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Dust collector separator -where do I place the outgoing hose: center or side? Above/below intake?

3K views 10 replies 6 participants last post by  MiniMe 
#1 · (Edited by Moderator)
The logic tells me that the outgoing hose should suck air from the middle of the vortex AND it should do it as high as possible since the dust and chips in the vortex have a descending trajectory These systems seem to contradict my theory. Why?

Th Lee Valley system sucks from the central point of the lid (vertical axis of the barrel)


Then there is the side option:


and then there is the very engineered Thien baffle thart also takes the air from the middle
 
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#4 ·
Already drilled my holes in the lid
Now the question is how low do I need/want to go with each (intake / outake)
I am seeing some videos showing the Thiem baffle where the air enters the baffle from the side at the same level with the intake which means it does not matter. If I want to install a baffle later then have to be approximately at the same level ..
 
#7 ·
http://www.jpthien.com/cy.htm

FORUMS:
http://www.jpthien.com/smf/index.php?PHPSESSID=6ea17c095b79d1a3e3916f754da9d7bc&board=1.0

From the legend s very own website. You ve got several days worth of reading ahead of you.

- Walker

I said PASS to that…I can live with some dust in the dust bag of my DC
I did find the website a while ago

- MiniMe
I only said pass because I got a super deputy. I did have a Thien before I got a DC. A separator makes life so much better. Less dumping and at least seems like less dust in the air. I also added a can filter off the outlet.

From what I've read, those lid separators are only ok. A Thien or cyclone drops more dust and chips before your outlet. I've used both, but not the lid, so only speaking from what I've read.
 
#8 ·
The Thien baffle really isn't that expensive, difficult, or time consuming to build.

Regardless, you asked about the science involved. The folks on the Thien forum have broken down every aspect of the build including placement/size of the intake and outtake ports, thickness of the baffle, width of the drop slot, depth of the chamber, you name it. They've tested, analyzed, posted results, adjusted and re-tested. If it's a science question you have, the answer is there.

I know it's a lot to look through over there, here is one thread that has a lot of good data:
http://www.jpthien.com/smf/index.php?PHPSESSID=ae51e4d1270f9fe74fc368c01e77ce6e&topic=563.0
 
#10 ·
Ok, some simple rules of thumb here.

1. You want the airflow to induce a cyclone in the container. The spinning airflow carries the particulates (chips, dust, etc) to the wall of the container where they start to drop out due to friction with the wall (on both the particulates and the airflow).
2. The slower the airflow, the smaller the particles that fall out of the airflow. So to get maximum separation you want the outlet to pull from from where the air is slowest, which in a spinning flow is going to be the center.

Most of the separators above are some version of the cyclone which use elbows, air ramps, etc to get the incoming airflow moving toward the wall of the container to help induce the cyclonic motion.

Best exhaust point is from the center as that is naturally the slowest (less particulate laden) air to pull from.

Everything else (and I mean that pretty literally) is a design choice impacting how efficient the separation. Round cyclones, conical, exhaust above or below the intake, etc all just contribute to exactly how much of the smaller particles get recirculated.
 
#11 ·
Ok, some simple rules of thumb here.

1. You want the airflow to induce a cyclone in the container. The spinning airflow carries the particulates (chips, dust, etc) to the wall of the container where they start to drop out due to friction with the wall (on both the particulates and the airflow).
2. The slower the airflow, the smaller the particles that fall out of the airflow. So to get maximum separation you want the outlet to pull from from where the air is slowest, which in a spinning flow is going to be the center.

Most of the separators above are some version of the cyclone which use elbows, air ramps, etc to get the incoming airflow moving toward the wall of the container to help induce the cyclonic motion.

Best exhaust point is from the center as that is naturally the slowest (less particulate laden) air to pull from.

Everything else (and I mean that pretty literally) is a design choice impacting how efficient the separation. Round cyclones, conical, exhaust above or below the intake, etc all just contribute to exactly how much of the smaller particles get recirculated.

- MikeDS
If I use an 90D elbow, can I count on the fact that after one complete rotation the particles will be on a lower spiral already and they won't hit the back of the elbow creating disturbances in the air flow and reaching the exhaust instead of heading down toward the bottom of the barrel?
If I use a 45D elbow I am afraid that the air could be directed toward the bottom of the barrel and stir up the alrea
 
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