[python] Re: Self Centering vs. Wheel Flop

Stephan Schöling wrote:
> Hej Dirk,
>
> i'm not the best in theoretical physics, even not a good
> mathematician, so let me thank you for your lessons.
> Be honest if you think my skills are to low to understand these things
> or i am just boring you with that !
Hey now Stephan, you are getting a wrong impression here.I did get the
theoritical mechanics during my education but that is really very very
long ago.

>
> dirk.bonne@xxxxxxx wrote:
>> Hi Stephan,
>>
>>
>> Stephan Schöling wrote:
>>  
>>> Hej Dirk,
>>>
>>> please, can you explain why you see a system with two weightpoints ?
>>> I only see the Center of Gravity (CoG) and can´t understand why the BB
>>> should be important.
>>>     
>> Well it is only to model the weight of the bicycle and the weight of the
>> rider. Some of it is on the front part and some of it is on the rear
>> part.
> Ok, i got that. We can measure the wight of the bike and the
> proportion front/rear easily.
> But how can we do this with a rider ?  We would need 2 persons to read
> the scales under the wheels at _exactly_ the same time, which is
> nearly impossible.
> So we have no usable data of the weight proportions of the bike with
> the rider, or has anyone ?
It is some work but doable: (not 100% precise). Here is a possibility:

1) take your bike in your hands, stand on the scale: totalw
2) Put bike on grond again, put the front wheel on the scale, rear wheel
somethign whit the same height as the scale. Get on the bike and read
the scale: frontw

the

    rearw = totalw - frontw

and Cog is:

    CoG = WB * frontw / totalw

with CoG measured from the rear wheel.

3) Now the weight of the feet on the pedals. If you are willing to take
a error into acount: sit on ground, put the scale in front of you,
strech your legs and put your feet on the scale. That will be about  the
weight of your legs on the pedals (I get about 10kgs).

    legsbbw=10kg.

The weight of the front part: part the python in two parts and weigh the
front part. The CoG of the front part along can be found visually - not
so difficult.

Now in the newton model I would:

    put the weight of the front part in the CoG of the front part
    put the legsbbw at the BB
    put the totalw - legsbbw - frontpartw at the CoG of the bike.


groetjes,
Dirk

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