Dust Collection - Outside Exhaust

[John Akerblom]

Hi,

I am putting together a little workshop in the garage of a house I just moved into. I am running a TS, lathe, miter saw, and will be adding a bandsaw, a router table, and maybe have room for one other tool. I am trying to figure out the best way to collect all the dust.

My main concern is getting a powerful enough DC to actually suck up the dust from each tool (including fine particles). My second concern is cost (my budget is flexible, but I don't want to buy anything I don't need [see below re: external exhaust])

I noticed a lot of the issues on these forums have to do with a loss of suction due to filter clogging. I have a nice concrete space behind my garage where I am planning on building an MDF cabinet around the DC. I'll line the MDF with sound deadening insulation, and then create some sort of baffle to exhaust air efficiently while deadening the sound. I plan to run the intake PVC pipe through a hole I will cut in above the garage's rafters, then create a system of PVC in the garage to minimize the suction loss (6" ridgid PVC reduced down to 4" with blast valves at each tool [using a minimum of flexible hose]).

Therefore, since I can exhaust air (and fine dust particles) directly into my backyard, all I really need is a powerful motor, and some sort of cyclone/separator to collect the chips and thicker particles into a waste receptacle.

Does anyone have any good ideas on a good setup to operate within these parameters? Almost all of the ready-made systems I have looked at focus a lot on the filtration system, while all I really need is a chip collector and a powerful motor/strong impeller. Any and all guidance (and pointers to other threads that have addressed this) would be greatly appreciated.

Thanks,
John

[Julie Moriarty]

I have a Delta drum type dust collector that I modified into a cyclone DC. I've always exhausted outside. Before the cyclone mod, a LOT of waste spewed out on the lawn. Since the mod, all there is is some fine dust that vanishes in the wind. Here's the thread for modifying a drum DC to a cyclone: http://www.sawmillcreek.org/showthread.php?191422-Making-a-Cyclone-from-a-Drum-Dust-Collector

[Steve Kinnaird]

You mentioned building the walls out of MDF. Is this and enclosed area or outside?
MDF will not hold up to moisture.
Get a good 2HP or better DC.
Setup the cyclone separator and where the blower motor would normally go to the filter and collection bag, just direct it outside.

[John Donhowe]

There's a lot of good info on Phil Thien's site (jpthien.com) about effective dust separators. One thing to be aware of is that sound insulation material is also usually thermal insulation, so be aware that you might have a lot of motor heat buildup in your cabinet unless you provide good ventilation.

[James Gunning]

If you want proper dust collection from the start, the answer is a cyclone with a large enough motor and impeller and large enough piping (6" or greater) from your machine to the cyclone. Anything else is just an intermediate step on the way to finally getting the cyclone. Strongly suggest you look at Bill Pentz website and read the material there. http://billpentz.com/woodworking/cyclone/

Exhausting outside is actually the best way to handle the cyclone exhaust from the dust collection angle, but be sure you are allowing for the make-up air that exhausting outside will cause. You will be blowing out part of your heated or air conditioned air. Also, make sure you are not pulling fumes from a water heater or furnace into your shop.

[David Ragan]

If you want proper dust collection from the start, the answer is a cyclone with a large enough motor and impeller and large enough piping (6" or greater) from your machine to the cyclone. Anything else is just an intermediate step on the way to finally getting the cyclone. Strongly suggest you look at Bill Pentz website and read the material there. http://billpentz.com/woodworking/cyclone/

Exhausting outside is actually the best way to handle the cyclone exhaust from the dust collection angle, but be sure you are allowing for the make-up air that exhausting outside will cause. You will be blowing out part of your heated or air conditioned air. Also, make sure you are not pulling fumes from a water heater or furnace into your shop.

Excellent advise-all of it.

[Jim Andrew]

Before you buy a dust collector, be sure you look at the size of the impeller. The bag units typically have smaller impellers than the cyclones. The biggest bag unit is the 3hp Jet or Powermatic, same unit, with a 14" impeller. The Grizzly cyclone units appear to have bigger impellers than comparable units except for Clearvue. Some of the companies don't even post the size of their impellers.

[glenn bradley]

Ah dust collection threads . . . so much discussion, so much information :)

You are ahead of the game in that you have your desired end in focus. Many folks have added cyclone to systems not designed for them and have had some success. In high school folks would put V-8's in Volkswagon buses but, the drive train would fail somewhere soon after. My point being that if you are starting from scratch you don't have to try to make a non-cyclone blower work a cyclone. there is more science in air movement than I will ever understand but, we all know the old saying about the right tool for the job.

Your blower will match the cyclone it is designed for. If I were in your enviable position of being able to vent outside I would simply duct my current cyclone outside and skip the filters. I suggest yo do the same. Others will have many other opinions and suggestions :) .

[Dan Friedrichs]

I vent outside, and it's great (if you live in a climate that can tolerate the heat/cold loss - which is not as big of a problem as you might initially think). You don't even need a cyclone - a separator (like Phil Thien's design) is more than sufficient.

The noise issue isn't as severe as you might think, either. I'd highly recommend trying the blower to assess the noise level before you begin building an enclosure.

Acquiring just a blower/motor might be tricky - I'd recommend watching craigslist for a used bag-type unit, then just removing the bags.

As others have said, you are wasting capacity if you neck the 6" main lines down to 4" at the tool. The frictional losses in 4" vs 6" line are negligible - if you neck down to 4" at the machine, you might as well use 4" pipe throughout (assume you're a small one-man shop only running one machine at a time). And using 4" throughout is a horrible idea - so find a way to modify machines to accept a 6" port.

[John Donhowe]

if you neck down to 4" at the machine, you might as well use 4" pipe throughout (assume you're a small one-man shop only running one machine at a time). And using 4" throughout is a horrible idea - so find a way to modify machines to accept a 6" port.

With all due respect, I must disagree with these comments. There are two major factors in dust collection: air flow (cfm) and air speed (fps), and duct system design is a compromise between the two. Larger ducts reduce resistance to flow, to improve air flow, but the air speed in the duct decreases- air speed = air flow/duct area. You need about 3000 fps air speed to keep typical wood particles moving in horizontal duct, but 3800 fps to pull them vertically (as with most systems with duct drops from an overhead horizontal trunk). So, your blower might be able to produce 3000 fps in 6" duct, but the only way to get up to 3800 fps is to go to 4" duct to avoid clogging.

Also, running 4" pipe throughout is not the same as running 4" for a short length and connecting to 6". By analogy, running a short 16 gauge extension cord to a 12 or 14 gauge circuit outlet is not the same as running a super long 16 gauge extension all the way back to your electrical service panel.

There are many collectors that simply are not powerful enough to generate sufficient air speed in 6" ducts, so the only option is to use 4" in the whole system.

[Dan Friedrichs]

I agree, John - my statement was excessively generalized, and I'm assuming (perhaps wrongly) that the OP is looking at a 3-5HP collector, without any filters, which would be capable of supporting sufficient velocity in 6" pipe. My point was that for a ~5HP collector (what many would consider the "ideal" size), used in a home shop, performance from a system done with 6" mains and 4" drops is more similar to a system done entirely in 4" than a system done entirely in 6". I haven't done the analysis, but intuitively, I think for the lengths of pipe and air speeds we're talking about, the frictional losses are not significant - but since most users are seeking maximum CFM, the use of a reducer trades CFM for velocity, which is generally undesirable.

[John Donhowe]

On same page with you, Dan. :)

[Dan Friedrichs]

On same page with you, Dan. :)

I thought no one was allowed to agree on this topic :D

[William A Johnston]

John I just went through a similar situation. I took my 2hp single stage collector and modified it with a cyclone seperator from Saratoga cyclone seperator and vented outside. It works like a charm. I put gates at all machines and open as needed. Improved the performance is the system greatly. I have about $350.00 in the seperator and stand. I had the 2hp unit already. No more filter clogging or filter resistance.

[Allan Speers]

With all due respect, I must disagree with these comments. There are two major factors in dust collection: air flow (cfm) and air speed (fps), and duct system design is a compromise between the two. Larger ducts reduce resistance to flow, to improve air flow, but the air speed in the duct decreases- air speed = air flow/duct area. You need about 3000 fps air speed to keep typical wood particles moving in horizontal duct, but 3800 fps to pull them vertically (as with most systems with duct drops from an overhead horizontal trunk). So, your blower might be able to produce 3000 fps in 6" duct, but the only way to get up to 3800 fps is to go to 4" duct to avoid clogging.

Also, running 4" pipe throughout is not the same as running 4" for a short length and connecting to 6". By analogy, running a short 16 gauge extension cord to a 12 or 14 gauge circuit outlet is not the same as running a super long 16 gauge extension all the way back to your electrical service panel.

There are many collectors that simply are not powerful enough to generate sufficient air speed in 6" ducts, so the only option is to use 4" in the whole system.

I seriously question that last part, though I am so expert and you may be correct. The way I understand it, if the main pipe is sealed, then makiing t as wide-diameter as possible is ALWAYS better as this reduces pressure on your blower.

Since we're doing analogies, it's like sending water to a sprinkler head vias a 1/2" hose vs a 3/4" hose. That sprnkler's inlet diameter is the limiting factor, but a 3/4" hose will result in a much more powerful spray.

Analogy #2: When I clean the floor with my Festool CT36, I use a nozzle that has a 1.25" opening. I used to use the narrow hose that came with the saw, and which works well with my sander. However, switching to a 4" diameter hose made a HUGE difference in how much that nozzle sucks up.
I think that when the large diameter / low air flow chamber suddenly becomes a narrower outlet (from the tool, this creates the air speed that we need, and there's probably some math involved there. But again, my understanding is that the larger the main trunkline, the better.
If someone knows FOR SURE that this is incorrect, I'd very much like to know.

[Chris Friesen]

[/B]
I seriously question that last part, though I am so expert and you may be correct. The way I understand it, if the main pipe is sealed, then makiing t as wide-diameter as possible is ALWAYS better as this reduces pressure on your blower.

Nope. The issue is that you need a certain airspeed through the pipe to keep the dust suspended, and the required speed goes up on vertical runs. So if you make the pipe too wide, the dust will literally fall to the bottom of the duct and build up, giving unpredictable performance.

Now it's true that a 6" duct that narrows down to 4" for a short segment will be better than all 4", but only if the speed in the 6" duct is sufficient to keep the dust suspended. So your best bet is to modify tool hoods if necessary to get 6" ports on the tool. (Or multiple smaller ports, like two 4" ports or a 5" and a 3".) If you're stuck with a 4" port, you might want to open up another port near that tool to ensure there is enough airflow (in CFM) in the 6" duct to get the necessary airspeed (measured in feet/min).

One last thing...it's not enough to just put a 6" port on the tool, you have to make sure that there is enough opening on the tool for intake air to supply the air that's being sucked out. For example, don't go sealing up the tablesaw cabinet tightly, you need a certain amount of gap space for that make-up air to flow in.

[Allan Speers]

"The issue is that you need a certain airspeed through the pipe to keep the dust suspended,"


Ah, that makes sense. Thanks.

[William A Johnston]

John,

As you will see there is so much information on Dust Collection. I've read the a ton of blogs on here and on other sites. It can be very confusing, or maybe its just really confusing for me. I had an older Grizzly 2hp single stage unit and added a cyclone separator and vented outside. I don't have any way of calculating the CFM's but I have about 8 foot of 6" line then it drops to a 5" trunk line then to 4" at all my machines. I can attest that it increased my suction greatly. With venting outside you won't have any filters clogging or filter restriction. I have roughly $ 350.00 in the cyclone separator and the wood framing. At some point I will increase my trunk like to 6" and increase the size of my tool ports to either 5" or 6". My main killer on the old system was the drum sander.

Good luck with your quest.

Bill

[Allan Speers]

"The issue is that you need a certain airspeed through the pipe to keep the dust suspended,"

I'v been thinking about this problem a bit more. Time for some patented Speers "outside the box" thinking:


OK, so if the diameter of the trunk line is too big for a given CFM, your dust will settle at the bottom of the line and mostly air & super-fine dust will get to the impeller. I get this, no argument.

And yet, it's also true that no matter what motor & impeller you have, a larger trunk puts less strain on the system and will result in more CFM - It just won't be EFFECTIVE CFM. So maybe there's a solution: (maybe)


Idea #1: Use an 8" trunkline, but have a number of smaller-diameter junctions, to temporarily create a higher velocity stream of air. - Maybe one every foot or so. The idea is that these narrow ports would create enough localized air speed and turbulance to keep the dust suspended.


Idea #2: Maybe there's a way to mechanically "shake" the trunk line, thus keeping the dust from settling & allowing a slightly larger diameter. Perhaps this in conjunction with #1.


Idea #3: Put lengthwise "ribs" inside the extra-wide trunkline, then have a small motor slowly turn it, like they cook hot dogs at 7-11. Whatever dust settles would continuously get pulled to the top and dumped back through the air steam.

----------------

OK, I didn't say this would be easy. :( - but it might be better than my "turn your lunchbox planer upside-down and use it as a jointer" idea. :)

[Leo Graywacz]

I bought a Oneida 2 1/2 HP Super Dust Gorilla. I used it with the pleated filter for a couple of years. Then I plumbed it outside. Couple of things happened. The sound level was greatly reduced. The suction was increased and constant now. And the big one, if you let the barrel get overfilled it doesn't stuff the filter which takes 3/4's of an hour to clean out properly.

Disadvantages are it'll suck out the heat or cold when you use it.

http://www.fototime.com/5A10C7A60F01048/orig.jpg

[John Donhowe]

At the risk of hijacking the thread, I find your outside the box ideas interesting, Allan. The problem I see with all of them, though, is they all introduce turbulence into the system, and turbulence will absolutely kill effective air flow. That's why recommendations for DC layout design say to minimize anything which will produce turbulence, such as sharp pipe bends and abrupt transitions in pipe diameter or shape. If my mental picture of Idea #1 - looking like a hank of sausages linked together :D - is correct, my guess is that it would be more detrimental to air flow (cfm) than a straight, narrow, uniform diameter pipe.

One alternative that has occurred to me is to use an extra large diameter horizontal trunk, which will nor seriously affect air flow. Air speed will suffer, so saw dust will probably settle along the bottom of the pipe, but so what? (Let the chips fall where they may, so to speak!). Dust sitting in the pipe isn't causing any harm, other than risking moral outrage of those woodworkers like having their shop being perfectly clean. The dust is trapped in the duct, and not getting into the ambient air.

As dust accumulates in the pipe, the effective pipe diameter will narrow, and air speed will increase, until it reaches a point of dynamic equilibrium , where the airspeed is high enough to start pulling some of the settle dust into the air stream, and keep dust suspended.

This assumes that the weight of the dust wouldn't cause any structural stress on the duct, and also assumes there is no safety hazard, such as igniting settled dust by a static electricity spark. Just my own thought experiment... :)

[Dan Friedrichs]

Just want to point out that if you're venting outside, there is no need for cyclonic separation. The cyclone is useful if you have filters, as it get more of the dust separated out, reducing the amount that goes to the filters. But if you're venting outside, there is no concern about fine dust going out with the exhaust, so you really only need some crude chip separation. A separator is likely smaller, cheaper, and adds less resistance.

[John Akerblom]

To update, I live in Los Angeles, so heat/cold is not an issue. Also, I can crack my garage door to make sure the pressure remains constant. So far, the cheapest and best deal seams to be the Clear-Vue-Cyclone (Model 1800) with no filters. It is only about $1500 and includes a 5HP blower and 18" steel impeller. I plan on running 6" ducting along the garage rafters and then modify as many ports as I can so that I do not have to neck down (I believe the 5HP will move sufficient air to pull the dust up the 6" ducting). I may have to neck down to 4" for a few tools on the drop-downs when that cannot be avoided. I'll also have to build a hood for my new Nova DVR lathe (to at least catch the dust if not the large chips).

My last remaining issue is the volume. I live in a residential neighborhood and have nice neighbors. Ideally, I would like to build a little cabinet for the system behind my garage and then run the inlet line through a hole in the wall of the back of my garage. I was planning on using 3/4 MDF (potentially two layers) and then just throwing a coat of marine varnish on the whole thing (it rains about twice a year here). I could make some sort of baffle to allow ventilation to ensure heat buildup isn't an issue. Alternatively, I could build a cabinet inside my shop. However, I don't have much room, and the floor slab is so uneven I can't wheel things around easily so all my tools are shimmed up to level and not easily adjusted.

Another quick question, would this setup (assuming I use efficient joints in the ducting and a minimum of flex tubing) be sufficient to extract dust from a router table and miter saw? I have been reading a lot on these forums, and some people suggest that a shop vac (festool or fein) is needed for these small hose dust extraction scenarios.

[James Gunning]

John,

The Clearvue will certainly provide excellent dust collection and will work on pretty much all the tools you have. IMHO It's probably the best choice out there right now for a cyclone. Places where smaller hoses are needed can still be used with a cyclone, but the airflow would be reduced by the smaller openings. I have a cyclone that I use on the larger tools, but for things like a ROS, pickup from a hand held router, etc, I use a shop vac in connection with an Oneida plastic dust deputy cyclone. The airflow characteristics of the shop vac and the small cyclone (dust deputy) match the use of the smaller hose better than the larger cyclone. For a router table and miter saw the cyclone will work fine. The airflow problem can be solved by using two (or more) hoses wyed together and connected to the main 6" trunk line to insure enough air flow and get all the places dust and chips are generated. Example would be near the router bit in the fence, and below the table drawing from an enclosure surrounding the router. It normally wouldn't be practical to use 6" hose on the router table fence, but a 2" or 3" hose would work wyed together with another 4"-6" hose from the router enclosure. The miter saw could use a smaller hose from the blade shroud wyed together with a 6" hose from a shop built hood behind the saw. Your Nova lathe could use a large hood to catch much of what it generates. With a Clearvue cyclone pulling through a 6" hose if the lathe hood is well designed, it should catch nearly all of what comes off the lathe.

If you live in a residential neighborhood and you exhaust outdoors, you really want the cyclone to keep your shop from spewing chips out onto the lawns in the area. It will catch something like 98% of the chips and dust you generate. The rest is just very fine dust that will dissipate with the wind. Using an enclosure is wise as it will lower the noise level for everyone within earshot.

When I upgraded my DC, I went to 6" pickup hose. I have a small garage shop and move a portable DC to the tool. http://www.sawmillcreek.org/showthread.php?230817-Yet-another-dust-collection-post!-Portable-SDD-build The amount of increase in suction going from 4" hose to 6" was an eye opener. You may need to modify some of your tools to use 6" pipe, but if you use the "standard 4" you will choke the airflow the Clearvue will provide. Here is a look at some of the modifications I did to my machines. http://www.sawmillcreek.org/showthread.php?230820-Yet-another-dust-collection-thread-Adapting-the-machines-to-use-6-quot-pipe

[William A Johnston]

If your in a residential neighborhood are you at all concerned about the additional noise? The noise on mine is much louder outside than when my unit was running through a filter inside.

I assume this is common?

Bill

[Allan Speers]

If your in a residential neighborhood are you at all concerned about the additional noise? The noise on mine is much louder outside than when my unit was running through a filter inside.

I assume this is common?

Bill

True, but it's pretty easy to build a muffler out of MDF, 4 lb/ ft mineral wool, and something to waterproof it. (2-part epoxy paint?)

You just have to make sure the outlet isn't mechanically coupled to the wall. A small bit of rubber or foam does the trick nicely.

[John Akerblom]

I've decided to go with the 5hp cleavue in a waterproofed, muffled, mdf outside enclosure with 6" mains and drop downs. I can modify most of my tools to accept 6" ports or 2 wyed 4" ports. I'm sure I'll be able to cobble together some hoods. Thanks for all the input. Saved countless hours and dollars not having to reinvent the wheel.

Now ive got to design and buy the damn ducting. Lots of design ideas, but not much supply for pipe. 6" pvc pipe is expensive! Especially the fittings! Does anyone know a cheap online source? I figure sewer and drain pipes are the cheapest, but my nearby big box stores don't carry 6"

any and and all help, ideas, and suggestions are greatly appreciated.

Thanks,
john

[William C Rogers]

You need to check plumbing supply places for the sewer pipe. Not sure of your location, we have Furgersons in my area.

[John Akerblom]

Southern California, Los Angeles Area.

[Matt Morgano]

John,
The ductwork isn't all that bad once you find it. I hung all my ducting in one day using some 36 inch long zip ties and screw on bases that I made but they can be found online to fit that size zip tie..http://www.waytekwire.com/item/21243/Cable-Tie-Mounting-Base-White/. I used about 15 total and I screwed boards to wall to hold system up more permenantly. Also if you have enough ceiling height to allow a split on the wall instead of putting them all on the main trunk it will allow less turbulance as there is half as many drops on the main trunk. I have a clearvue installed behind the door and can post pictures if you are interested.

This might be cheaper than where you are. McMasterCarr ASTM 2729 Fittings (http://www.mcmaster.com/#underground-sewer-and-drain-pvc-thin-wall-pipe-fittings/=y206l1) According to those prices i have close to 1200 in my ductwork for 10 machines and a couple extra drops available.
15 Wyes @ 24.30 = 364.60
14 - 45's @ 12.33 = 172.62
3 - 90's @ 21.71 = 65.13
100' 6 in.@ 32.05 = 320.05
10 Gates @ 15.00 = 150.00
25' 4 in Hose = 45.00
10' 6 in Hose = 65.00

Matt
317365317366317367317368317369317370

[Rick Potter]

I got my 6 and 8" spiral metal ducting from a local AC supply store. It is the type that has ends like heater ducting (duh), and it really wasn't that expensive. It was six or so years ago, and if memory serves, it was cheaper than PVC.

[William C Rogers]

Southern California, Los Angeles Area.

I mispelled the name, it is Fergusons plumbing. They have a location in LA, and will have what you need.