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| This thread is privately moderated by turbored21, who may elect to delete unwanted replies. |
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Jun 24, 2009, 06:40 PM
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#1 |
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Registered User
Join Date: Oct 2006
Location: Moundsville WV
Posts: 2,265
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Equation for figuring the thrust tube on an edf?... FSA?!
Help Don!
Calling on the expert! .. just as the title reads.. im building a kamdax mig15 into an Electric im using a hobby people F16 fan and housing.. i want to make a proper exit tube for it need to know what to measure and how to do the math to get the most out of this little bugger! thanks in advance |
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Jun 25, 2009, 06:51 PM
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#2 |
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Wonderfully Wicked
 
Join Date: Jan 2002
Location: Willoughby, Ohio
Posts: 7,925
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I always us 80% of the fan sweep area (FSA). The fan sweep area is the doughnut shaped ring that the fan blades push air through. You need to measure the diameters on the fan you are using. The calculate the exit diameter is easy the simplest way to do is like this:
De= sqrt(.80) * sqrt(D*D - d*d) De= diameter for 80% FSA D= rotor diameter d= diameter of rotor spinner/motor (depends on fan used) .80 = 80% FSA I will post a photo and do an example. Don |
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Jun 25, 2009, 11:50 PM
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#3 |
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Registered User
Join Date: Oct 2006
Location: Moundsville WV
Posts: 2,265
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hey don thanks alot!... that will be awesome i wanna get this figured out so i can get the most out of this little guy
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Jun 26, 2009, 12:03 AM
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#4 |
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Wonderfully Wicked
Join Date: Jan 2002
Location: Willoughby, Ohio
Posts: 7,925
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Are you using the stock HP 3 blade fan/rotor?
Don |
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Jun 27, 2009, 01:54 AM
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#5 |
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Registered User
Join Date: Oct 2006
Location: Moundsville WV
Posts: 2,265
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yes don i will be
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Jun 27, 2009, 08:59 PM
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#6 |
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Wonderfully Wicked
Join Date: Jan 2002
Location: Willoughby, Ohio
Posts: 7,925
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OK here we go.
De= sqrt(.80) * sqrt(D*D - d*d) De= diameter for 80% FSA D= rotor diameter d= diameter of rotor spinner/motor (depends on fan used) .80 = 80% FSA Measuring the fan we get: D= 56 mm d= 24 mm De= sqrt(.80) * sqrt(56*56 - 24*24) De= .8944 * sqrt(3136-576) De= .8944 * sqrt(2560) De= .8944 * 50.596 De= 45.25mm = 1.78 " |
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Jun 27, 2009, 09:13 PM
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#7 |
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Registered User
Join Date: Oct 2006
Location: Moundsville WV
Posts: 2,265
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awesome don.. thanks!
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Jul 14, 2009, 05:07 PM
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#8 |
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Registered User
Join Date: Sep 2003
Location: Houston Intercont, Texas, United States
Posts: 520
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Here's a related question, does the exit have to be round? I know its probably the easiest to form, but could the duct exit be oval or some other shape without sacrificing too much performance?
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Jul 14, 2009, 05:12 PM
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#9 |
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Wonderfully Wicked
Join Date: Jan 2002
Location: Willoughby, Ohio
Posts: 7,925
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I have used slightly oval at times but round I believe is the best as it distributes the airflow evenly. The EDF F117 I had had long rectangular slots and it worked great but they also had a nice gradual transition from round to rectangle to reduce losses as much as possible.
Don |
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