Drop slot on Thien Cyclone Separator Lid?

[tvman44]

I am building another Separator lid to be used just for my down draft portable sanding table and router and plan on making the drop slot 3/4" wide instead of 1 1/4".  Would that increase collection of fines, or be too small?  I know 3/4" is small but there will never be anything large going in this one, just sanding dust and chips from router.

[phil (admin)]

It will improve separation but I'll just warn that the flour we get from sanding is a challenge, even with conventional cyclones.

[tvman44]

Yep, familiar with the flour problem as I already have 2 of the Thien style separators, but have a
1 1/4" drop slot on those.  Wanted to try a smaller one on this one, in fact I made it today and if I don't like it I can always widen it.

[retired2]

I guess this is more of a question than a statement.  It seems the high air velocities required to keep coarse waste entrained for conveying becomes your enemy when you are trying to separate fines.  So, I would be experimenting with ways to reduce the air velocity in the separator.  The most obvious way is a larger than normal diameter.  Another idea is one or two strategically placed baffles perpendicular to the drop slot to intentionally create turbulance.

[phil (admin)]

I guess this is more of a question than a statement.  It seems the high air velocities required to keep coarse waste entrained for conveying becomes your enemy when you are trying to separate fines.  So, I would be experimenting with ways to reduce the air velocity in the separator.  The most obvious way is a larger than normal diameter.  Another idea is one or two strategically placed baffles perpendicular to the drop slot to intentionally create turbulance.

We need high enough velocity to keep the stuff against the wall, but we need a transition to a low enough velocity for it to fall.  Tough combo.

Maybe borrowing that baffle concept from the Department of Energy is the smart move.  This would force the airstream (and whatever is in it) down into the bucket.  So imagine a baffle that is tight to the wall nearly the entire circumference, but has a 1" or 2" notch and a ramp that hooks whatever is meandering against the wall.  You wouldn't want the hook to be too high, otherwise you'll get siphoning.

Thoughts?

[retired2]

I guess this is more of a question than a statement.  It seems the high air velocities required to keep coarse waste entrained for conveying becomes your enemy when you are trying to separate fines.  So, I would be experimenting with ways to reduce the air velocity in the separator.  The most obvious way is a larger than normal diameter.  Another idea is one or two strategically placed baffles perpendicular to the drop slot to intentionally create turbulance.

We need high enough velocity to keep the stuff against the wall, but we need a transition to a low enough velocity for it to fall.  Tough combo.

Maybe borrowing that baffle concept from the Department of Energy is the smart move.  This would force the airstream (and whatever is in it) down into the bucket.  So imagine a baffle that is tight to the wall nearly the entire circumference, but has a 1" or 2" notch and a ramp that hooks whatever is meandering against the wall.  You wouldn't want the hook to be too high, otherwise you'll get siphoning.

Thoughts?

That's another idea worth trying, and it might be worth trying the hooks with and without the current continuous slot.  My baffle idea was just some verticle obstructions, not too high, placed at several locations around the slot. 

I'm not sure if those obstructions would behave like your hook idea, or whether they would act more like a snow fence and dump the powder on the leeward side of the obstruction.  To extend the snow fence thinking, my obstructions could be perforated to allow some air passage at a slower speed.

I guess the difficulty with advancing these ideas is that, even if they hold promise, they are only of use in a separator that will be used exclusively for fines.  If you even accidentally sucked up some chips, you would have a very quick plug.

It's fun to "think out of the box", but you quickly get to the point where you gotta build a prototype to see if t holds promise, or if it is a complete failure.  Are there any drywallers here?

Hmmm....just had another thought Phil.  Your hook concept is going to push more air into the waste drum than with a conventional baffle.  For that air to go into the drum, there must be a place for it to return.  It would seem the place to vent the drum would be in the center of the baffle where the air is cleanest.  I'm not sure what the vent should look like, one large hole, or a bunch of small holes intentionally sized to somewhat restrict airflow, and control waste bypass.

[BernardNaish]

My Thien is a crude lash-up with the baffle pushed down into a plastic waste bin. The baffle is held in place by the slight downward taper and the spring in the walls. This bin has a series of indentations down the side to stiffen the thin and otherwise flexible plastic walls. Hence the air stream is forced against the wall and bumps along againsts this "rough" surface.

I have noticed that very fine dust ends up in the bottom of the collector. I have been so ashamed of my lazy build that I not mentioned this before. I checked today and indeed the very fine dust has been extracted. It looks as though this unintended structure might work for your sanding dust. The indentation are about an inch wide and 3/16 of an inch deep separated by a 1" wide smooth wall.

[retired2]

My Thien is a crude lash-up with the baffle pushed down into a plastic waste bin. The baffle is held in place by the slight downward taper and the spring in the walls. This bin has a series of indentations down the side to stiffen the thin and otherwise flexible plastic walls. Hence the air stream is forced against the wall and bumps along againsts this "rough" surface.

I have noticed that very fine dust ends up in the bottom of the collector. I have been so ashamed of my lazy build that I not mentioned this before. I checked today and indeed the very fine dust has been extracted. It looks as though this unintended structure might work for your sanding dust. The indentation are about an inch wide and 3/16 of an inch deep separated by a 1" wide smooth wall.

It would be pretty easy to take that a step further and simply build a separator whose inside wall is a washboard.  In fact if the washboard were angled down toward the drop slot that would incorporate Phil's idea of a hook.  However, that would complicate the fabrication.

[tvman44]

I would love to see a picture or drawing of the added baffle you all are talking about, as I cannot quiet wrap my head around the idea.

[retired2]

I would love to see a picture or drawing of the added baffle you all are talking about, as I cannot quiet wrap my head around the idea.

Without going to the trouble of mocking-up these ideas, let me try to describe what I think each of us was thinking, and for the sake of this description forget how each baffle would be installed or attached.  Here goes:

1) Phil's concept:  Imagine a sheet metal baffle - a full circle with no drop slot.  Draw a circle on the baffle 1" in from the outer edge.  That is arbritary, maybe it should be 3/4", maybe it should be 1-1/2".  Who knows?  We are in uncharted waters!  At some yet to be determined number of places, cut into the baffle radially from the edge until you reach the circular line.  Then continue the cut following the circular line.  Cut along the circular line in the direction of the air flow.  Stop the cut on the circular line when it is approximately 1" long (maybe 2") Now, bend this tab up 45 degrees.  So what you have is something that looks a little like a fin on a turbine.  How many fins are needed?  Who knows?

2) My idea:  Similar to Phil's, but the baffle would have a drop slot much like the current practice, but at some yet to be determined number of places, there would be a vertical tab.  I have no idea how high or how many, but I'd guess maybe three of four tabs 2"-3" high.  The tabs would be perforated with 1/4" diameter holes to allow air to pass through, but to be slowed down.  This is the principle that causes snow to drift on the leeward side of a snow fence.

3) Bernard's discovery:  He found that the ribs on his waste container partially produces the effect we are trying to achieve in the two ideas above.  So, I just built on the idea by suggesting that the ribs be exaggerated somewhat to improve the effect.  Here's one possibility.  Imagine a conventional top hat design with a normal width drop slot.  Now, cut wooden dowels to the height of the separator chamber.  Cut these dowels in half down their length, so that you have half circle dowels.  Attach the flat side of these dowels to the wall of the chamber directly over the drop slot so that you have a washboard.  Maybe, the dowels need to be shoulder to shoulder, or maybe they could be spaced apart at regular intervals.

Now the ultimate variation on this idea is if that washboard effect, instead of being vertical, were angled 30 or 45 degrees in the direction of the air flow.  That incorporates Phil's thinking from #1 above.  It slows the air, but also directs it into the waste bin.  The question of course is how in the devil do you fabricate something like that - vertical is easy, rotate it even a degree or two, and you have a real challenge.

[tvman44]

Ok, now I am beginning to get the drift.  Thanks.

[windy]

Anything such as corrugated roofing cut at an angle would work.

[retired2]

Ok, now I am beginning to get the drift.  Thanks.

O.K.  Now go build one of each and tell us how they work.  If they don't perform as advertised, I'm sure we can come up with some mods for you to try! ;D

[jnug]

Thanks.

I think I will try working on the air velocity first combined with a narrower slot. While trying some things there, I will likely work up a "fin" design as it sounds like the one that would be easiest for me to execute.

[retired2]

Thanks.

I think I will try working on the air velocity first combined with a narrower slot. While trying some things there, I will likely work up a "fin" design as it sounds like the one that would be easiest for me to execute.

Keep us posted!