# Rectanglar Dust Separator



## bomisore (Jun 27, 2010)

I love my Harbor Freight Dust Collector, but I hate changing the lower bag on the unit. This is mostly due to my laziness and the cost of the bags. The easy solution to this would be to add a dust separator. My issue with that solution is space. I have a small shop and have 19" of space between my bench (that is another project I have yet to complete) and my DC to where it would go. My solution to this is to make a box from MDF, that would be 18"W, 24" L and 38". The front of the box would be plexi-glass or another transparent material to allow me to see when it is getting full.

My question is, does having a rectangular structure change the air flow to enough to not make it worth it? I am not sure if I would get the air flow I would need. Below is picture of what it would potentially look like. My current thought would be to have the in feed and out feed mounted in the lid and have clear drum lines for easy cheap clean up


From Woodworking

Here is the product I would for the infeed and outfeed lines:
http://www.rockler.com/product.cfm?page=25225&source=googleps&utm_source=GoogleBase&utm_medium=organic&utm_campaign=Google


----------



## dq2 (Sep 21, 2010)

Sounds like you have a good plan in mind. The idea is to have gravity work for you so the big stuff drops out before it gets to the DC. I find no air flow problems unless I have a long run.

I made a separator out of an old garbage can, but after seeing your link to the Rockler plan, I think I will build a box for under my planer. Sure looks a lot easier for cleanup than emptying a big garbage can.

Thanks for sharing.


----------



## NBeener (Sep 16, 2009)

My understanding is … that a "drop box"-what you're talking about-is old school, and pretty common.

If you're a FWW online subscriber, take a look at this article:

http://www.finewoodworking.com/fwnpdf/011117066.pdf

And an article with more discussion on the topic:

http://www.woodweb.com/knowledge_base/Setting_Up_Dust_Collection.html


----------



## JoeLyddon (Apr 22, 2007)

I have a Dust Deputy to a Ridgid shop vac…
... It really works GREAT!

The principle is the same… I think the circular cone would work better… All of my hose connections and internal holes are never smaller than the main hose.

Any vacuum source can be used… all you'd have to do is connect it in series in place of your rectangular unit.


----------



## bomisore (Jun 27, 2010)

I have a Dust Deputy and it works great with the shop vac but the 2.5" hose would slow down and restrict the air flow. Also my jointer and planer would fill that very fast.


----------



## JoeLyddon (Apr 22, 2007)

How big is the hole in the horizontal separator piece?


----------



## bomisore (Jun 27, 2010)

Joe,

Large enough for the 4" fitting.

http://www.rockler.com/product.cfm?page=25225&source=googleps&utm_source=GoogleBase&utm_medium=organic&utm_campaign=Google


----------



## DaddyZ (Jan 28, 2010)

Ideas !!! Sweet Ideas !!!


----------



## JoeLyddon (Apr 22, 2007)

Oh, it didn't look that big to me…

If your planer & jointer would fill a 5 gal can FAST, your proposed system doesn't look that much larger… wouldn't it fill up pretty fast?

What do you use the Dust Deputy for?

Why not use a fiber drum as shown in the Rockler Ad of the link you posted? That looks like it would really do the job better than what you're thinking about.


----------



## bomisore (Jun 27, 2010)

My design is to do the best with the space limitations I have. The box would be 18"Wide , 24" Long and 38" high. The box design is not as large as a drum but that size will be should be sufficient. I have not found a drum that could fit in that space well.

I dont really use the Duty Deputy any more, I use the shop vac for cleaning the shop, since I have a DC now.


----------



## b2rtch (Jan 20, 2010)

Don't you need to have the spiral flow of the air stream and the centrifugal force to separate the heavier particles?
I do not think that square box would work well.
My 2 cents.


----------



## bomisore (Jun 27, 2010)

Bert,

I am not sure and have been looking for answers, do you have any suggestions?


----------



## JoeLyddon (Apr 22, 2007)

After studying it a little more, I think Bert has a good point.

I take it the TOP is the input and the bottom the Output…

I see the top section getting filled to the point where it does not hold anything back anymore and everything just goes directly to the bottom hole… I don't think it would get half full before it happened.

I think I would take the Dust Deputy idea of the cone, etc. and building something like it instead.

It wouldn't cost you much to try it… to find out…


----------



## bomisore (Jun 27, 2010)

Joe,

The air infeed and outfeed would both be in the top of the box. From some further research I have done, I would need to have a baffle between them to aid the heavier material in staying in the bottom. The idea is not much different from the drum, except its a rectangle.


----------



## b2rtch (Jan 20, 2010)

" The idea is not much different from the drum, except its a rectangle." 
I disagree with you.
I have been working around cyclonic cleaners for quite a few years, the first were on Farr air filters on heavy construction equipment over 30 years ago, and I always saw the whirlpool or circular flow of the air or gas or even liquids as creating or helping the separation, by centrifugal force, of the dirt or dust or heavier material.
At the same time there is a reduction of the flow velocity( as the flow goes from the wall/outside of the barrel or air cleaner to the center, the distant to travel decreases , decreasing the air velocity) which force the heavier material to fall to the bottom of the cyclone or can. 
In your design you achieve neither one of the two effect.
Your air velocity remains constant as well as the air pressure, so the dust and chipping will remain suspended in the air flow and you will not achieve a good separation if any at all.
I fail to see how this design could effectively work.
You certainly can try your idea and you might have some results but I doubt that they will be as good as with a barrel or a round shape.


----------



## bomisore (Jun 27, 2010)

Bert, 
I do not pretend to be an air flow/dust collection expert. I just want the wood chips in the box. I do not believe this design will be as efficient as a cylinder shaped unit, but I do think a rectangular box will get the job done. Please see the article NBeemer posted above. I appreciate your insight, I want to make the best separator I can.


----------



## childress (Sep 14, 2008)

This is the separator I made…Works great. Even with the "mini" blower it's works surprisingly well. And Bert is right about the whirlpool flow, I can see it in the clear hoses…


----------



## crank49 (Apr 7, 2010)

A dropout box does not have to have cyclonic flow to work. In fact, cyclonic flow increases pressure drop. High pressure drop is a good thing if you are looking to have high effeciency of collecting fine dust. But, if your system is borderline for having enough fan pressure in the first place, then you don't want to try to collect all that fine dust in the first stage; let it flow through to the bag or cartridge.

I assume the picture is a top view. The inlet could be aimed more at the bottom of the box. The baffle needs to be more open between the two halves of the box, and the outlet could be aimed more at the bottom as well. You don't want to restrict the area between the two sides of the box because that just forces the flow to accelerate between the two halves for no reason. In fact, it would work best with a baffle sealed to the top and extending about 1/4th of the way down, between the inlet and outlet pipes, and with one big open area at the bottom. Air comes in and flows toward the bottom while slowing down (largest area) and then has to reverse direction and accelerate back up the other side to the outlet pipe. The dust, chips and trash drops out of the flow during the turn and re-acelleration part. That's why it's called a dropout box.


----------



## MikeGager (Jun 15, 2009)

just try something like this. it only adds a few inches of extra footprint beyond the stock HFDC set up. the trash can contains a thein seperator and it works great


----------



## FirehouseWoodworking (Jun 9, 2009)

Good discussion on everyone's part. Good scientific points well made. However, one must put principles into context to properly examine pros and cons.

No argument here about cyclonic separators.

However the cons of the square drop separator have been perhaps overstated. The drop box works best when it it basically at the source of the sawdust and chips, just like the plans show, right under the planer. The pressure differential is sufficient to do the job at that point.

Of course, any other outlets between the drop separator and the vac/DC don't receive the benefit of the drop separator, so you have only solved a part (albeit a significant part!) of the problem.

Further, if you place the drop separator nearest the vac/DC and then run piping or hoses out to the tools, you will experience a significant loss in power at the various tools.

Me thinks that about sums it up. Good luck.

Cheers!


----------

