But I cannot use them. As soon as I touch them, my riding gets
>out of control.
I wonder if your arms and legs have opposite demands on your torso; to turn
hips/legs right, you must twist torso left against the seat, but if you pull
back on the right bar it tends to twist your shoulders right as well. I wonder
if you installed reverse-action steering...
>But like everything, this is a matter of experience and when Dirk
>reports about how helpful his handlebars are I believe him.
I notice that Dirk has the most relaxed (60deg) angle and less trail than any
other in the survey, 14cm.
Although the low angle maximizes seat rise for self-centering, it also
increases wheel flop (the moment/energy the front mass has falling to the side)
which counters the centering, as well as reducing the sensitivity of steer.
(They also have different inputs, the self-center is constant due to weight and
geometry, the flop varies with speed (v) because part of that force is the
centrifugal turn force on the front mass. Note also that the trail effect on
stability increases with v**2, so in an normal positive trail bike its effect
rises rapidly from 0 and becomes stable about 10Km/h; in a python, the frame
starts out over-stable at 0 and eventually goes unstable at speed from the
negative trail*v**2.)
His minimum trail also reduces the self centering, so would require less hand
force to push (and might make it less un-stable at speed).
I had a good plan for some new software to help with this, but no time, yet.
>Also the python handlebars have to be very strong to counter the
>self centering force. With mine I hardly could turn the front part
>while standing and with feets off the pedals. As the handlebars
>additionally increase the air drag they won´t be an option for me.
How about aero bars? ;-)
>PS:
>At the beginning of this week I made a 3 days tour with P3 into
>the hilly area north of my hometown. I carried 15 kg of baggage
>and was positively surprised about the handling, especially
>uphill.
NIce. My free time has dropped this month, with work projects and tax time. I
did cut all of the pieces for my bike, but no welding yet; I'm planning ~60deg
angle with ~20cm trail. The suspension is unclear, but I need it for the crappy
roads here - with budget cuts and deficits US roads are getting worse all of
the time. A beautiful day here to commute, though.
Ray
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