If I don’t have a filter, is there any reason to have a cyclone?

[David Croteau]

I haven’t found a discussion of this particular dust collection question and would appreciate feedback.

From what I understand, a cyclone separator’s primary function is to reduce the volume of material that ends up in your filter. So if I don’t have a filter, is there any reason to have a cyclone?

Context:
I’ve got an old 1.5 HP Delta 50-760 (with 4” S&D pipe) with contractor saw, benchtop planer, jointer, router table, miter saw. Far from an ideal set up but I’ve only spent limited time the workshop on a project-by-project basis (kitchen cabs, built-ins, some furniture, etc.). Now, though, I’m anticipating more time in the shop during semi-retirement and would like to improve my dust collection a bit, without spending a fortune.

After reading DC threads here, I thought about:


Adding a cyclone separator, probably a Super Dust Deputy
Replacing the filter bag with a pleated filter, probably from Wynn.


However, it occurred to me that my set-up would allow for venting small stuff out a window (no immediate neighbors, hidden from view, moderate weather, etc.) and therefore may not need a filter at all. So now I’m thinking about plugging the filter bag opening in my Delta with a plywood disc that has a coupling for a hose to go to a window vent (similar to a dryer vent). This led to my question: if I don’t have a filter, is there any advantage in having a cyclone?

Related:

If I close off the filter opening, accessing my Delta's plastic bag system for chips would be difficult, so I'd probably need to replace with a “skirt” and can system.
If I don't spend all that money on a pleated filter and cyclone, I may spring to upgrade to some 5" metal duct; maybe better bang for my buck there.

[Marc Fenneuff]

However, it occurred to me that my set-up would allow for venting small stuff out a window (no immediate neighbors, hidden from view, moderate weather, etc.) and therefore may not need a filter at all. So now I’m thinking about plugging the filter bag opening in my Delta with a plywood disc that has a coupling for a hose to go to a window vent (similar to a dryer vent).

This is valid based on your stated situation.


... if I don’t have a filter, is there any advantage in having a cyclone?

A properly-sized/plumbed system with a cyclone is going to remove most dust, shavings, chips etc. In your situation I would keep the cyclone to dispose of the waste rather than pumping that stuff into the outside air.

In a small shop with fixed ductwork, the minimum is kinda 2HP. If you are rolling the Delta / SDD around to one tool at a time, you should be fine with 1.5HP /4".

[Jim Becker]

Advantage to a cyclone, even if venting air outside, is that the debis all ends up in a bin without passing through the impeller and in a very controlled fashion. That also means you can take advantage of things like floor sweeps for general cleanup without risking metal sparking on impeller blades. But you can certainly use a simple blower to move material outside to an open bin or even a pile if you choose. I personally would never go back from having a cyclone...something I adopted in 2000 and upgraded a few years later to a larger unit.

[Marc Fenneuff]

Advantage to a cyclone, even if venting air outside, is that the debis all ends up in a bin without passing through the impeller and in a very controlled fashion.

Completely forgot about this! When small (<1") cut-offs make it back to my metal cyclone they make quite a racket. Would not want that regularly going through the impeller.

[David Croteau]

Advantage to a cyclone, even if venting air outside, is that the debis all ends up in a bin without passing through the impeller and in a very controlled fashion..

Ah, that makes sense. I hadn't thought about that advantage. Thanks.

[glenn bradley]

Advantage to a cyclone, even if venting air outside, is that the debis all ends up in a bin without passing through the impeller and in a very controlled fashion.


Ah, that makes sense. I hadn't thought about that advantage. Thanks.

Ding, ding, ding. Flowing spoil can be quite abrasive. Just take a look inside one of your pipes; mine are scoured squeaky clean. Not a deal breaker. Single stage units push spoil through the impeller all the time so the choice is yours.

If I could do without a cyclone, I would. A separator puts a tremendous hit on your air flow. If I could just let it fly, I would be sorely tempted ;-) My current plans are for a cyclone with the post separator airflow blowing outside. My neighbors aren't quite far enough away for me to pump gallons of spoil into the wild several times a week . . . I'd scare the livestock.

[David Croteau]

A separator puts a tremendous hit on your air flow.

Yeah, I saw numerous posts mentioning this and it had me concerned, especially with a little 1.5 HP collector. (It's one reason I'd been thinking of jumping up to 5" ducts.) I'm hoping maybe some of this loss can be offset by the easier air flow of a no-filter set-up and by tightening up my duct connections. I guess we'll see.

[Matthew Hills]

The venting a cyclone out a window seems to work reasonably, as only very fine dust remains.
I don't think sending all debris out the window is viable if you are generating regular sawdust, planer shavings, etc.

To save cost, You might be able to run a thien separator with a 3hp+ blower and get enough separation to vent outside the window.
Or look for a used cyclone in your area.

Matt

[Bruce Wrenn]

Add a Thien baffle inide your current DC. Separation is greatly improved, without changing foot print

[Doug Garson]

Don't know your level of knowledge of fluid mechanics and I know it's been decades since I did any design calculations so I'm not sure how well I can explain this but here goes. Don't just replace the outlet filter with a plywood disc with a 4" hole and flex hose to the outside. You will get much less pressure drop and thus more flow if you can fabricate a gradual transition like a cone from the 20" or so diameter of the filter down to the 4" or so diameter of the outlet hose or duct. The bigger your outlet duct and the more gradual the transition the less back pressure on your dust collector fan and the more flow you will get.

[Bill Dufour]

It kind of limits your shop time to only good weather. You can not heat or cool a shop with a dc discharging all the conditioned air at several hundered cubic feet per minute.
Bill D

[Curt Harms]

Add a Thien baffle inide your current DC. Separation is greatly improved, without changing foot print

That's what I have. A small amount of sanding dust type fines do make it into the filter but no chips or anything large.

[Ron Selzer]

IMHO you don't have enough fan to utilize a cyclone, way too much air flow lost in a cyclone.
Make a cone for the top with at least a 6", 8" would be better to exhaust out side
this will allow the best probable airflow you can get now, later when you upsize to a 5hp or bigger blower then consider a cyclone.
Good luck
Ron

[Jim Dwight]

I use a "2hp" HF motor and blower mounted to the wall of my little shop, in the corner, sitting on top of a Super Dust Deputy. There is a home made plywood dust box under the cyclone and the air goes outside. I have 5 inch snap lock metal piping. There has never been noticable dust on the bushes closest to the DC exhaust. I sometimes use a little space heater in the shop in the winter but in SC where I am, the main thing is cooling. So far that is just a fan. I might go to a window unit for the hottest days. If I need to, I will add a filter. I have not measured airborne dust with my setup but in terms of getting the big chips out of the table saw, bandsaw, router table, planer, jointer, or CMS it works well. Leaving the doors open is part of my dust "solution". I will probably have to do something different to be able to leave the shop closed up. Simplest would be to add a fine furnace filter to the box fan I already have.

[John K Jordan]

I just saw this and don't know if it was mentioned, but a good long-cone cyclone like the ClearVue will remove almost everything from big chips down to extremely fine sawdust. I use a 5hp ClearVue. I have good filters and return the filtered air to the shop but the separator is so efficient almost nothing even makes it to the filters. If venting outside, there would be very little sawdust in the exhaust stream.

The short cone cyclones are not as efficient in the separation.

JKJ

[glenn bradley]

I'm hoping maybe some of this loss can be offset by the easier air flow of a no-filter set-up and by tightening up my duct connections. I guess we'll see.

I'm hoping the same thing for my new shop build. I am over doubling my space and still have just a 2HP cyclone. I should really bump up to a 5HP but, there is only so much money and we have to make choices. Like you I am hoping a streamlined and well sealed duct system along with me exhausting, post-cyclone, into a folded pathway (to kill noise) that leads outdoors will do the trick. I have designed it in such a way that if need be, swapping DC's can be done pretty painlessly except for the wallet impact.

[Tom Bender]

A cyclone should be sized for the system. It's not a 'one size fits all' thing. As cyclone efficiency goes up it is effective on finer particles. But it also eats more power (restricts flow). And for a given size cyclone there is an optimal flow so you need a bigger unit for a higher flow or it's not going to capture midsized particles in addition to restricting flow.

That said, an oversized cyclone will catch smaller particles with low restriction. So that is my suggestion here. It will still reduce flow a little and may not be optimal for fine dust but it will be a good compromise for your case. And if you go back to using the filter it will be ok.

[Michael W. Clark]

That said, an oversized cyclone will catch smaller particles with low restriction.

Hi Tom, please correct me if I misunderstand, but if the cyclone is oversized (designed for a higher flow), it’s efficiency will be reduced when operating at too low of low.

[David Croteau]

Just to check back in and say I’ve been following the responses here. Thanks for the ideas and insights.

I appreciate that if I were putting together a top-notch system for regular use (or just had $$$ lying around to spend!) the investment in a 3-5HP cyclone, larger ducting, etc. would make sense. I get it. That’s not going to happen, though, so I’m just trying to figure out what makes the most sense given my circumstances.

FWIW, here are more details.


SHOP & TOOLS: I’m an occasional weekend DIY’er, with 120V wiring in a detached 20x28 building that also serves as multi-purpose storage, garden shed, etc. The simplified sketch of my shop area and tools below is to scale. I usually sand outside, if at all possible, have a homemade fan/air filter to help capture some smaller dust if I have to sand indoors, and regularly use a respirator. I’m in a mild climate so windows and doors with good cross-ventilation are open much of the time and heating/cooling are not a major concern.
DC: My little 1 ½ HP Delta 50-760 DC has chugged along without problems for years. I don’t use a floor sweep and haven’t sucked up any metal, so the impeller is likely in very good shape.
DUCTS: I currently use the DC’s 5”-to-4” splitter to run two legs of 4” S&D PVC with gates (shown in pink, roughly). One ~11’ run goes on the floor straight to the planer and TS (with wye/gate to the planer, wye to accommodate collection at the TS blade). The other leg runs in an “L” about 24’ total past the jointer, router, and miter saw, with wyes and gates to each. (A straight-shot diagonal would be more efficient but would require overhead installation, which my limited-capacity DC and cathedral ceiling wouldn’t easily accommodate.) I’m open to moving things if there’s a clear advantage but this set up has served me pretty well.


Changes I’m considering (or not):


VENTING outdoors is the first thing I want to try. I’ll likely replace the bag with a plywood disk with large bell mouth/reducer (looking for a source now) to a 6” or 8” vent in a panel installed in that window. This should reduce the release of fine dust in the shop and increase air flow, compared to the old bag filter.
CYCLONE. The question of adding a cyclone—which prompted this whole thread—comes next. Since I’ve not had issues damaging the impeller after years of use, and don’t need to worry about clogging a filter, I’m not convinced adding a cyclone is worth the hit to my already limited air flow, not to mention the hassle of having to raise the motor to accommodate it and figure out a new barrel collection system. I’m not ruling it out but I’d like to try #1 first and see how that goes. Does the old plastic bag system for chips still work okay when venting outside? We’ll see, I guess.
DUCTS. Moving up to 5” duct would require a total conversion to metal, something I’m not eager to do, largely because of durability issues when low in the shop instead of hung overhead. Moving to 6” pvc duct probably outstrips the capacity of this little 1 ½ HP DC (does it?), though I am considering experimenting with it on the shorter run to see how it goes with minimal investment.


Does all of this sound like I’m ambivalent? Well, maybe. ;)
444887

[David L Morse]

...
DUCTS: I currently use the DC’s 5”-to-4” splitter to run two legs of 4” S&D PVC with gates (shown in pink, roughly). One ~11’ run goes on the floor straight to the planer and TS (with wye/gate to the planer, wye to accommodate collection at the TS blade). The other leg runs in an “L” about 24’ total past the jointer, router, and miter saw, with wyes and gates to each....

Changes I’m considering (or not):

Ventingoutdoors is the first thing I want to try. I’ll likely replace the bag with a plywood disk with large bell mouth/reducer (looking for a source now) to a 6” or 8” vent in a panel installed in that window. This should reduce the release of fine dust in the shop and increase air flow, compared to the old bag filter.

Does the old plastic bag system for chips still work okay when venting outside? We’ll see, I guess.



Venting outside will likely result in cleaner air inside the shop. I don't think you will see much, if any, increase in airflow unless your filter bag is really plugged up. With six inch duct on the outlet you might actually see a slight increase in loss compared to a new, clean filter. If you haven't cleaned you bag in years then that's another story, but your limitation is really the 4 inch duct.

Your existing centrifugal separator ("bag holder") should still put most of the chips in the bag.

[Peter Kelly]

My former MIL had no filter at all, didn't seem to stop her.

[Dave Sabo]

Add a Thien baffle inide your current DC. Separation is greatly improved, without changing foot print


or your wallet as much as a SDD.

I’d suggest the baffle too, given your collector and situation.

re: 6” pipe - don’t think your gonna like the performance. Your blower is sized for a max 5” pipe. Sure, it’ll move air through 6”; just not fast enough to be as effective as 5” or smaller.

[Brian Behrens]

I have a 5hp clearvue cyclone vented through the wall of my shop. Here in the mountains of N Georgia I haven't found it to be an issue, even in the summer, but my shop is well insulated and air conditioned by a mini split. In a really cold or really hot area, it could be an issue on days when the dc is running for hours on end.

I can't answer your specific questions about your dc, but I am a firm believer that the dc is the most important tool in the shop, and I would recommend skimping on other tools to get a better dc from the start. You can upgrade your table saw later, for much less money than a lung transplant.

One caveat to venting outside is the insane amount of noise that it produces outside the shop. I live in the woods with no neighbors, but if you were in a tight neighborhood it could definitely be an issue. It sounds like a helicopter is idling in my backyard when the dc is running and can be heard a mile away (no exaggeration)

[John K Jordan]

....
One caveat to venting outside is the insane amount of noise that it produces outside the shop. I live in the woods with no neighbors, but if you were in a tight neighborhood it could definitely be an issue. It sounds like a helicopter is idling in my backyard when the dc is running and can be heard a mile away (no exaggeration)

Have you read about using some sound insulation on the exhaust duct? When researching this before I bought my ClearVue there was discussion of this on the ClearVue forum. Some were using insulated HVAC flex duct. All mine is in a closet so I haven't experimented with this.

[Brian Behrens]

Have you read about using some sound insulation on the exhaust duct? When researching this before I bought my ClearVue there was discussion of this on the ClearVue forum. Some were using insulated HVAC flex duct. All mine is in a closet so I haven't experimented with this.

Thanks John. I do have the exhaust running through an insulated 10" flex duct but it's only a 2' run before it exits the wall. I've seen some designs for external silencers, but the noise doesn't bother me while I'm in the shop. I don't think you could get away with this method in a normal neighborhood though

[Jim Becker]

You do not want to use the non-metallic HVAC flex on the outlet if it's going to carry any material other than super fine dust... ;)

[Alex Zeller]

A friend of mine who's on the cheap side but also very handy bought one of those metal carts that you tow behind a lawnmower. He modified it with 1/2" conduit so it looks like a covered wagon and then wrapped it with chicken wire so he could use it to suck up leaves. It worked ok but his mower deck didn't have the force to keep from plugging up. Since moving away to NC and now having a shop to work in he's modified the cart. Now it's for collecting dust and chips from his shop. He put some fabric over the chicken wire and just backs it up and connects it to the exhaust pipe on the outside of his shop. It doesn't capture all of the dust but enough so there's almost no mess on the ground. If I'm not mistaken he has a 2hp Harbor Freight DC. Seams to me that if you're thinking of just letting the chips fly out the window or go with a cyclone (but not want to spend the extra money) then this could be an inexpensive option. Plus there's very little effort needed compared to removing the barrel of a cyclone and emptying it.

[David Sochar]

It is pretty simple - The cyclone slows down the velocity of the dust, allowing the larger bits to drop down and out of the waste stream. The finer bits still in the stream exit the cyclone and go to a rigid or fabric filter.

The sequence can be: Exit the shop, Cyclone, then Fan, then Filter, then return to shop. This allows the large bits to drop down into the collector before they go thru the fan. This keeps the shavings big and fluffy. Or it can be: Exit the shop to the Fan, then to the Cyclone, then to the Filter.

If you vent your pipe to the outside, you may be drawing down your heating system (forced air). That is, since you are venting outside, that pressure may be greater than the exit pressure from you collector. This will make for a dangerous situation in that Co2 may be drawn down the system into the shop, killing the inhabitants. Adding a way to return air to the shop will prevent the danger. Or just having your collector inside the building will eliminate the Co2 problem.

I built a room on the side of my shop that is 4' x 4' x 10' The fan and cyclone are in the top of the room. There are two access doors outside - one high, and low. All the shavings drop out of the bottom of the collector there, and the fines go to be filtered. The fabric filters are in the shop so the pressure is equalized.