Shop Built - Thien Cyclone Separator Lid. Dust Collection pre separator. (Rating: 5)

I have been getting a few questions about the Thien Cyclones I have been building, and figured I would write a quick review of them, and try to answer the questions I see about them..

For starters a Thien Cyclone Separator is NOT a true cyclone, but does operate in a psuedo cycloninc fashion. Meaning the incoming air stream spins around the outside of the vessel / dust bin and drops its load of dust, and larger particles in much the same way as nearly all the other separator lids do. The BIG difference in the Thien is the baffle. The baffle consists of a disk that is sized to the inside diameter of your vessel, with a 240 degree slot cut out of the outside edge to allow dust / debris to drop out of the air stream, the baffle physically interferes with dust, and debris from trying to get back into the air stream going out of the cylinder and up into the DC and in turn the filter.

The Thien Cyclone Separator is a do it yourself affair. This is NOT something that is commercially available, although I bet Phil (the inventor) could probably make a pretty penny off of these if he manufactured them and sold them).

Phil Thien, the inventor of the baffle / lid maintains a web site complete with discussion forum to give people instructions and advice on building their own Thien Cyclone Separator lid, and Thien Baffle.

I actually got to looking into the Thien setup after reading well into Bill Pentz's materials on dust collection. I am working within a budget, and needed the best bang for my buck. While Bill recommends a Neutral Vane in the inlet ring of the DC to keep the filter clean and your CFM constant. After talking the issue over with several users that have experimented with both, I am convinced that a Neutral Vane, while helpful in putting, and keeping the air stream moving in a cyclonic motion, does NOTHING to prevent scrubbing, and thus, is performs at a far lower level than the Thien system.

Keeping budget constraints in mind, I tried following Bill's advice as best I could, but there were some big areas of deviation, that I simply at this point accept out of lack funds to do otherwise. This has little / nothing to do with the Thien system except for how I built mine as the Thien setup can be scaled up, or down as need be.

On to the questions I keep getting…

#1. Why 4" ducting instead of 6"? Simple. Money, and my tools. All of my tools are fitted with either 4", or 2.5" fittings. There are a HUGE number of problems associated with using 6" in this regard, and I am in no way ready to scale up my dust hoods yet. I would have to either majorly modify, or replace 90% of my equipment, and I am NOT ready to do that.

#2. Why a 55 gallon barrel instead of a galvanized trash can? My Shop Vac setup is based on a 20 gallon galvanized trash can. Simply put, it fills up too fast, and the sides tend to want to buckle if the dust port gets plugged by say dropping the hose of the floor… A 55 gallon barrel allows for less frequent emptying of the vessel, as well as a much sturdier vessel resisting buckling. Combine this with the fact that the drum has a buckle / gasket arrangment for an air tight seal, and using the drum and modifying the original lid made perfect sense to me!

#3. Why did you use hardboard for the baffle when the instructions show plywood or MDF? Weight. I based my lid off of the relatively soft plastic top of the barrel, and wanted as little weight on the lid as possible. hardboard is inexpensive, lightweight, and quite durable. It was a logical choice for my application.

#4. Why use threaded rod instead of dowels for spacers? Ease of use, smaller footprint presented to the airstream. Most of the dowels I have seen in use on these is 1/2" at a minimum. I use 1/4" all thread with fender washers / double nuts. My setup presents less obstruction to the airstream.

#5. What would you have liked to have done differently? Used a side inlet instead of the top. I would like to reduce the two bends it requires to get the air stream moving where we want it to. This may be coming in a future rework of this device.

#6. What else have you done, or are you doing with your dust collection system to improve efficiency? The biggest thing I did was to immediately take the 5 micron bag OFF of my HF DC, and replace it with a Wynn 35A spun bond poly filter. I know the paper blend filters down lower, but the spun bond can be washed and re-used, and it is at the filtration level I want. I have a strip of foam weatherstripping that is in the notch where the band gizmo for holding the lower bag on is. It seals the bag and keeps dust from blowing out of the place where the plastic bag meets the inlet ring. I am researching options to improve air flow between the impeller and inlet ring. There is a Stovepipe mod, where folks are taking those bendable stove pipe elbows and short pieces of 5" stove pipe to replace the ribbed flex hose in this area that is reported to work exceptionally well. My blast gates are self cleaning models that appear to seal quite well, and I am working to reduce / eliminate any and all tight turns / elbows. Including the flex line from the Thien Cyclone to the DC.

#7. Are you going to upgrade from 4" to 6"? I don't really know. The 4" duct at least APPEARS to be working well for me. I see no hanging dust in the air after I have been working. I think it would take me seeing test results with an air quality meter to convince me 6" is really neccesary. Of course YMMV.

#8. How well does the Thien separator work? Actual numbers of fine particles getting to the filter is next to impossible for me to tell. What I CAN tell you, is that I have filled the drum up with shavings, sanding dust, etc… from lots of heavy use, and have had less than 1/4 cup of fine powder that I can knock down from the filter. Speaking of, In order to keep what little dust is there from building up too much on the filter, after the end of every work session when I power down the DC, I tap down the cartridge across the top, and all the way around the filter. This method is working for me very well so far…

I hope this has been helpful, and answers folks questions about this device. If you are running a single stage DC, I highly recommend this addition. It is time, effort, and money well spent!