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Old 04-25-2007, 12:09 AM   #1
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Shop Vac and a Thread

Playing around with fans and blowers and yarn and such, I found that a long piece of thread inside the blowing end (reverse) of a shop vac gives somewhat of an idea on aerodynamic shapes around the car.

The thread can't be too long.... 3-4 feet or so... and there is some turbulance from the vac... but pointing the contraption at things like the mirror or the cowl gives an idea of what is going on there.

BTW, I did this a week or so ago and was not too sure of the hood result.... it seemed the airflow was center out quite a bit. But today I saw the same thing on the freeway with yarn taped to the hood.

Simple... not too precise... but when you see that thread sucked right into the cowl or that nice taper around the mirror followed by the nasty turbulance right behind it.... I think it provides some cheap and easy insight.
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Old 04-25-2007, 02:33 AM   #2
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Brilliant idea!!! smoke trail without smoke!! great way to test an Airtab!!!
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Old 04-25-2007, 06:04 AM   #3
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If, for some crazy reason, you want to try to smooth out the airstream some, you can bundle together soda straws and blow the air through them. That should give you a less turbulent stream of air. But, it may cut down on the flow too much.

I have a leaf blower here that I have thought about using to do the same thing you did with the shopvac. I am glad to hear that it seems to work.

Did you use a thin piece of thread or a piece of yarn?
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Old 04-25-2007, 07:16 AM   #4
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Yeah I read about the tube approach.... might consider it, but after I think hard about buying a super high power vac :-) Or I might check out my leaf blower too.... thanks for the reminder.

Thread at first, by accident, because the craft store was closed and KMart did not carry yarn. Then I tried the yarn, but it turned out too heavy and I went back to the thread
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Old 04-25-2007, 07:36 AM   #5
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Hey leaf blower great idea I have one of those too and it is variable so you can test at different wind speeds. We used to have a big squirrel cage blower that put out 60 mph wind in a 2 square foot duct that would work pretty good too - could do the entire front end at a lower speed maybe 20mph by the time it was spread out.
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Old 04-25-2007, 07:48 AM   #6
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Quote:
Originally Posted by lca13 View Post
Then I tried the yarn, but it turned out too heavy and I went back to the thread
Cool, I was wondering about yarn being too heavy...
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Old 04-25-2007, 08:01 AM   #7
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Interesting thread...
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Currently getting +/- 50 mpg in fall weather. EPA is 31/39 so not too shabby. WAI, fuel cutoff switch, full belly pan, smooth wheel covers.

Now driving '97 Civic HX; tires ~ 50 psi. '89 Volvo 240 = semi-retired.
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Old 12-21-2007, 04:28 PM   #8
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I have a leaf blower that I was just about to power a skateboard with. I'm going to do this, and post pics...
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Old 12-21-2007, 04:36 PM   #9
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LOL, like jet powered? Dont forget the afterburner
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Old 12-23-2007, 12:15 PM   #10
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HAH! no!.. like geared to a wheel... Although the guy with the skateboarding speed record at bonneville (????) used a pulse-jet...

I'm building a powered skateboard to end them all... every powered skateboard up to this point has been bogus. I'm thinking less "powered skateboard," more "stand-up motorcycle." Fully suspended, with mechanically articulated steering. Another topic entirely, just... explaining.
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