Scaling to 6" ducts

[charlton]

I'm evaluating my dust collection options and am considering a DC that moves between 1200-1600CFM. My understanding is that this normally requires 6" ducting. On the Phil's main cyclone page, he makes mention of a 2-4" in/1-6" out design. I'm wondering two things:

1. Is it reasonable to even try doing 6" ducting on the lid? I can certainly get drums/barrels that have diameters 18" or greater but a minimal lid design would require 6" + 3" (half of the diameter for the center of the lid) yielding an 18" overall diameter. Would putting the inlet port directly next to the outlet port be reasonable or would there have to be greater distance between the two? My blind intuition tells me that this is not really reasonable (the inlet port would almost instantly hit the drum wall due to the tight radius and debris would likely be picked up by the outlet port.

2. Given the amount of volume, would the slot in the baffle need to be made larger to accommodate the increased volume of air being moved?

The other option is, of course, to just make two cyclones each using a 4" ducts but that requires more shop space.

Thanks,
Charlton

[CheapScotsman]

I picked up a inexpensive 2HP DC off craiglist that supports 6" ducts so I, too, am wondering if a 6" inlet/outlet would be reasonable. I've snared a 22" wide fiber drum so, while I have a bit more room, it isn't much

I am probably going to do it the way boisejim did it in this thread: http://www.jpthien.com/smf/index.php?topic=65.0. It puts the 6" inlet on the side (pushing the inlet further away from the outlet AND it eliminates one pretty strict elbow which should improve CFM through the unit

[charlton]

Yeah, I saw that. There are two things that I'm not really certain about with a design such as that (as appealing as it is):

1. Taking out the trash means you'll have to take off the lid and the ducting that attaches to the bucket. My preference would be to leave everything on the lid so that it's a simple removal with minimal movement (lift the lid, cover up the can, and go).

2. Does the tubing at the side of the can actually protrude INTO the can or is it internally flush with the inside of the can? I would obviously prefer it to be flush but I'm not sure if that will cause the incoming air stream to bend towards the center. The debris will have inertia but I don't know if the air stream will stay tight against the wall.

I wonder if someone with good skills in Finite Element Modeling could actually model the behaviour. :)

Charlton

[CheapScotsman]

For your #1, my idea is to build a top that contains the intake, outlet and baffle ... and that top will sit onto of my collection drum so that it only need to be lifted <1" for the collection drum to be removed ... I need to learn sketchup

For your #2, in the 3rd photo on the link above above, you can see that the intake does NOT extend into the baffle area (it is flush with the sides of the drum). Whether this improves or doesn't the separation rate, I have no idea.

[phil (admin)]

Sorry for the slow response.

If you can pull it off, having a true side-entry 6" and a 6" take-off would be optimum.  Yes, it would work.  It really isn't very dissimilar to modding a single-stage DC's ring, when you think about it.

[CheapScotsman]

Excellent, thanks ... I am going to try the 6" intake into the side in the next little while.

Should the inlet tube extend into the baffle area or should it be flush with the side of the unit (as Boisejim did from this thread: http://www.jpthien.com/smf/index.php?topic=65.0) ?

[bennybmn]

I would make it flush, less obstruction in the airflow inside.

Have you guys considered, rather than a lid, make like a whole cylindrical ring, including the lid in one piece? Like 6 to 8 inches tall to accomodate the side entry 6" port, then the baffle on the bottom, lid on top, and it just sits on the top of the barrel. Like someone said, you'd only have to lift it a little to take out the trash. (Now that I think about it, I think that's what one of the above posters is doing...)  I could do a quick drawing if someone needs me to elaborate...

[CheapScotsman]

That is exactly the way that I've been thinking about doing it as I mentioned above.

PLUS .... mount the blower above the ring (like Robert did in this post: http://www.jpthien.com/smf/index.php?topic=27.0)

The blower will be fixed into position (cause its heavy) and I'll use flexible hose to connect it to fan to the ring/baffle outlet. This will allow me enough "flex" to disconnect the ring from the barrel and pull the ring up.

The output from the blower will go into into a Wynn style canister filter but one with an internal paddle that allows the filter to be "cleaned"

My idea is to laminate up to a 1" wide strip on the outside of the ring and the barrel so that I can use insulation (and a couple of quick release clamp things) to "seal" the connection between the barrel and the baffle (ring).