Need Blower Design Help for Wood-Burning Stove

[FONT=&quot]This is not your normal HVAC question, but I figured you’d be most qualified to help me design what I need.[/FONT]
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[FONT=&quot]I have a FABCO Signi-Fire wood burning stove (the company no longer exists). I find the fans to be too noisy, so I want to replace them with blowers. There are 7” holes with 3 ¾” space below and 5 ¾” space above. The motor needs to be installed below, or it will get too hot, and I was thinking of extending the shaft of the motor and attaching a metal squirrel cage with the open end facing downward. I’m not sure if this needs to be surrounded by a case or if it will pull air without being enclosed. This is the opposite of most squirrel cage assemblies, as they would have the motor in the heated area. I’m not sure if the squirrel cage should be slightly under the diameter of the 7” hole, fitting slightly below the opening or if it should be larger and fitting above it. I’m thinking a bearing supporting the motor shaft above the squirrel cage would be helpful. I’m attaching photos, diagrams and information from FABCO and would appreciate any suggestions you may have. Due to the fact I need 4 of these fans, suggestions for locating used/surplus parts would be appreciated, also.[/FONT]

Welcome to the site.
If you can run a round duct to the intake side, consider an inline exhaust fan like one of these.
http://www.amazon.ca/s/?ie=UTF8&key...vptwo=&hvqmt=b&hvdev=c&ref=pd_sl_3x5peflfl9_b

There is no room to run any of those, and I'd still be replacing a fan with a fan. I'm wondering if a squirrel cage would be quieter than a fan.

Someone could likely write a couple books with stuff I don't know about fans.
But I do know that the effects of air in a confined space can be noisy. A very quiet bathroom fan can be noisy if it is ducted with to small of a duct.
I doubt if a cage will work without a shroud as I think they work on centrifical force.
I don't think you can slow the motor, I think I would look at changing the fan it self to one that is less agressive, moving less air may lower the noise level.
Dirt on the fan blades can also increase noise.
I went looking to see what I could find and found this interesting.
http://physics.stackexchange.com/qu...-fan-blade-actually-does-the-noise-generation

Thank you for your response. It looks like I'm stuck with noise. I am able to slow the motor with my fan controller... As the power is reduced, the speed is reduced. Maybe it would be helpful to find a way to insulate the back of the door. It is a metal door with 1/4" glass exposed to the outside and a thin sheet of metal on the inside. Would any of you know of a material that could be applied to the inside that could handle the heat of a wood-burning stove? There is a dab of silicone adhesive holding the glass at the top. Maybe applying more silicone all across the top might help, also. The motors are old and showing their age, so I purchased replacements to use. Here is the spec sheet on the new motors: http://www.electricmotorwarehouse.com/PDF/Bulletin_6029B.pdf

I'm still hoping someone will pop in with some better ideas.

Install a remote fan in the ductwork somewhere else. We do this all the time. That way your not listening to the fan in the room with the heater. Its in the basement or attic and has an insulated cover.
We do this with wood and pellet stoves when one room gets too hot, Install some insulated ductwork and an inline fan.
Just another Idea.
Get a decent fan like this...http://www.ebay.com/itm/NEW-10-Inch...-Fan-Air-Vent-Blower-Heat-MK-10-/270987929996

I actually have the SFK for these units connected to my FAU, but I seem to lose too much heat in taking it to the FAU and then distributing from there. It might have made sense to just connect it to ductwork leading to the bedrooms when I was building my home, but I'm not going to tear it apart and run it now that the house is completed. That would require me cutting open the drywall above the wood-burning stove and running new ductwork into the attic (I'm on a concrete slab) and wading through the deep insulation... not going to happen. Thanks for the thought, though. You can see the SFK option discussed in the paperwork I attached above. I think the best solution will be finding the right insulation for the fan compartment doors.

They usually just use air between sheets of steel, find something to stop noise and can be in a hot zone may be tricky.

You mentioned the fans are getting old. Is it bearing noise? Have they always been noisy? Maybe just some parts need replacing.

Neal, that looks interesting. I sent an email to the manufacturer and will see if they have something that will suit my purpose. The problem will be that this company is in Australia and I'm in California, so shipping small panels may not be cost effective. I'll have to continue researching to see if I can find a local source.

Slownsteady, as I mentioned, the motors are showing their age, so I have purchased replacements and wait for them to arrive next week. The new ones are AO Smith's 9208F2. I'll be using the original nylon fans. The noise that has always bothered me was the sound of the fan blades cutting through the air at higher speeds. I am hoping to reduce that by experimenting with tubes as cowls around the fan, along with insulation behind the doors. I'm open to other suggestions people may have, also.

Fans cut the air and make noise when the air can't move fast enough. Here is deal on fans and how they function.
.http://www2.basf.us//PLASTICSWEB/displayanyfile?id=0901a5e180004891

Thank you. I found the information to be very helpful.