[python] Re: report: pythoon first ride
- From: Dirk Bonné <dirk.bonne@xxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Sun, 11 Oct 2009 22:32:12 +0200
Sorry I messed up the links to the small clip:
http://picasaweb.google.com/lh/photo/MbwmMjrQsh8w8YuyICbt4A
graph1 and graph2 are rigth behind it.
groet,
Dirk
Dirk Bonné wrote:
> Hi
>
> This weekend I had the chance to try the bike out for the first time
> (the bike is still unfinished, but good enough to ride). This first ride
> has been filmed by my wife and can be seen on picasa:
>
> http://picasaweb.google.com/dirk.bonne/Pythoon#5391416625371973074
>
> (notice the name! it got a name!)
>
> Until now I have only been riding a few times up and down our street.
> The behaviour of the bike is somewhat different from what I am used to,
> and so I am a little wobbly. I guess I just need to get used to the bike
> and it will get better.
>
> The good news is that my worries about having my son in the bike were
> ungrounded. Even during the first kms he was playing by hanging out of
> his "box" and holding a wooden stick grinding it against the tarmac. I
> simply do not notice him shifting weight very much.
>
> The bad news is that the bike steers like a truck. Before I started the
> project I actually made a graph comparing the pythoon, the baby python
> and the p3 and I didn't see anything unusual. I recalculated and put it
> on picasa:
>
> http://picasaweb.google.com/dirk.bonne/Pythoon#5391423541426608210
>
> It shows the change in seat height when turning the front part. The
> pythoon has a stronger self centering then baby python, but still less
> then the P3 of Jürgen. But in practice the self centering feels very
> strong, stronger then I remember from trying a 26" python (birdcage of
> Serge). Either my program to calculate the curves is wrong (quite
> possible), or it has to do difference with weight distribution caused by
> the long wheelbase. On this bike there is more weight on the front wheel
> then on any other python. In any case this shows that the graphs are not
> useful at all. What is needed is a graph depicting the needed torque to
> sustain a turn.
>
> I am considering my options. I don't like the idea of putting a wide
> steer on the bike to help with turning (the current steer is very
> narrow). I think I am going to increase the pivot angle. It is now
> already on 70degrees - I could try 80degrees. This is a lot of work
> because I have to re-braze on both the rear and the front. But on the
> other hand it would be interesting to see what such a high pivot angle
> has as an effect. I calculated the graphs:
>
> http://picasaweb.google.com/dirk.bonne/Pythoon#5391428883434182962
>
> The graphs show that the self centering (in seat height change) should
> be smaller even then then baby python. In term of torque, I do not know.
>
> Dirk
>
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