[python] Re: Bipolar - a double-pivot folding python
- From: Vi Vuong <vi_vuong@xxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Wed, 13 Apr 2011 19:41:05 -0700 (PDT)
Hi DirkB,
I did a quick sprint test at lunch in the parking lot ~10-13mph (16-20km/h),
faster than the μPython for sure, and couldn't feel much movements transferred
from the rear wheel to my back. However, I do get nervous at higher speed as
I
am still in training. Any upper-body movement would transfer directly to the
rear wheel, so this is a rider's issue, not the bike. At most, I can say that
the bike is not very tolerant to random body movements (inputs), and therefore
may be more difficult to ride at higher speed. I vaguely recall similar
description for RWS bikes.
In theory, the rear wheel has positive trail and seat rise effect (60deg
pivot)
to stabilize side motion, plus the pivot is practically locked by the upper
body's weight on the seat rest and tire friction, especially at low speed, good
enough for mobility as a folding bike. If high speed is the aim (downhill?), I
would go for a trike like nobuo has demonstrated. A triple-pivot folding trike?
Vi
________________________________
From: Dirk Bonné <dirk.bonne@xxxxxxx>
To: python@xxxxxxxxxxxxx
Sent: Wed, April 13, 2011 12:54:05 AM
Subject: [python] Re: Bipolar - a double-pivot folding python
Hi Vi
it would be very interesting to know if there is a wobble when riding high
speed.
regards,
yet another Dirk
On 12.04.2011 08:15, Vi Vuong wrote:
Hi Dirk,
>
>
>Yes, the rear pivot is somewhat redundant in terms of steering,
>and auxiliary at most (only during turns). However, it's primary
>purpose is to enable 2 folds for compactness, yet without any
>folding locking mechanism and seat removal like the commercial
>Grasshopper or Cobra or the μPython. I was prepared to make a
>pivot
>lock in case it's not ridable, but after some testing, it seems
>that
>I can skip the lock and consider the extra instability as a
>compromise / feature. Over the next few months, I will be
>comparing
>its mobility / utilization vs. the μPython, going
>different places. The μPython will probably win the popularity
>contest, with the tiny motorcycle tires alone.
>
>
>There is a steering linkage between the wheels, an organic one
>(the
>rider). I was surprised that the weight of my back is able to
>keep
>rear pivot / wheel pretty steady going straight without any
>
>correction effort, not much different than regular python. Some
>coroplast friction between the backrest and seat bottom helps, at
>least walking the bike. Turning is more different, almost a new
>experience, very smooth like butter and without moving the
>shoulder
>outward. Perhaps, this is its best riding characteristic, which I
>would recommend people to try.
>
>
>
>
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