Making a Cyclone from a Drum Dust Collector

[Julie Moriarty]

I have a DELTA drum type dust collector that I bought in the early to mid 90's. As soon as I hooked it up I hated the dust bag that hung on the side. It took up a lot of room when inflated, reduced the airflow and did a very poor job keeping the fine dust from re-entering the workshop. So I removed the bag and vented it to the outside using a standard dryer vent and some metallic flexible duct. I then used DWV PVC and routed that around the perimeter of the shop and installed branches with gate valves for all the tools. It has worked like a charm ever since.

Except for one LITTLE problem...

The airflow through the system was unencumbered by the dust bag and it blew through so fast almost all the dust blew directly outside. When "the-one-who-mows-the-lawn" complained about the piles of sawdust accumulating outside, I would go out there with a rake and make it "disappear". I was working then and didn't really do a whole lot of woodworking so the occasional piles weren't really a big issue, especially if I got out there and raked them away before the lawn got mowed. Then came retirement and the chips really started to fly. And that pile was becoming harder and harder to make disappear.

I remembered seeing an article in a magazine, I was thinking from the mid 90's, that showed how to make a cyclone dust collector out of a drum dust collector. I rummaged through my collection of old magazines and found the 1997 WOOD Magazine that had the article, along with the (partially) full size cutting template perfectly intact. That came in very handy when making the inlet cuts on a 6" piece of duct as well as the cut on the main cylinder.




The instructions said to use 30ga roof flashing. It's pretty flimsy but I figured they must have tested it and found no problems. The 6" duct I had, that's been sitting in my garage for 15+ years, was pretty heavy duty and forming it so it didn't distort the roof flashing took some work. I sealed all the joints with duct seal and caulk.


I used a garbage can to hold the unit in place so I wouldn't crush the cone. The garbage can used to hold scrap wood - that's what's on the floor in the background.

I used biscuits in all the joints. Most of the material I had in stock and I ended up using MDF for the back, that's why I decided on biscuits and glue rather than screws like the instructions showed. I also made the sides shallower because I wanted access to the back in case I needed to get back there to screw the frame to the wall. I ended up making cleats for mounting. The metal piece on top in the above picture is the bottom of the fan/motor unit.


I painted the wood black and used blue painter's tape for the accent lines. The color of the tape was so close to DELTA blue and it was so easy to apply, I couldn't resist. I was going to dress it up with a "DELTA" logo on the cylinder but I figured I made it so why not use my woodworking logo and modify it a bit to go with the DELTA logo?

I used 6" duct to connect to the existing 4" DWV PVC and taped the joints with metallic fiber tape. Then I grounded the ducts to the collector.

When it came time to test it, I decided to vacuum out the dust from my shop vac. I use that a lot when sanding so I knew there would be a lot of fine dust in it. As soon as I turned it on the cylinder drum collapsed! Yes. The sheet metal was too thin! I took a band of heavier metal and riveted it around the circumference. That seemed to hold but I can still see a small section pull in right next to the 6" inlet. Maybe I'll add another metal band there later.

As for what ended up outside, I'm happy to report almost nothing but some very fine dust. This thing really works! And it seems has better suction than before. But if you decide to make one for yourself, use heavier gauge sheet metal. I also found the template they provided for the three sections used to form the cone weren't quite right either. So when making the cone, make it longer than you need and trim it to fit.

All in all I spent about $70 for the flashing, (1) 6"T, (2) 6" to 4" reducers, (2) 4"x36" duct, (1) 4" elbow and (2) 6" bands. I had the wood, 6" duct, flex and elbows, metallic tape, rivets and duct seal.

On the downside, I'll have to empty this thing now!

[J.R. Rutter]

So much win in this post. Nice job!

[Stephen Cherry]

two thumbs up.

[Steve Peterson]

That is way cool. The logo is a nice touch.

Steve

[Bruce Wrenn]

Having built about fifty of these in workshops, I learned a couple of things. First, you can get both cylinder and cone from one 3' X 8' of 26 gauge sheet metal. Second, you can cut cone in one piece. To make layout easier, I made a story stick with radius on it for all cuts on cone. Thirdly, Home Depot, among others sells a MACO a tool that cuts the notches for the tabs. I have exactly same blower on mine, but made a doughnut to go between top of cyclone and bottom of blower assembly. Instead of venting outside, it goes to a pentuim under the waste can which has seven 6" X 65" filter socks. I even have a sensor in panel box that controls unit. No searching for remote. Wood online used to have a forum devoted to DC including these units.

[Julie Moriarty]

I would have loved making the cone out of one piece - less air leak and such. The instructions from WOOD said to use double sided tape at the joints and rivet them for both the cone pieces and the cylinder. I have a MACO edge bender that's 24" long and bends 3/8" and 1", if you go to the max depths for each side. I used the 1" edge and bent over all the joints. Then I took a steel roller and smashed the joints tight. You have to remember, this is VERY thin roof flashing and it doesn't take much to compress it.

When I sucked up the waste from the shop vac I heard a lot of little pieces rolling around. It made me wonder if there would ever come a time when one would blow right through.

I'm totally convinced about the effectiveness of a cyclone dust collector. Mine vents outside and even after sucking up over three inches of very compacted dust, the type that sticks to your ribs, almost all of it ended up in the drum. When I looked outside, I couldn't see any evidence or any wood chips. All I saw was a fine dust, which unfortunately attached itself to the side of the house. But we'll worry about that "when the time comes"

[steve joly]

Nice work, that same dust collector was one of my first tool purchases, and my intentions were to build it into something exactly like what you have there. Unfortunately plans changed and the machine is in storage for a couple years while I build a house, however once the house is done I have this thread saved because I will be referencing it as I put my DC system together.

[Julie Moriarty]

This past week I have given the CDC a solid test. To date it has had to deal with dust from:

• Over 200' ripping 5/4 cedar
• Over 700' 3/8" cedar roundover
• Over 30' 1/2" cedar roundover
• About 10' bandsaw cuts in 4x4 cedar
• Numerous crosscuts on the miter saw
• Cleaning out the dust bag from the belt sander, at least 1/2 dozen times
• And a whole bunch of other stuff

The good:

• On the router table where I split off a 4" into a 2" for the top and 4" for the bottom, it picked up EVERYTHING. That's a first. I usually have to deal with dust left somewhere and it often gets clogged on the 2" end even though I have blast gates controlling the 2" & 4" airflow.
• On the mitersaw, it seemed to almost completely eliminate any airborne dust.
• On the tablesaw there was still sawdust coming out the front and rear but I won't really know how effective it is until I close those areas up.
• On the bandsaw it seemed to pick up pretty much everything and kept the internal compartment free of dust.
• I could have (2) 4" blast gates open at the same time and still get decent suction from both.
• The dust in the drum is building up rapidly and nothing but very fine dust is getting outside.

The bad (and the ugly):

• The couple of times I started it up with all the gates closed, I instantly knew because I could hear the sheet metal collapse. The 30ga roof flashing for the main cylinder is definitely too thin.

Overall it's like I bought a more powerful duct collector. I never expected that. Even though the intake and exhaust ports for the factory DC are 4", I'll bet you can run 6" with this new setup. I'd rate this upgrade a 10, as long as you use a heavier grade sheet metal for the cylinder.

[Art Mulder]

The bad (and the ugly):

• The couple of times I started it up with all the gates closed, I instantly knew because I could hear the sheet metal collapse. The 30ga roof flashing for the main cylinder is definitely too thin.

Julie,
Couple years ago I read a story of a guy who built his own cyclone, and was worried about pipes collapsing. He built a "safety valve" at the end of the ducting -- he added a flap that was held closed with a strong spring. Then if he forgot to open a gate, this flap would suck open, which prevented any pipes from collapsing.

You might try something like that,

...art

[Michael W. Clark]

The bad (and the ugly):

• The couple of times I started it up with all the gates closed, I instantly knew because I could hear the sheet metal collapse. The 30ga roof flashing for the main cylinder is definitely too thin.

Good point from Art. I've also used a counter-weighted butterfly damper for this. It's the same as a regular damper except you attach a threaded rod to the shaft. Put weights on the threaded rod and you can move them to match the max SP you want. Or, just always keep at least on gate open.

Mike

[Mark Burnette]

I wonder what your actual CFM is at the DC with your small-ish pipes, many bends, and flex hose? I also use DWV pipe with 4" main line & 3" drops and "by the book" it's undersized--although I don't have any performance problems. Several years ago I tested the flow rate of my DC right at the 4" inlet. My 25+yo Cincinnati Fan 2-stage DC is rated at 1300CFM and I measured an actual 650 with bag removed, 450 with bag on (I use a 5 micron knit polyester bag that's larger and finer than stock). This was with all gates open. The flow dropped to about 200CFM with only one gate open at my farthest tool. These aren't exciting numbers but I don't have any problems with clogs, dust accumulation in the pipes, or dust not staying in the drum. Also even though my bag is far from today's state-of-the-art, I'm happy with it and I don't get any fine dust build-up in the small closet my DC is in.

My assumption is with low velocities you might not get enough swirl in the drum for the dust to hurl against the drum side and fall to the bottom. Sounds like your dust was "short-circuiting" from the lid inlet and right up the impeller with too little dropping out in the drum. My unscientific opinion is your cyclone is doing a better job with your low-ish velocities than a simple drum ever could.

[ian maybury]

Hi Julie. Good going. DIY cyclones are hard work, aren't they? Tough on the hands too. I'm drawing from your post the possibility that you might go back into your cyclone again to do some tuning, so here's some possibilities to play with based on what i found.

It's possible to use a local HVAC fab place to roll the main cone and cylinder and roll seam the two together for very small money (think i paid about €150) before building the rest yourself. I got them to CNC laser cut the ring that's formed into the ramp as well, and to form the round to square transition on the inlet chute too. These guys are set up to spit this sort of work out unbelievably quickly, and the material costs very little.

The big advantage is that you get accurately formed parts, a nice neat and truly circular joint in the cyclone body that also functions as a reinforcing rib, and can use a heavier gauge of sheet metal. (i had a go at rolling around on the floor of my shop wrestling with trying to manually form what was probably some 18G material around a pattern before switching to plan B)

Single stage cyclones like we use are right on the limit of their capability where fine wood dust is concerned. It's not something i've seen tested, but it might be worth considering a neutral vane inlet (the downwards angled inlet and spiral ramp in Bill Pentz's highly regarded cyclone here: http://billpentz.com/woodworking/cyc...ycloneplan.cfm) - it avoids the incoming airflow messing up the pattern of the rotating air flow inside the cyclone. The proportions, diameter, length of cone, size of outlet etc reputedly all make a difference on fine dust too, as does allowing a goodly length of straight duct run into the inlet.

Bill based his design on a model that's long been proven in industry for fine dust applications. His page shows how to adjust the dimensions for different CFM/airflow.

ian

assembled cyclone.jpg

[Lornie McCullough]

Great job..... beautiful cyclone!!

Lornie

[Julie Moriarty]

The only collapsing I've experienced are from the main cylinder in the cyclone. The pipes are fine. When I riveted the metal band to the exterior of the cylinder it stopped most of the collapsing. Knowing me, I'll wait until I run across thicker sheet metal (Home Depot doesn't carry it) or I decide to actually make an effort to run out to a sheet metal fabricator and pick up something there.

I did think about having a fabricator make up the sheet metal part of it but then what fun would that be?

Before I made the cyclone, dust would blow so fast through the system it would blow chips out 15' and farther from the side of the house. I had a standard dryer vent installed but it was the type with several louvers, not the hooded type with a single flap (which is what is now installed). Those louvers would open up parallel with the ground and, from what my kids reported, chips and dust would fly!

I was out in the yard working on some landscaping. We have lilies planted right where the vent is. In the summer they would get big enough to catch the chips. I finally raked it out the other day. It was probably 4-6" deep. And farther out, the grass has grown over it and it's spongy there.

FWIW - the DWV pipe I used to run through the shop is just pressed together. I didn't glue it because I keep thinking I'll sell the house "next year" and I want to be able to relocate it to "the next shop". So there is probably a lot of air loss at the couplings and fittings and also at the blast gates. I don't know what the CFM is at any point in the system but I do know dust collection is a lot better now and there's no sign of any chips making it outside.

[Mark Shirley]

Julie,

May I ask what issue of Wood that is in? I have a drum collector as well I'd like to give this treatment to.