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Old 08-28-2011, 06:18 PM   #31 (permalink)
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Quote:
Originally Posted by redyaris View Post
When you find a straight sided fairing that that does not "generate" side force please let me know. That way I could make that the front of the motorcycle and have no aerodynamic drag force at all.

It is the curve that generates the lift ,that being a differential pressure on either side The bike you have built would generate far less side lift than my original drawing .My idea would have a lower overall drag but the forces from side winds would be far higher.The entry areas you use and which will have to use I think reduce the lift from the curved sides .

I'd love to know why Allert works so well!

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Old 08-28-2011, 08:55 PM   #32 (permalink)
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Flat surfaces generate lift just as well as curved surfaces. You need to find some experemental evidence that quantifies the forces and the derection in which they act. Without numbers I am afraid you do not understand the matter/problem before you.

What you need to know is HOW Allerts' bike works so well.

My next iteration of the rear cargo "box" will have curved surfaces...

Last edited by redyaris; 08-28-2011 at 09:11 PM..
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Old 08-28-2011, 10:55 PM   #33 (permalink)
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Quote:
Originally Posted by redyaris View Post
Flat surfaces generate lift just as well as curved surfaces. You need to find some experemental evidence that quantifies the forces and the derection in which they act. Without numbers I am afraid you do not understand the matter/problem before you.

What you need to know is HOW Allerts' bike works so well.

My next iteration of the rear cargo "box" will have curved surfaces...
Can you offer any link to that ? I'd love to talk to Allert's builder but that doesn't seem possible.

As for understanding ..you are completely right ,which is why I'm asking for comments and assistance here .

Last edited by PeterS; 08-28-2011 at 11:43 PM..
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Old 08-28-2011, 11:09 PM   #34 (permalink)
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Old 08-28-2011, 11:50 PM   #35 (permalink)
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Allert LOOKS as if it should be subject to considerable buffeting from side winds but he reports that it is not .From my reading so far this seems difficult to understand ,especially with reference to the last diagram I posted .

Do you have any ideas as to why this is so ?
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Old 08-29-2011, 01:12 AM   #36 (permalink)
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Personally I'd take Allert's experience over a diagram.

And Allert IS the builder.
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Old 08-29-2011, 02:12 AM   #37 (permalink)
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''Dutch efficiency enthusiast Allert Jacobs'', thanks Frank ,I hadn't realised that .

I agree that Allert's bike is proof of concept but I just don't understand how !!
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Old 08-29-2011, 07:30 AM   #38 (permalink)
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Quote:
Originally Posted by Frank Lee View Post
Personally I'd take Allert's experience over a diagram.

And Allert IS the builder.
As well as the designer, test pilot, blogger, etc !

I believe he explained the added side force in the rear counter acts the front effect.
Remember, 2 wheelers use counter steering and leaning to turn. The side radius of the tire is why they turn at speed. The wind pushing the rear of the bike over actuall steers it back into the wind. This can be felt in crosswinds with a rear passenger.
Allert states the problem with front only fairings is there is no side wind ballance. When he had only the front fairing, the bike behaved so badly he almost stopped the project.

He also reccommends putting on the rear one first, then adding the front for safety reasns.
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Old 08-29-2011, 06:03 PM   #39 (permalink)
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OK ,by those criteria this should work quite well .



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Old 08-29-2011, 07:12 PM   #40 (permalink)
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build a model and roll it down a ramp and measure stuff. Add a couple little diy electric eye timers to make it more like a science.

Note, it needs to be going pretty fast for accurate scaling, moreso the smaller the model, so maybe a launcher and a net at the ends of a bit of track. (air launcher? spud gun?) and note several times and distances (should be decelerating) and figure out the cda curve. Then weigh it and figure out A (and crr with similiar but slower tests)

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Last edited by dcb; 08-29-2011 at 07:19 PM..
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