[python] PX.5 report

Today I finished PX.5:

  Pivot angle: 63 deg
  Trail: -47 cm
  Seat height: 33 cm
  Wheelbase: 118.5 cm
  Clearance: 11 cm

You might wonder why I fell back to 63 deg?
I would call that experience an eye opener.

As I told you, I adjusted the  bike for my legs by welding another
BB about 10 cm in front of the original one, so the front part became
longer and heavier. Then I mounted gear shifter and rear brake.

The first test ride was surprising because the wheel flop had
reappeared and the bike was not rideable (pivot 55 deg).

As I had to improve the clearance anyway, I cut the 35x35 mm
backbone, bent it and welded it: pivot angle 57 deg.

Test ride : wheel flop!
Cutting and welding: pivot angle 59 deg.
Test ride : wheel flop!
Cutting and welding: pivot angle 61 deg.
Test ride : wheel flop!
Cutting and welding: pivot angle 63 deg.
Test ride : wheel flop was gone, bike rideable and stable!

Absolutely amazing how the behaviour changed from
unrideable to stable within a range of 2 degrees.

This reminded me of a balance where a minimum change of
weight decides on equilibrium or mismatch.

Now, here a formula would be very helpful.

Here the stability program of Ray cannot help because it does not
consider the dynamic perturbation of pedalling legs.

Anyway - tomorrow I will make PX.5 ready for the road and
start the high speed testing this weekend as the snow is melting
away rapidly (finally!).

Picture of PX.5 on the mod page:
http://www.python.tieflieger.net/pics/Python%20PX.5.jpg

Cheers,
Jürgen. 

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

This is the Python Mailinglist at freelists.org

Listmaster: Juergen Mages jmages@xxxxxx

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

Other related posts: