J. Phil Thien's Projects

Thats correct.  His site is big but if you just go right to the build instructions you can see its really not hard.  Thin sheet metal like 24ga can be cut byhand.  Thats how i built my setup.  Sheet cost me $14 at a real metal supply.  Much cheaper than box stores!

You will also see that his full advice is a larger blower than you will have.  He comments that for the 3hp 13" impeller crowd it may be best to scale his cyclone to 20" dia as opposed to 18".  This will also increase height slightly.  He simply trys to reduce static pressure so the small blower can still move the CFM he think you need to move in the ducting.  Youll have to see how it feels to you...but the cyclone is way too easy not to try it.  Its rare to find something so well designed and easy to build... And free.

Here are a couple pics of what I built.  The baffle detail cant be seen but I did use about a 3" slot.  The blower inlet is 9" diameter and extends to within about 3" of the baffle.  Given the dims of everything, it means the slot to "blower pipe" is about 2.5" on the horizontal plane.

The separator inlet is 5"x7" and has a "straightener" down the middle (making 2 effective 2.5"x7" inlets)-have no clue if it helps or hurts.  The inlet total area is roughly a 7" round equivalent.  I did watch it pull in some dust as I held a can in front of the inlet...it may favor taking the dust in on the inside half of the inlet which would be the smallest effective inside radius. 

Basically need to put a view window in this thing and see whats going on.  Im sure there are improvements to be made by tuning the slot position and working with the blower inlet pipe distance to baffle.  The bell end and straightener in the blower inlet appeal to me as experiments.  Also thinking to use some items from the grocery store to see if I can get any objective idea about separation that would be easily duplicated by others.  I tried sugar which it captures easily and flour which it doesnt.  Maybe look at some other things like hot chocolate mix etc.

But the bottom line is that I dont think you can get to the really fine stuff with this sort of a setup.  Ultimately small particles are still able to follow airflow in these sort of separators and wont fall out.  Large particles experience sufficient centrifugal force even with relatively large diameter separators that they fall out.  I think thats why the sloping sides of the cyclone cone are so critical and why the truly great designs like Pentz work where other off the shelf "cyclones" dont.  For me, I want to make this as good as I can and learn something new (the Thien baffle is clever and you can learn alot about fluid flow tinkering with it)-but I exhaust outside so its really not too critical.  The hoods for my gear are way more important. 

Coalsmoke

I think I have done what you are now going to do.  I have a separator 20" diameter and 16" tall.  Ill post a pic at some point-not really pretty.  It is essentially like the top part of a cyclone with rectangle inlet and air ramp.  Instead of the cyclone cone at the bottom I put a baffle on it because I need something portable.  I roll the whole thing outside to use it-its life started as a 5HP Grizzly double bag unit.  I dont think you will achieve your objective of good fine separation with this sort of scheme.  As I said Ill post more later but for true fine separation I think you really have to go for the full cyclone.  And if you look at the Pentz plans, they arent really very hard to build and dont take up so much floor space.  It was simply too tall for me to wheel around or I would have built it.  When I post pics, Ill add details and perhaps others can give me ideas to try and improve the fine separation.  The user Retired2 seems to be on the ball and Id read his posts/Bill Pentz site before attempting a build to capture fines.

Retired

Do you consider anything from a table saw as "fine"?  For instance i ripped some white oak as a test and did see some pass thru.  However in the trashcan, i did capture alot and scooped up some and dropped it back into the can to get a feel for how much of the capture would tend to want to stay airborne.  On the drop there was significant material that would float for a while.  Not very scientific I know. 

By the way I like your work.

I have been reading the forum concerning the bell ends and air straightners.  Interesting work.  One post indicated that there may be more flo thru of fines with the bell end.   In addition to the current draw and CFM measurements, has anyone done anything to see what sort of fine separation these setups are capable of?  I recently built a setup that is essentially the top half of a cyclone (rectangle inlet and air ramp) but use the thien baffle where the cone would attach.  The blower is a 5hp grizzly with 13" impeller i got on craigs list. 9" inlet to the blower extending to within about 4" of the baffle.  The setup seems to work fairly well.  But i have no reference to judge separation quality.  Currently doesnt matter too much since im exhausting outside but id like to see how other systems work.  I know it gets table sugar quite well but whole wheat flour goes thru as I expected.  Im thinking to add the straightners but am sorta skeptical on the bell end if it hurts separation.