[python] Re: Stability Theory
- From: Ray Schümacher <mtb@xxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Fri, 18 Feb 2005 07:54:12 -0800
At 03:59 PM 2/18/2005 +0100, you wrote:
>Hi mad recumbent scientists ;-)
>(I assume that this mailinglist is the most weird recumbent
>hombuilder forum in the internet - but I love it)
Somebody has to do it...
>Playing around with Ray´s app I got confirmed at least one
>thing, that is noticeable in real life too:
>
>The more weight is on the front wheel or pivot, the more
>stable the python is when coasting.
Traylor's bikes have almost all the weight up front, as did penny-farthings. I
noticed that moving the front mass location forward always helped, until it
moved a bit forward of the contact patch.
>>>Then we could just prolong the wheelbase!
>
>I have another proposal:
>Why not move the pivot about 20 cm towards the rear - that
>means behind the seat.
In the calculator, I tried:
wheelbase 52
trail -10
pivot 16deg
rear mass ht 16
rear mass dist 22
front mass ht 15
front mass to pivot 13
It appears very stable! But it also seems very sensitive to variations.
An angle of 42 and trail of -12 also appears usable. It is less sensitive to
wheelbase differences.
>High time to build an experimental scrap python - I will call
>it PX.
>Experiments sceduled so far:
>
>- pivot angle of 60 deg and smallish negative trail
>- pivot moved 20 cm backward
>- rubber pivot
>- four bar linkage pivot
- telescopic rear frame, for wheelbase adjustment
- clamp or screw adjustable pivot angle (screws like on telescope mount alt
adjusters). Two would be needed, one each side of the pivot.
Changing the distance from the front axle to the pivot might be too hard.
>Link not worky.
Eek! They just re-did their site. The new page:
http://ruina.tam.cornell.edu/research/
is much improved though. The thesis is at:
http://ruina.tam.cornell.edu/research/topics/bicycle_mechanics/papers/comparisons_stability_analysis.pdf
Also, I just found:
http://www.johnforester.com/Articles/BicycleEng/dahon.htm - look about halfway
down for
General Stability Considerations
form http://www.johnforester.com/Articles/bikebooks.htm
Ray
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