[python] Re: Bipolar update

  • From: Olaf Johansson <noll@xxxxxxxxx>
  • To: "python@xxxxxxxxxxxxx" <python@xxxxxxxxxxxxx>
  • Date: Sun, 10 Jul 2011 22:11:46 +0200

Nice! What would happen if you changed the design so that the rear wheel is 
countersteering? That would perhaps make turning radius even shorter? Maybe it 
would make it impossible to ride straight? Making it unrideable. And 


10 jul 2011 kl. 21:26 skrev Vi Vuong <vi_vuong@xxxxxxxxx>:

> Riding hands-free is great, especially when the scenery is nice.  Best 
> comments I got from the trip are:
> That't not fair - from someone riding roller blades
> He's lying on a bike - from a kid
> Can we make that bike? from another kid
> ...
> http://www.youtube.com/watch?v=abNt5v9CsHg
> From: Vi Vuong <vi_vuong@xxxxxxxxx>
> To: Python <python@xxxxxxxxxxxxx>
> Sent: Saturday, July 9, 2011 9:30 PM
> Subject: [python] Bipolar update
> When disassembled, it managed to fit inside a medium luggage (largest that I 
> have), where the micro python would need another inch or so.  Thus it got to 
> go traveling first.  Fortunately, the total weight is under 50lbs, so no 
> extra luggage charge ($100?).
> Climbing is rather poor, as front weight distribution is ~40%.  Walking is 
> tough, and barely with a stick at the front.  Carrying the 25lb folded bike 
> uphill is no fun either, so a upright folding bike is better here, especially 
> in the city...
> Downhill is not too scary anymore with some braking.  I can go faster than 
> going uphill now :)  On the flat, I am comfortable enough to share trail / 
> pathway with pedestrians now (when legal).
> The 2-piece seat is marginal so I had to pick up a mesh back support on the  
> trip, not bad for $1, 
> http://www.google.com/search?q=back+support+mesh&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&hl=en&tab=wi&biw=1440&bih=814.
>   A hotel towel would also helps.  Because the seat rest is coupled to the 
> rear wheel, starting is a little tougher even with sticks, and care is 
> required to ensure that the back seat / rear wheel is straight.
> Luckily, while experimenting with uncontrolled rear wheel, I found that the 
> bike is actually more compliant.  The rear wheel is now mostly free from the 
> seat back, other than some pressure / friction, and straightens out nicely 
> under weight, and seems to move slightly with the front wheel due to the 
> pendulum effect, and probably vice versa (another invisible link like the 
> bango steering http://www.youtube.com/watch?v=jzUr3GI_ulE).  
> There also seems to be some sort of self-stabilizing effect (PSI reduction?) 
> between the two wheels that deserves more analysis, beyond quick all-wheel 
> steering.  Since the camera is mounted to the rear frame, so it's not very 
> obvious that the rear wheel rotates unless you pay attention to the view 
> through the wheel. http://www.youtube.com/watch?v=vswF-qqcwg0   See the PSI 
> test at 1:06-1:15.  The bike feels quite stable as going straight.  I will 
> repeat the test on regular pythons...
> Vi

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