Making a Shroud

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jhdeval

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I have a stupid question should the fan fit into the shroud or just as close to the fan hole as possible?
 
Common to put 1/2 of fan thickness in shroud, 1/2 out. Dont know why, but that is what is written. and usually have about 1/2 inch clearance so a 18" would take a 19" hole: remember the motor rocks a little...
 
The reason that half the fan is exposed out of the shroud or in some cases the shroud has the fan outer edge exposed on the bottom half, is that the fan is not only axial flow but centrifugal / radial and allowing the air to spill off the rear half of the fan radially allows it to expel considerably more volume of air from the shroud plenum.
 
The highest volume and most efficient CFM is produced 1/2 the blade depth into the shroud.
Believe it or not, they work best if the fan has a tube to work in. (Not critical, just most efficient)

Like this.
 

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Rice Nuker said:
The reason that half the fan is exposed out of the shroud or in some cases the shroud has the fan outer edge exposed on the bottom half, is that the fan is not only axial flow but centrifugal / radial and allowing the air to spill off the rear half of the fan radially allows it to expel considerably more volume of air from the shroud plenum.
Click to expand...

Yep, exactly.
 
Well thank you for not making feel like an idiot. I looked online and could not clearly find an answer. One more question Is it possible to roll a circle without a roller? If so any suggestions on how would be awesome. Ohh and reason to not pop rivet the corners?
 
..the only stupid question is the one that isn't asked.
if the fan is outside it will draw air in from the side where the air is not restricted, rather than pull it through the rad from the back
 
jhdeval said:
Well thank you for not making feel like an idiot. I looked online and could not clearly find an answer. One more question Is it possible to roll a circle without a roller? If so any suggestions on how would be awesome. Ohh and reason to not pop rivet the corners?
Click to expand...

No reason at all that you can't use pop rivets.
Just be sure none on the ends of them are rubbing the radiator anywhere.
You can use that sticky foam insulation strip stuff between them for sealing.
As far a rolling a strip of steel, it might be worth having it done by a shop with a roller.
I'd be tempted to do it by hand, but not really sure how to make it nice and evenly rounded.
 
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