[python] Re: Nice Python video
- From: Vi Vuong <vi_vuong@xxxxxxxxx>
- To: "python@xxxxxxxxxxxxx" <python@xxxxxxxxxxxxx>
- Date: Sun, 3 Mar 2013 21:18:30 -0800 (PST)
Hi Jürgen,
Folding was the design goal for the Bipolar. Pushing / pulling the bike around
is its most pleasant aspect. Flying in a suitcase, taking bus/train, and
riding in small boot/trunk are all basic requirements.
Orignally the rear pivot was locked to the seat back. Loosening the rear pivot
for auxiliary steering was experimental. Luckily there was no shimmy up to
14mph. The headtube pivot can be tightened down to damp out disturbance.
Resting hand on the handle bar also helps. Once the wheel gets rolling,
stability improves but who knows, there may be another resonance beyond 14mph
waiting to be discovered. Make sure you have proper crash protection...
Regarding recommendation, it's a yes for an experienced rider who is willing to
accept the compromise of a folder (compactness, complication, lightness...).
The
rear pivot is just a folding mechanism (readily available), and other folding
methods will do. Rear steering turns out to have little/rare use, and the
disturbance are manageable. Thus the focus is back on folding (removable seat
(done), folding hammock seat? magnet wheel coupling? custom case?)
On related news, the Tripolar carries on the steering experiment quite nicely.
It gets low-speed shimmy with half of the load on rear wheels compared to the
Bipolar. However, the onset can be prevented and even violent shaking can be
dampened quickly via handlebar, http://youtu.be/VVPdAVLJZC0
Here are modifications after initial build:
Cut down seat headrest to fit inside MINI's boot; removed dampening spring
(passive) to allow quick folding; added handlebars for active control of rear
wheels. The rear wheels have "invisible" linkage. The coupling gets stronger
with speed (difficult pulling the wheels apart). Lean steer is easier with
handlebar, but still take some getting used to. While leaning with upper body,
it's difficult to turn with legs, so the rear wheels do most of the turning.
Ironically, the front pivot functions mostly as a folding mechanism :)
Cheers,
Vi
>________________________________
> From: Jürgen <jmages@xxxxxx>
>To: python@xxxxxxxxxxxxx
>Sent: Friday, March 1, 2013 1:23 AM
>Subject: [python] Re: Nice Python video
>
>
>Thanks Vi,
>
>professional made video! I will add it to the list in our wiki
asap.
>
>I have seen your video of a high speed test with the bipolar. It
seems that the rear part does not shimmy - right? Would you
consider it a stable and recommendable design?
>
>Best Regards,
>Jürgen.
>
>Am 21.02.2013 09:53, schrieb Vi Vuong:
>
>http://www.therecord.com/videozone/887896--a-reason-for-being
>>
>>I have been conresponding with Terry and have invited him to
share his experience with the list.
>>
>>Vi
>>
>>
>>
>
>
>
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