[python] Re: BB in lower Position

  • From: Dirk Bonné <dirk.bonne@xxxxxxx>
  • To: python@xxxxxxxxxxxxx
  • Date: Wed, 16 Aug 2006 09:15:57 +0200

Jürgen Mages wrote:
> Thorsten Borm wrote:
>> Until today my experience with the 20"-Python was 330 km. I always
>> missed the really safety and relaxed feeling because I needed 1 meter of
>> the road for myself. I was always afraid of other traffic members at
>> narrow roads and speed above 20 km/h. My biggest trip was 38 km at one
>> day - but I was totally broken at the end.
>> Today I made a little test with the geometry of my 20"-Python. I changed
>> the BB from above of the frame tube to a position below of the tube
>> (-10cm) which you can see at the picture. I don't know why, but there is
>> a big progress:
>> Only little nervous Zig-zags, much more self centring effect, more
>> safety feeling at higher speed and a better view towards the road. Now
>> I'm able to drive nearly the line I want to. The position is still high
>> enough to keep pedalling at narrow turns. With best regards
>> Thorsten
>
> Interesting info. Good that you did not gave up!
>
> I guess that what happened to you was quite similar to my experience
> with the PX.5 one year ago. I made the BB-EOS 8 cm longer to adjust
> it to my length and suddenly the bike was no longer rideable for
> me (before it was ok).
>
> The gravity center of the front part became too dominant/high and
> the wheel flop effect started to overpower the self centering.
> Resulting that I felt like sitting on a seesaw with the front part
> moving from one side to the other. After I made the steering angle
> 10 degrees steeper the bike was normal again.
are you saying that on your own python the self centering is the most
dominant force, more then the weight on the pedals?

I just did a little test: I sat on the bike, hands on the floor keeping
the bike straight up, and feet resting on the pedals. Then I tried
turning the front part and see for which the turning angles I have to
use force to stay at that turning angle (i.e. where the self centering
is dominant).

For quite a big range (I guess -15 -> +15degrees), self centering is so,
that it does NOT come back to straight by its own. Rather it is
"neutral": it does not tend to go further in a bend but does not tend to
go straight. Only further outward I need to use force to keep a that angle.

It is difficult to test this realistically this way, its difficult to
shut out for sure the  tonus in the legs. How heavy would a typical pair
of legs be on the pedals? may be I could integrate it in my program if i
had that data.

the sun is starting to peep from behind the clouds again! hurray!
dirk
============================================================

This is the Python Mailinglist

//www.freelists.org/list/python

Listmaster: Jürgen Mages jmages@xxxxxx

To unsubscribe send an empty mail to 
python-request@xxxxxxxxxxxxx
with 'unsubscribe' in the subject field.

============================================================

Other related posts: