# To use a cyclone or not



## ChrisBarrett (Jul 4, 2015)

So I have been piecing together my dust collector for my garage shop. So far I have a Leeson 3hp motor with a dayton blower. It pulls 1040 cfm right at the inlet with no ducting. My plan is to run 6" ducting to all the machines. I also plan on venting it out the wall.

Given the fact that I am not using a filter inside the garage, does it even make sense to use a cyclone? i could build an enclosure on the outside of the wall with 3 hepa furnace filters and a box underneath to catch all the heavy stuff…

I suppose this could cause some wear on the impeller, which is aluminum, as it would be pulling all the debris through the blower as opposed to all the heavy particles being pulled down by the cyclone.

Anyone have opinions on this?


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## splintergroup (Jan 20, 2015)

I have thought about directing the output air from my cyclone thorough the wall (no filter). The cyclone would catch the vast majority of the dust and chips and only the occasional stray flake would make it outside. Of course, this is greatly dependent upon where you live and how much you want to annoy your neighbors. My cyclone filter usually stays quite clean, but on the not so rare occasions I forget to dump the barrel, the filter gets a healthy coating of fine dust which really reduces the airflow. Eliminate that filter (and remember to empty the barrel), everything would be golden.

In your case I'm guessing two things. Either you don't want to lose the space eaten up with the cyclone/filter in the garage, or you are considering just dumping the output from your blower directly to your filter box in the great outdoors (no cyclone).

The cyclone/filter outside would be good since you can regain the lost space and still collect/stop all the dust and chips. Of course you will be expelling a large volume of air from inside your garage which will require an open window and reheating/cooling of the fresh air introduced for replacement.

Skipping the cyclone seems to me would quickly saturate your filters and just make a mess.


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## ChrisBarrett (Jul 4, 2015)

The space isn't too big of a deal, and I don't care much about losing conditioned air because it's not conditioned :-D I'm just wondering if my idea of building a "filter box" outside the garage that the DC empties into would even work. If I understand your reply you're thinking that even those filters would fill up pretty quickly so I'd lose efficiency that way.

Really my goals are two fold: lower cost and keeping up the CFM of the collector.

*edit* regarding my neighbors, I don't have any close enough that the random fine dust would bother - the noise might become annoying for them. The DC kind of drones, from the few times I've turned it on. I don't know how much of that noise will be translated outside.


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## joey502 (Mar 30, 2014)

If you add a cyclone then you do not need the filters or collection box outside. There will not be enough debris left after the cyclone to worry about collecting outside.

I added a super dust deputy to my dust collector over a year ago and have not yet needed to clean the filter.


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## ChrisBarrett (Jul 4, 2015)

Any ideas/numbers on how much a cyclone cuts down on efficiency and cfm?


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## JeffP (Aug 4, 2014)

I think if the exhaust is going to be outside a true "cyclone" is definitely overkill.

OTOH, a dirt-cheap separator is still a good idea to help you better coral the majority of the waste.

I made one last weekend out of a standard large metal trash can. Just cut a couple of 4" holes in the lid to insert a pvc elbow and a short straight pvc coupler. The elbow is positioned so as to spray the stuff coming in along the perimeter of the can, and then the exiting air comes out the center-mounted straight connector.

It works ridiculously well. Even gets the majority of the "fine but not invisible" dust. Good chance there is still a significant amount of too-small-to-be-seen dust at the exit, but I have no way to measure it.

Both my DC and its exhaust will be outside when I'm finished. Cheap, quiet, functional waste handling and dust reduction. The remainder of the dust remediation will be via a ceiling mounted air cleaner.

Anyway, my separator cost me all of $25 and a couple hours of work. Well worth it I think.


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## crank49 (Apr 7, 2010)

> I think if the exhaust is going to be outside a true "cyclone" is definitely overkill.
> 
> OTOH, a dirt-cheap separator is still a good idea to help you better coral the majority of the waste.
> 
> ...


You made it as good as it needs to be.
This setup would only reduce the available static pressure about 1 1/2" to 2".
A true, high efficiency cyclone could reduce your available pressure by 6" to 12" or more.


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## ChrisBarrett (Jul 4, 2015)

Okay can someone explain to me the static pressure measurement? Is more static pressure good, bad?


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## wapakfred (Jul 29, 2011)

SP is a measure of drag (resistance to air flow) on the system. As the number grows, so does the resistance.


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## ChrisBarrett (Jul 4, 2015)

So a Thien baffle, for example would add less static pressure than a cyclone but also allow more dust to go through? So you'd have a more efficient DC in terms of air flow but less efficient pre-filtration.


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## wapakfred (Jul 29, 2011)

I'm not sure what the difference is between the 2. Crank may have something, I'm sure there is a difference, but there are so many variables I'd think it would be a little hard to quantify.


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## toddbeaulieu (Mar 5, 2010)

I ultimately plan to vent outside. My barn is heated in the winter so my plan for that is vent it back into the barn during the winter. For that I will need filters outside and a simple "window" for the filtered air to be forced back inside. For the summer I could eliminate the filters and close the window.

As for cyclone, I think it makes a lot of sense to shield the impeller from large debris. Sooner or later you're going to have to deal with the pile outside and the cyclone helps with that, as well (bin).

Not smart enough to get into the scientific debate. A while back I read through all the Pentz material and simply got overwhelmed. When it comes time to upgrade my DC I hope to avoid getting hung up on splitting theoretical hairs. 3HP is a good amount of power and I question the value of stressing about these (assuming) minor factors. This is, of course, my own unscientific opinion. My crappy Reliant just barely meets my needs and I can only imagine what doubling the HP would give me.


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## Bill7255 (Feb 23, 2012)

I will give my opinion based on my experience. Nothing scientific, just based on what I have done. Comparing a Thien baffle to a cyclone the Thien does very well, but falls short if you have a drum sander. A cyclone far exceeds the Thien in this area. I can't really compare the loss as I have never run a back to back text to see what the effect is. I do believe going to a 6" main keeping the 4" drops as short as possible is significant. The other big factor is how well you collect the dust at the source. I am very happy with my setup. I went from a Thien baffle to a cyclone, and I am able to vent outside. It is a big plus not having to clean filters after using the drum sander. Here is a link to my setup.

http://lumberjocks.com/topics/117834


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## splintergroup (Jan 20, 2015)

> Really my goals are two fold: lower cost and keeping up the CFM of the collector.
> 
> - ChrisBarrett


I wouldn't worry then about a cyclone if you send the air outside. 3HP should move plenty of air, even for several wood chip producers running at the same time. Outside, you probably could get away with some form of a large box/bin around the vent to generally contain the dust, but beyond that any filtering would be overkill.

Inside, the cyclone helps keep the filter clean, which helps keep the airflow up.


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## shawnmasterson (Jan 24, 2013)

this is my setup. You could make a barel like the first one on my setup. as to venting it outside, I see you are in WI so you don't work out there in the winter?? because if you use wood heat then venting outside is never going to happen in the winter. you will back draft the stove and smoke out your shop.


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## ChrisBarrett (Jul 4, 2015)

I'll work in the winter, but not a whole lot. I use infrared and a propane convection heater. Heating the air has proven to be ineffective so far, so I just heat me and whatever i'm working on.


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## crank49 (Apr 7, 2010)

I'm going to try to explain static pressure without getting technical.

All pumps, including fans, do two things that each affect each other. They move a volume of something from one place to another and they do this by creating a pressure difference between the two places.

If you create low pressure in a certain place, then the surrounding air will rush in and try to balance the pressure. Suck the air from around a spinning saw blade and surrounding ambient air will move into that space.
The smaller the opening you try to pull the air through the faster it tries to move; at least up to the point there is not enough pressure to make it go any faster.

The higher the pressure difference the fan creates, the faster the air moves in to replace what's now flowing throught the duct toward the fan. This is important because the speed of the flow has to be at least as great as the speed of the dust and chips being thrown out of the saw kerf for the dust to get captured.

Whether the fan is positioned before the filter, or after the filter (or separator) make no difference to the relationship between flow and pressure. It is, very wise to put the filter or separator befor the fan to save wear and tear on the fan itself.

You can build a very simple gage to show the pressure available on any fan. It's called a u-tube manometer. You need nothing more than a few feet of clear tubing and a drill and some water. Look it up on Google or similar search engine and you will find tons of examples. Suggest looking for DIY u-tube manometer.

Caution, a shop vac based dust collector might produce pressure of over 90 inches of static and will suck the water out of your tube unless it is over 90 inches tall. Better to buy dial type pressure gages for these.


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## ChrisBarrett (Jul 4, 2015)

Crank, so is more static pressure in a system a good thing or bad thing? Or is it neither? Does more static pressure mean less CFM because there is more "suction"?


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## crank49 (Apr 7, 2010)

Sorry I took so long to get back. Been working 16 hrs a day.
Static pressure is a relative thing. 
Take a 1 1/2 HP dust collector for instance and measure the pressure near the fan inlet while the duct is just connected to a large open hood and you will see a number. Might be 4" pressure for instance.
Now connect the same duct to a close fitting shroud around a saw blade and that pressure might jump up to 8".
The volume of air being moved through the duct will be less with the higher indicated pressure, but the higher pressure means the speed of the air passing through the restricted shroud is faster.
The whole thing is a balancing act and the physics involved is pretty detailed but not hard to do.

You can envision the same principle with a hose pipe. When the end of the hose is open the water comes out and drops to the ground pretty quickly. Put a small nozzle on the hose and the stream of water becomes a high speed jet and goes much farther.


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## JAAune (Jan 22, 2012)

I'd recommend a cyclone for the long-term ease of use. It's true that if you vent outside after going through a high-efficiency cyclone you'll never be able to see visible dust coming out the vent. Never having to clean or replace filters will save time and money over the long run.

3 furnace filters isn't enough for a 3HP blower anyway. I've got over 400 square feet of filter area on my 3Hp cyclone and may increase that to a 1000 when I have more money to spare on that upgrade.


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## ChrisBarrett (Jul 4, 2015)

Yeah I'm kind of swinging back towards the cyclone, haven't made up my mind yet though. I still have finishing to do in the garage before I get to it.


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