I wonder if it would be possible to 'transplant' the motor & bearings from a quiet 120 mm fan to a 172 mm fan. AFAIK the existing 172 mm fans run at high rpm, deliver very high cfm, but are also very noisy.
If this 'transplant' would work, I would expect a ~600 rpm 172 mm fan to be about as quiet as a 1,000 rpm 120 mm fan, but move ~20% more air.
I know the 'transplant' wouldn't work for a long time, but if it would last long enough to perform noise measurements it would be, well... interesting.

172mm fan.....One hundred and Seventy two millimeters?!?!?!?!?!?

You shouldnt need a fan that big. If it was a 72mm i could see the point.
Whatever, it would be almost impossible to transfer the bearings due to differences in size and design life. It would be cheaper to get a new fan.

Not in general, but I do like the basic idea of home-made fans.

One possibility I can think of is if the 120mm fan hub is a bit smaller than the 172mm fan hub. In that case, it may be possible to gut the insides from the 172mm fan, and cut the fins off of the 120mm fan. Wrap the remaining 120mm fan hub with tape, and it could fit tightly inside the 172mm fan hub.

Of course, the 172mm fan won't fit inside the 120mm frame. You'd need to snip the frame supports, and either leave the fan without a frame or rig up something to attach the 172mm fan frame.

There are a lot of challenges here, to get it to work well...

Thank you, IsaacKuo, for the reply. I was however hoping to get an answer from one of the moderators.
I have a case concept with positive pressure, using two large fans (as large as possible) for intake, and no fans for exhaust. But no quiet extra-large fans to work with, so I came up with this idea of 'transplant'. In principle, by placing the hub of the 120 mm fan into the larger one of the 172 mm fan, the noise from the 120 mm fan motor may be damped a little.

I have done pretty much exactly as Isaac suggested to quieten down a squirrel cage fan and it worked a treat.


You don't have to be a mod to have good ideas etc.



Regards
Pete

I can see centering and balancing being a possible problem. IIRC some fans are corrected for balance at the factory, which complicates things.

There are 140 mm 1000 rpm Yate Loons but the only source I know about is in Germany,Silencio.

Tzupy
Imo, pressure is what you must care about, not flow. Try using 120x35\38 fans (they are usually clicky high speed screamers, so a transplantation of an L-type motor might be needed).