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

[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):

1. 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.
2. 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.
3. 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.
shop image.png

[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.