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Old 06-03-2011, 06:19 PM   #21 (permalink)
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beer,you'll want to keep an eye out for flutter.The steps will have a natural frequency and harmonics of that frequency in which they'll vibrate like a tuning fork.If not sufficiently stiff enough for dampening they can shake themselves apart in the vortex.
Yep, I'm aware of that, kind of the same affect which happened with "galloping gertie".
What I also want to keep in considoration, is that weak/thin pieces will vibrate quicker, and couse vortexes of there own.


So I've to make a HUGELY heavy bulky louvre to make it strong enough,
the weight will compensate for the lift generated. (just joking)

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Old 06-03-2011, 06:22 PM   #22 (permalink)
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It sounded familiar...
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Add flying buttresses & then add the louvers. 70's-80's fastback flashback! ...had a Z with those things.
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Old 06-03-2011, 06:25 PM   #23 (permalink)
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It sounded familiar...
Looks cool to, do you have a link or a name so I can get more info?
But I'm not sure if it for drag reduction the angle is still quite agressive.

Last edited by beer; 06-03-2011 at 06:43 PM..
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Old 06-03-2011, 06:49 PM   #24 (permalink)
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aerohead -



So at air speed X it could shake apart. Does that also mean that at air speed Y it could perform at it's best? Is there an optimum step shape for every MPH?

CarloSW2
At some speed the span would reach its natural frequency and begin to resonate with some displacement amplitude.The vibration could work-harden( if you will ) the material causing it to fracture like a coat hanger bent back and forth for a few cycles,or just explode as I have witnessed with some of my prototypes.
At a higher velocities,the span would reach harmonics of its natural frequency and vibrate at these,as in a piano,going up through all the octaves.
Harley Davidson has critical engine rpms which must be avoided or the bottom end will self-destruct.
Changing the velocity will alter the pitch,and move the frequency out of danger perhaps,although if vibration occurs at 'normal' driving speed,we've got to stiffen the part,or maybe shred the major vortex and blast it into smaller,homogeneous eddies of higher frequency using VGs as we see on mirrors for acoustic tuning.
------------------------------------------------------------------------
Aerodynamically,the backward facing steps,if following close to the 'Template' profile,will perform the same at any speed above 20 mph.There shouldn't really be a 'sweet-spot'.
If the curvature is hyper-'template',that's okay 'cause there'll be no major stall in the out flow region.Laminar flow,no turbulence.
If the step curvature is hypo-'Template',the the whole device will be embedded within strong turbulence and must be strong enough to survive the constant buffeting.And it WILL get worse with higher speed as a square of the velocity.
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Old 06-03-2011, 06:51 PM   #25 (permalink)
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It sounded familiar...
This would sell! I think Frank Lee would agree.Frank?
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Old 06-03-2011, 07:57 PM   #26 (permalink)
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As long as it says "I have balls like basketballs" then yes, it will sell.
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Old 06-04-2011, 01:27 PM   #27 (permalink)
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like basketballs

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As long as it says "I have balls like basketballs" then yes, it will sell.
Maybe at some point there'll be some official right of passage into manhood and man wannabes will know if they're 'there'yet, instead of turning to Smoky and the Bandit,The Fall Guy,Dukes of Hazard,The Fast and the Furious,and Terminator for clues.
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Old 06-04-2011, 01:40 PM   #28 (permalink)
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One can only hope. I don't see any sign of that.

I recently spoke with a lad who is a participant in this mud truck pipe rapping B.S. He said the purpose of it was to establish a pecking order.

He also said he could be heard from 3 miles away, but he only does it at school and out in the country.

OH, well then, carry on!

This same kid said, unprompted, that gas will be gone in 20 years.

How does one reconcile in one's mind (no matter how small it may be) the idea that gas will be gone in 20 years so let's put 100 miles/day on a 10 mpg P.O.S. while accomplishing nothing whatsoever?

I saw this same kid's truck idling unattended in a parking lot this spring. I parked, went in, wandered throughout the store and did my shopping, came back out, and that truck was still there idling.
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Old 06-04-2011, 02:16 PM   #29 (permalink)
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hope

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One can only hope. I don't see any sign of that.

I recently spoke with a lad who is a participant in this mud truck pipe rapping B.S. He said the purpose of it was to establish a pecking order.

He also said he could be heard from 3 miles away, but he only does it at school and out in the country.

OH, well then, carry on!

This same kid said, unprompted, that gas will be gone in 20 years.

How does one reconcile in one's mind (no matter how small it may be) the idea that gas will be gone in 20 years so let's put 100 miles/day on a 10 mpg P.O.S. while accomplishing nothing whatsoever?

I saw this same kid's truck idling unattended in a parking lot this spring. I parked, went in, wandered throughout the store and did my shopping, came back out, and that truck was still there idling.
We probably ought to start something in the Lounge where everyone can share their horror stories.
I've certainly got mine.I could say some very mean and ugly things.
I could also mention the times when folks of all stripes have come up and said,"say,is that aerodynamics for better fuel economy?"
A few of those will keep you in the game.
Funny world!
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Old 06-05-2011, 06:24 AM   #30 (permalink)
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We probably ought to start something in the Lounge where everyone can share their horror stories.
I've certainly got mine.I could say some very mean and ugly things.
I could also mention the times when folks of all stripes have come up and said,"say,is that aerodynamics for better fuel economy?"
A few of those will keep you in the game.
Funny world!
+1 for hope

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