[python] Re: RWS Python (fwd)
- From: Vi Vuong <vi_vuong@xxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Sun, 27 Mar 2011 20:36:58 -0700 (PDT)
Thanks Pascal for the link and translation summary.
Wow, that's complicated. I think I will stick to hands-free and self-centering
design (simple). If the RWS attempt fails, I can always covert it to a trike,
which I had tried with pivot behind the seat, pointing forward, lean steering,
and some leverage on the handlebar, similar to organic engine design. I found
it not very intuitive / natural, fell off server times in corner (wheel flop?),
and prefer the python feel much better.
Vi
________________________________
From: Pascal Buenzli <pascal.buenzli@xxxxxxxxx>
To: python@xxxxxxxxxxxxx
Cc: Vi Vuong <vi_vuong@xxxxxxxxx>
Sent: Sun, March 27, 2011 6:33:21 PM
Subject: [python] RWS Python (fwd)
Hi Vi,
I had seen this one before. The whole blog about this construction can be found
there (in french):
http://velorizontal.bbfr.net/t7559-tad-le-znb
In fact, this is not a real pivot, but a trapezoidal mechanism (two nonparallel
pivoting bars connected to the rear wheel axis on one end and to the frame on
the other end), creating a "virtual pivot point" towards the front. (If the
bars
are parallel (making a rectangle), the virtual privot point is set to infinity
and the rear wheel is just translated (offset to the left or right) without
modifying its angle, whereas if the two bars connect to the frame at the same
single point (making a triangle), this point is the (now real) pivot. Any
configuration in between (making a trapeze) displaces the 'virtual' pivot point
in between...) Somebody else has made some 3D graphics and movies about the
same
(as well as another similar) mechanism: http://oliviercresson.free.fr/s4bc.htm
So actually one might not qualify this as RWS as the effective pivot might
actually be located close to the front wheel. As somebody suggests in the blog,
though, what might matter for that definition is more the main weight
distribution. Debatable and debated...
I also think RWS is in principle a good idea, but it might be tricky to find
good configurations for easy rideability (whatever one means with that - the
french guy from the video comments that he is the only one so far able to ride
his bike. Of course, a matter of training, but also perhaps a 'mother-child'
love and determination relationship? :)
I'd be interested in your results should you try to make one of these!
Regards,
Pascal
---------- Forwarded message ----------
Date: Sun, 27 Mar 2011 13:21:39 -0700 (PDT)
From: Vi Vuong <vi_vuong@xxxxxxxxx>
Reply-To: python@xxxxxxxxxxxxx
To: Python <python@xxxxxxxxxxxxx>
Subject: [python] RWS Python
This one (znb) seems quite controllable, pivot slightly pointed to the rear,
and trail ~zero or negative, and probably gigantic turning circle.
http://www.youtube.com/watch?v=SGlNhdxesbc&feature=related
A RWS python should retain the best features, hands-free, self-centering, low...
RWS seems more difficult because of no direct control of both wheels like the
FWD version by the body / legs. However, if it works, we can gain quite a few
benefits - less PSI / speed, positive trail, bigger front wheel, lots of space
for pivot behind the seat and even handle bar... Should I give it a try?
Vi
[python] Re: dennis renner
* From: Dirk Bonné <dirk.bonne@xxxxxxx>
* To: python@xxxxxxxxxxxxx
* Date: Thu, 23 Sep 2010 07:25:52 +0200
The experiment is as follows: hold rear part vertical and turn the front part
->
on a python we get seat rise. But if we hold the front part vertical, then
turn
the rear part, then the seat will lower on a python. On a RWS the bulk of the
weight is on the front part, so leaning of the front part on turning will be
small (to balance we need to shift weight). So from this assumption there would
be no self centering effect on dennis bike (and the cal poly bike it would
have). Dirk
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