[python] Re: fully faired 2-wheel Python
- From: stephan@xxxxxxxxxxxxx
- To: <python@xxxxxxxxxxxxx>
- Date: Sat, 27 Jan 2007 17:33:29 +0100
Hi Dirk,
(and all others interested in aerodynamics)
First to say, i am thinking about things which are far away from the dutys of
the next days.
My "42"-Bike wants to have some more parts fixed, its not painted yet, I
havn´t learned to ride it yet and i shouldn´t forget that i have much more
important things to do in "real life" (tm).
BUT, i cant help, its so much interesting to think about these python things.
I live in a flat and sometimes windy landscape, last week we had the Storm
named "Kyrill", so I can`t stand ...
hopeless ...
>Am Freitag 26 Januar 2007 18:17 schrieb stephan@xxxxxxxxxxxxx:
>> ... I wonder if a nose-fairing fixed to the front part really comes off badly
>> whith side wind. I think a aerodynamicly shaped fairing should make the
>> bike less suspectible for side wind. Am i wrong ?
>>
>
>either way, i think a python bike will recieve some "wind induced steering"
>with fairing. However, if the wind shield is relatively small, the side wind
>effect should be minor.
Brainstorming:
Now, we have side wind effects on any vehicle.
Bikes (like all slower vehicles) are more responsible because the result of the
addition of the front wind component (by driving forward) and the side wind
component is more affected by the side wind (forward component is low).
EG: Driving a bike with 30 kmh (0°) with 30 kmh side wind (90°) causes
seeming wind from 45°. Driving e.g. a Motorcycle with 100 kmh and same side
wind the seeming wind comes from ~27°.
This is the reason i think good aerodynamics for a bike _should include the
side wind_, only for fast vehicles you can ignore it.
Next point is the bad (high) Cw-value of a bike. I think the wheels are worst,
then the frame and the driver. Disc-covered wheels won´t be very helpful,
everyone who tried them in windy conditions knows that. That bad behavior of
disc covers is caused by their flatness, wich makes them "sailing". There are
big forces made by these "sailing" effects !
Also a single windshield isn´t very helpful too, most are shaped for front
winds only.
So, why not raise the level up to a fairing that HELPS the driver even with
front and side wind aerodynamics. (... and rainy weather! ). It should be
possible to develop a Bikefairing that has no (or less) disadvantages (side
wind, wheigt, sight, costs, more ?)
And now we are at the point the Python steering geometry may HELP.
The fairing has to have its biggest part near the steering BB / the drivers
hip. Stronger sidewind will help to steer against it (Wind from the right
pushes to the left, pyhon steers right).
Too big surfaces at the front and rear edge will cause bad steering effects to
a Center steered Bike.
If we have small and round (globular?) surfaces at the front and rear edge the
sailing effect should be ignorable low here. And the wind should be able to
pass over and under the fairing, that makes it more stable.
I think a good fairing for the python has to be a bit different to all known
because its a unusual bike ;-)
Fairings like Alleweder or Leitra are good for 3-wheelers, nothing for python
2-wheelers.
So you can forget my little drawing i made yesterday. A new design has to be
developed.
I have some ideas in my mind, but should sort them first.
> I'm thinking of shields like this:
>
>http://www.humboldt1.com/~mhp/gto.htm (greenspeed trike)
Very nice for a trike ! Good looking, professionaly made.
Not easy to Copy-It-Yourself (C.I.Y) ;-)
>Only if the wind ends up coming from halfway behind (i.e. 4 o'clock), it
>should accelerate and steer in some respect.
See above, why i think it would steer a 2-wheeled python. Maybe it accelerate
in 90° wind, because that seems to be the best wind for sailing with a shield
shaped like that :-)
A question to Jürgen (still reading this ?): Does the wheelcover on your P3
affect the steering in windy weather ?
Stephan
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