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Old Nov 26, 2012, 09:37 PM
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Canada, ON, Newmarket
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55mm A4 inlet design

I've been hot wire cutting small pusher jets and have built a 50mm edf. I'm now working on a 55mm A4 and need some input on the intake design. Which of the two ideas shown is better? Having the two intake ducts merge ahead of the fan or merge at the face of the fan.
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Old Nov 26, 2012, 09:43 PM
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DanSavage's Avatar
Trabuco Canyon, CA
Joined Nov 2000
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Quote:
Originally Posted by gdimonte View Post
I've been hot wire cutting small pusher jets and have built a 50mm edf. I'm now working on a 55mm A4 and need some input on the intake design. Which of the two ideas shown is better? Having the two intake ducts merge ahead of the fan or merge at the face of the fan.
Both will work equally well, but the top one will not 'whine' as much as the bottom one.
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Old Nov 28, 2012, 08:24 PM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
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i've found that some space between the merge and fan is best unless you do constant area ducts where the fan only get air not the spinner ,with those you need at least a inch between the merge and fan blades...most of the time ...some fan require a bit more.
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Old Nov 30, 2012, 07:25 AM
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Thanks for the input. Here's another question. I'm using GWS fans that have a lip on them. My inlet duct diameter is the same as the fan inner diameter. This leaves me with a small gap where the fan face meets the inlet. What's the best way to deal with this?
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Old Nov 30, 2012, 11:11 AM
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Quote:
Originally Posted by gdimonte View Post
Thanks for the input. Here's another question. I'm using GWS fans that have a lip on them. My inlet duct diameter is the same as the fan inner diameter. This leaves me with a small gap where the fan face meets the inlet. What's the best way to deal with this?
Without an actual measurement to quantify what 'small' means, I'd say leave it alone as it won't affect performance.
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Old Nov 30, 2012, 12:44 PM
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I don't have the fan with me right now but, here's roughly what I'm dealing with.
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Last edited by gdimonte; Dec 01, 2012 at 07:51 AM.
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Old Dec 03, 2012, 11:27 PM
deltas are cool
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Tehachapi ,CA.
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that wont hurt anything ...if any thing it will help stop reversion
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Old Dec 04, 2012, 10:48 AM
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Good to know. That simplifies the build.

Sorry to drag this out but, I have another question regarding your note above on constant area inlets. Would that design provide much improvement over the basic inlet shown above? Is it worth the extra effort?
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Last edited by gdimonte; Dec 04, 2012 at 10:56 AM.
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