Dust woes

[unitedcases]

So fellow carvers. Here is my dilemma. I have piped my dust collection outside my building. My dc is inside the building and the building is dustless. That part is great. Outside however is a mess. I need to wrangle the dust from going everywhere. I started with a box, that was absolutely no good. Then I got a big trash can and put an intake fairly close to the top. On the inside I put a 90 degree fitting that is turned at about 22.5 degrees downward to create a cyclone effect and I had a filter on top of the can with the lid holding everything in place, I put a 4in hole in the center of the lid for exhaust. The filter clogs up fast. so I removed the filter and stuck a thing of panty hose on the 4in exhaust coming out of the lid and dust blew everywhere and then when the panty hose filled up it started to move the lid. Even with bricks on it. Now I have my current config, I piped the original bag off the top of the dust can and the bag has so much resistance that it again is pushing the top of the can off. With bricks on it. Am I needing a more breathable bag and a better way to seal the can? I thank you for any help. The picture is of my current config.

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[cnsranch]

One idea, one comment.....

1. How about replacing the trash can lid altogether with some kind of cloth so the thing can breathe like a standard dust collector. Try a piece of cotton sheet as a test - I'm sure it won't trap dust like a 5 micron bag, but it's worth a try.

2. How are your winters? That thing is going to suck all the heat out of your shop in about a minute, and heat the great outdoors.

[unitedcases]

I tried a furnace filter over the top of it and that just cloggee after a few hours.

It doesnt suck the ac out. It is staying nice and cool in there.

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[bergerud]

It seems to me that the dust in your garbage can does not come to rest but keeps swirling around and so the finer dust finds its way out the top and into the filter. You may need a two stage garbage can. A cyclone part on top and a collector on the bottom. The dust has to fall into a place where there are no air currents. For example, if you cut a 4 inch hole in the bottom of your garbage can and made a funnel insert to fit inside (so the dust can fall through the hole under gravity) and then put that on top of a collector garbage can. Then the top can is the cyclone separator and the bottom can holds the dust. Does that make any sense?

[unitedcases]

What if I put a circular piece of wood in the can directly under the intake? Maybe put cutouts on the outside of the board for the dust to fall thru to the bottom. The board would probably be halfway down the can.

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[unitedcases]

Like this?

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[bergerud]

That maybe worth a try. Aim the elbow so it does not stir up the dust in the bottom.

[unitedcases]

I made a 20in circle and due to the construction of the can it naturally has slits on the sides to let the dust go thru. The filter I have for the top is heavy duty and washable so I washed it off. I will put it all back together tonight and give a whirl tomorrow. I have a 12 hr carve planned so what better way to test it out. Also the elbow is angled at about 20 degress so it isnt blowing straight down by any means.

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[bergerud]

The intake should shoot the dust as tangent to the can as possible so it swirls around the perimeter, slows, and drops. Bigger holes in the sides for the dust to fall through? Think that it is only gravity which gets the dust into the bottom.

[unitedcases]

I have no idea what you just said.

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[TerryT]

The intake should shoot the dust as tangent to the can as possible so it swirls around the perimeter, slows, and drops. Bigger holes in the sides for the dust to fall through? Think that it is only gravity which gets the dust into the bottom.

In a water vortex, particulates move to the center while spinning and the slower water in the center allows them to drop out of suspension. Wouldn't this vortex be similar? Slower air in the center of the vortex allowing the dust to drop out, rather than on the sides?

[unitedcases]

So drill a big hole right in the middle of the board and put a funnel in the middle?

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[bergerud]

In any vortex, the denser stuff moves out. The idea of the cyclone is that the dust, being heaver than air, stays on the outside while the pure air is removed from the axis. The dust on the outside falls down under gravity. (Usually the cyclone is slightly funnel shaped so that the dust keeps spinning as it falls but I do not think that is crucial.)

If the dust slows down before it falls or if the flow is turbulent, it can get to the center. Smooth flow is important.

By tangent, I meant that the dust should come in right against the side of the can and already be heading in the direction around the can. A straight pipe coming sideways into the can would be better than an elbow. I think that the elbow causes turbulence and may be a large part of the problem.

I hope some of this makes some sense!

[bergerud]

In a water vortex, particulates move to the center while spinning and the slower water in the center allows them to drop out of suspension. Wouldn't this vortex be similar? Slower air in the center of the vortex allowing the dust to drop out, rather than on the sides?

I have heard of behavior like this. Swirling tea leaves move to the center of the bottom of the cup. If that is what you are talking about, that is different. It has to do with the boundary layer and a secondary flow. The tea leaf example is actually counter intuitive since vortex behavior is opposite. Heavy stuff is thrown out.

[unitedcases]

I understand. Run the pipe in at an angle so it immediately throws the dust at the side of the can. I should be able to mod that side hole to accomodate that. Then do I just leave the baffle as is with the holes or slits in the sides? And one more thing, do not angle the intake at all, just straight in. Against the side of the can of course.

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[bergerud]

Check out this setup. It is called a Thien Baffle. This is sort of what you are doing. Get the intake pipe up against the side of the can so the dust blows straight around. It could be angled a little down to give the dust a downward drift. Maybe you can also move the baffle up some and make more room at the bottom.


http://i0.wp.com/s3files.core77.com/blog/images/2013/01/jphilthien01.jpg?resize=468%2C468

[unitedcases]

Going with what we got for now definitely. Been not carving trying to get this right and it is putting me behind. If this setup doesnt satisfy me then we will do that setup. I think I went to the same aite you did because it pulled up those exact same pics but it also had a list of exactly what to get. So this is my last ditch effort for the current setup. Thanks for the help. I will report later tonight with results.

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[bergerud]

I did not mean for you to abandon your setup and build the pictured Thien Baffle. I just thought the pictures might give us some useful ideas.

[unitedcases]

I know bergerud. No worries. So far so good. I put the pipe in and laid a furnace filter on top. Then put the lid on with a 4in hole cut in the center of it to vent. I think what I will do is at the beginning of every day I will just swap out the filter. It takes 2 seconds to wash it off and then it dries in about an hour. So I think for the most part it is licked. I would like to have a bigger filter so it would go over the lip of the can and be able to just use a bungie cord but it works for now. I may try my 12 hr carve tomorrow. Thats the real test. If it makes it thru that then I am a happy man. I dont mind changing the filter daily I just dont want to have to do it every couple of hours. The only thing that I did notice is with the thien baffle system their drop shoot is about 1 in. While mine is only 1/8 inch at best. All I am picking up is fine dust so I guess all we can do now is test it out.

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[unitedcases]

So far so good. Granted we are about 30min into a 11.5 hr carve. Will report more later. Just wanted to keep the thread at the top of the list.

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[cestout]

I had to remove my intermediate want ever you call it because I was losing too much suction. Now I run from the 2 CarveWrights (with a blast gat on each) to the DC. I sometimes use the intermediate thin when I hook the DC to a plainer - thickness of jointer.

[unitedcases]

Well the dust is falling into the bottom but the filter is still getting clogged so...I am going to add a top over the intake with a 4in hole in the middle of it. This will eventually be the spitting image of a thien baffle system. When I put that "top" piece in I will seal it down so the only way dust can escape is thru the small 4in hole and then there will be a filter to catch whatever escapes. Currently it is working well except I am having to changebthe filter every few hours. But the machine and building are still dust free so definitely worth all this trial and error.

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[unitedcases]

I did not mean for you to abandon your setup and build the pictured Thien Baffle. I just thought the pictures might give us some useful ideas.

@bergerud

Putting a bag on the top to have better airflow and better consistency for dust that slips upwards out of the cyclone. Do you think 1micron is too fine. Or that it may constrict too much?

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[bergerud]

I really have no idea. I have a simple little system where for months, no dust seems to get past my little cyclone. Maybe someone else with a larger system can answer your question.

[unitedcases]

I'm going to add the upper baffle right now and then tomorrow when I do a carve I will see it the bag is even needed. If the dust drops like it's supposed to then I may be done throwing cash at it.

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[unitedcases]

Just a little bump here. The thien baffle system is working. I have a bit of a weekly schedule to include dumping the dust garbage can out but it is working. The shop is dust free and I dont have a mess outside. I change the filter on the top of it about every 5 hrs depending on how full the can is. I just ordered some 5 micron material to make a bag from and that should keep me from the 5hr filter changes. No plans with it but if anyone is interested I can share what I did to make it work.

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