Thread: Blower exhaust ducting

I would not exhaust a dc/cyclone anywhere near any doorway that you wish to keep open. A dc/cyclone will create a negative pressure inside your shed and all you will end up doing is sucking the fine dust straight back in again. The exhaust should be as far away as possible from any door or window you ever wish to keep open while running your dc. The exhaust should also be downwind of any doorway.

I would also recommend not using 90deg bends even on the exhaust. My exhaust path is double "s" shaped but it is also 6 times greater in cross sectional area than the 6" pipe that feed it.

I thought suck/blowback might be a problem with the door option

I also just realised that I could optionally vent out via the floor of the shipping container but I'd have the same problem as trying to go out the whirlybird - the bends needed to get it pointing downwards without getting in the way or taking up too much room.

The exhaust is pointing across the container at about 45 deg which is making things a hassle too. I may have to look at changing the orientation of the blower so the exhaust is at 90 deg (or more) from the inlet so I don't have to have bends to get it venting in the right direction. At least that way I could keep the dusty in the back corner and could have a few low angle turns directing the ducting to the floor or up to the whirlybird along the back wall. I could also possibly use some flexi to go from the exhaust to the roof in one smooth rising line until it hits the whirly.

Hmm...I'm thinking out loud here, and this isn't as simple as I thought it might be. If only I could cut a hole in the wall of the container...this wouldn't be a problem...but noooooooo Ahh well. A bit more brain grinding is required me thinks.

Originally Posted by RedShirtGuy

The exhaust is pointing across the container at about 45 deg which is making things a hassle too.

That's easily fixed with a 45º bend. Is it that you don't want it in the way?

If you don't want to lose height, what about building a rectangular cross section duct that is only 3" thick but 20" wide - that'll be twice the cross section area of a 6" pipe and only half the height. Making the transitions will be a PITA but, HEY you've just built a cyclone!

The angle of the exhaust is just the way it ended up. Unfortunately I hadn't put much thought into the exhaust ducting when I put it together. If I can get away with a 45, that's better than trying to dismantle the top.

I'm not fussed about losing height. I just need a way to vent the fine stuff out of the container. I'll pop into Reece's or Plumbtec tomorrow (while I'm in town to visit the Wood Show ) and see what they've got handy.

No doubt that a lot of PVC connections will cost a pretty penny, so I'll keep in mind that I could make a rectangular exhaust section with MDF and gal/masonite/ply walls...which will also save me the hassle of doing a gal transition from exhaust to duct. I'd also be able to do much smoother curves. And if I was feeling *really* clever I could probably do both the turn back and a tilt up or down, depending on which direction I want to vent, all in one piece.

I'm still in two minds as to whether to vent out the whirlybird or go down through the floor. Both have their pros and cons. Although, I am leaning towards venting upwards as it takes up less room across the back wall, but at the cost of "muddying" the outside air with fine dust traveling at speed...how much do I care about the neighbors and their dangerously aggressive and incessantly barking mutt?

Thanks as always for the input Mr B.

All this thinking is 'exhausting'
*ba-doom tish*

Won't the whirlybird start turning with the exiting air? What's the escape velocity of a whirlybird?!? I made a sheet metal transition (square to round) and then used 2m of 150mm HVAC flex duct hose-clamped to that at the blower end, and to slotted, reduced and sleeved 150mm (now 150mm O.D.) stormwater PVC pipe at the other, which acts as a silencer (thankyou again Bill Pentz) as well as a convenient 'get out of jail cheap' go-round-corners duct. It's pretty smooth on the inside, compared to normal flex hose. Only about another inch of static pressure.

Yeh I'm not sure (yet) what the whirly is going to do when I shoot air up it. I don't even know if it's for bringing air in or letting it out. But I figure I'll deal with that when I get to it and possibly pull the stupid thing out to just run some pipe out of the hole instead.

I took to the cyclone with a pinch bar this arvo and with a huge effort managed to pry the top off (I guess I never expected to have to do that when I put it together originally) so I could turn the blower around to a more suitable direction for venting. It means I have to remake the top wooden bits of the cyclone - properly this time - but that has to be easier than mucking about trying to curve the ducting around. This way it should be a fairly straight and gradual rise up to the whirly with whatever piping I end up going with.

Originally Posted by RedShirtGuy

Yeh I'm not sure (yet) what the whirly is going to do when I shoot air up it. I don't even know if it's for bringing air in or letting it out. But I figure I'll deal with that when I get to it and possibly pull the stupid thing out to just run some pipe out of the hole instead.

I'm guessing a WB will just add unnecessary restriction to the air flow