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Old 06-01-2010, 11:23 AM   #12
is One Chatty Farker
Join Date: 04-14-10
Location: San Francisco, CA and Phu Quoc Island Vietnam

Originally Posted by BruceKWHP View Post
I have not held a BBQ Guru / pit viper fan in my hand. It is rated at 10 cfm and looks like a molded plastic fan / housing inside a sheet metal cover with a sliding damper door on it. Am I close to being right?

Or is it made of metal, with metal fan blades? I was reading about one of the fans (for a Stoker I think) that had a plastic fan blades and a flap door to protect it. The flap door swings open with airflow.
OK, I humbly stand corrected. I did a full strip down of the pit viper unit this morning and it does indeed have a plastic bladed fan on the interior with the exact same form factor as the digikey one posted earlier. PM me if you want the exact model. The fan blower is a squirrel cage type arrangement with 50 or so miniblades. So any "magic sauce" in the pit viper design is not the fan. Instead it comes from the stainless shroud and machined aluminum output port. These parts do a few important things:
1. Act as a rigid chassis with limited protection from the elements
2. Enable control of the fan output rate
3. Enable easy adapter design and quick release from the adapter.
4. Dissipates heat from the cooker before it hits the fan.

If I were to take a stab at fabricating this (I'm no fab genius) I would use thin stainless stock. Next I would:
1. Cut and bend a squared off taco shape to hold the fan unit and drill holes to bolt the fan unit into it.
2. Cut a rectangular end plate with a round hole in it for the fan output, weld this to the squared off fan output end of the taco, and seal the square fan output to round metal output interface with some type of non-permanent sticky adhesive.
3. To get the air to the cooker and dissipate heat I would weld a 2" length round stainless stock onto the end of the round hole.

Adapters would have to be fabricated per your cooker design. All could contain a round input nozzle to connect to the output nozzle on the fan shroud. To make the two round stocks interface snugly, one could create two grooves that go all the way around the housing output nozzle that could accept a silicone o-ring and size the round stock on the adapter to seal well to these o-rings.

For Weber kettles or WSM the adapter is a bit tricky as you need a way to snug a piece of round stock to one of the holes in the daisy wheel. To do this I would take the 2" round stock, weld a very small flat crossbar to the center, and tap/drill it to accept a long threaded screw. That screw then could then be used along with a large wing nut and bolt to tighten it against the weber.

Adapter would be cake for the BGE. All you need is a rectangular stainless piece that fits into the damper slider with a welded on round stainless output nozzle that interfaces to the round output nozzle on your fan chassis. To make the adapter snug to the cooker, you would use a super thin stainless wrap around shim on the top or bottom of the damper slider that would be pushed up once you had it all the way slid onto the damper track.

The only things these quick ideas don't address are fan output rate control. I'll have to think more about that.

Thanks for humoring me on this little rant.
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