[python] Re: Bipolar update

  • From: Olaf Johansson <noll@xxxxxxxxx>
  • To: "python@xxxxxxxxxxxxx" <python@xxxxxxxxxxxxx>
  • Date: Mon, 11 Jul 2011 09:56:22 +0200

I'm probably just envious on your easy-to-fold frame design. 

Does the bike slither more when you go uphill and have to push hard on pedals ( 
increasing the body's side-to-side movement?)

As for the snake skin, don't forget the fangs!


Olaf




11 jul 2011 kl. 09:17 skrev Vi Vuong <vi_vuong@xxxxxxxxx>:

> if the rear pivot points forward, the rear wheel probably would counter steer 
> and makes the bike unride-able at 60 deg.  As is, I can park the bike with 
> the wheels turned in opposite direction to make it look uninviting :)
> 
> Looking at the second video from an observer point of view, the bike does 
> meander more like the real animal.  http://www.youtube.com/watch?v=abNt5v9CsHg
> Maybe it's time for a python skin shell (costume)... 
> 
> 
> From: Olaf Johansson <noll@xxxxxxxxx>
> To: "python@xxxxxxxxxxxxx" <python@xxxxxxxxxxxxx>
> Sent: Sunday, July 10, 2011 1:11 PM
> Subject: [python] Re: Bipolar update
> 
> 
> 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 
> theft-proof.
> 
>  
> Olaf
> 
> 
> 
> 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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