[python] Re: Stability Theory
- From: Ray Schümacher <mtb@xxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Tue, 22 Feb 2005 12:30:16 -0800
Hi
At 07:58 PM 2/22/2005 +0100, you wrote:
>From my experience I would consider P3 as stable
>between 5 and 45 km/h. But this is very much depending
>on the rider´s practice.
Remember that this is for "no-hand" type stability - I need to read up on what
is considered easily controllable and how that appears in the equation results,
maybe make those speeds yellow or something. If the bike simply wants to tip
over at low speed and you can easily correct in time, it would still show up
here as unstable. If you go limp and close your eyes at 8Km/h will you tip over?
Most people would feel comfortable correcting for 2-3Hz max, I think.
The equations almost certainly need adjustment for the python position as well;
the hips dampen the pivot and the effective front mass placement is tough
too... I would guess to use your CG as the rear mass and less front mass, with
the front mass a bit further forward. Did you account for the cranks and front
frame/wheel weight? I'll try it out with the pivot K factor too.
>Next I want to do the calculations for my airbike.
>This is significantly more stable above 50 km/h.
Try modelling a standard bike (if you have one!) to get a feel for what these
geometry-vector calculation predict. They seem pretty good for my bike.
>>> - front wheel moment of inertia
>>The value of 50 in/lbs**2 was for a narrow street wheel, so adjust
>>accordingly. It is almost entirely a function of rim and tire weight/mass.
>
>How about a 26"x1.75" MTB front and rear wheel?
probably 2-3x the default for the skinny tires. This will definitely lower the
"stable" speed.
>PS: For calculating the weight of limbs etc:
>Human Anthropometric Data
>http://www.personal.usyd.edu.au/~mslee/ESSwww/lee/zygal/glossary/anthropometry/winter.html
good link
Cheers,
Ray
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