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Old 01-18-2014, 04:38 PM   #1 (permalink)
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Orion Speedtrike Testing:You-Tube

Ran across this:

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Old 01-18-2014, 11:31 PM   #2 (permalink)
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Looks like Attached flow, on a shape "Much" steeper than "the Template". How can it be?
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Old 01-20-2014, 05:24 PM   #3 (permalink)
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how can?

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Originally Posted by CFECO View Post
Looks like Attached flow, on a shape "Much" steeper than "the Template". How can it be?
I do not have an answer which is as good as your question.Some thoughts:
*In Hucho's 2nd-Edition he shows a single image of a body of revolution which is optimized for low drag.It's like a 'laminar' profile which has it's maximum cross-section well aft on the body.It has a 'fast' rear contour.There's no further mention of it.
*It may behave as the NACA/Morelli shape,which has really low drag with high ground clearance,and then it's Cd falls apart when lowered into 'normal' ground clearance.(Cd 0.17 became Cd 0.35 in Morelli's case)
*Orion's high ground clearance may allow for the 'jet pumping action' which truncated boat-tailed bodies experience in free flight,a condition where the flow is more axially symmetrical,and the under flow it highly energetic,with equal pressure/velocity.
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*Hucho says (for road vehicles) that beyond 23-degrees,we'll have separation and a transition to a squareback wake as you can see in the #14 drag table of the aft-body rear inclination thread.Between 28,to 32-degrees,the wake would dance back and forth between fastback type and squareback wake,with pulsations,booming,and maximum drag.
*W.A.Mair shows full separation beyond 22-degrees.Pretty close agreement.
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*It could be that Orion's shape only works for Orion-like vehicles.I'm hoping that Neil Blanchard will have something from Goro Tamai's book which will help.I've ordered the book,but it is sold out on Amazon and I'll just have to wait it out for delivery.
*I compared Kach22i's VW Volkhart Sagitta aft-body wind tunnel smoke flow photo with a protractor and am seeing separation beyond 22-degrees.
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Old 01-20-2014, 05:32 PM   #4 (permalink)
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It really looks like it "Should Be" better, in the other direction, or maybe I'm just stuck on that because of my "backwards" VW project!
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Old 01-20-2014, 06:12 PM   #5 (permalink)
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better

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Originally Posted by CFECO View Post
It really looks like it "Should Be" better, in the other direction, or maybe I'm just stuck on that because of my "backwards" VW project!
Maybe one day we'll get a Cd for Orion.I suspect that everyone would like to see numbers for it.
As far as I know,Eiffel and Fachsenfeld are the only two investigators to publish Cds for 'reversed' bodies.
Eiffel's reversed 'ice cream cone' doubled in drag when backwards.
Fachsenfeld showed a sreamline body of 6:1 fineness ratio which with wheels,and in ground effect,would come in at around Cd 0.13.Which isn't bad,but the 'normal' body has about 14% lower drag.That wouldn't be a problem for a lot of folks.
Perhaps Tamai's book can expand the database for these exotic shapes.
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Old 01-22-2014, 12:49 PM   #6 (permalink)
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Here is a link to the construction of this trike.
The Recumbent Bicycle and Human Powered Vehicle Information Center

It held the trike speed record for a couple years at around 67mph. Can't find the exact number right now.

JJ
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Old 01-23-2014, 10:00 AM   #7 (permalink)
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Quote:
Originally Posted by CFECO View Post
Looks like Attached flow, on a shape "Much" steeper than "the Template". How can it be?
I think it is not as steep as it looks on the YouTube video. If you look at the second page of his build blog there is a nice side view of the mold.

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