Sorry Phil,
I did not know... (below)
OK here is my post from Phil' site
For starters - I would like the thank Phil Thien for his baffle concept. His work on this idea is what made my version possible. (Thanks Phil!)
I should of taken more pictures when I created this version, but to be truthful, I was not sure it was going to work.
As many of you probably have done is read Bill Pentz dust collection site, and after I did, it really scared me. I have a very small basement shop and wanted to put in a cyclone but as you might be, I could not afford the expense nor did I have the ceiling height to install one. Woodworking is a hobby for me.
After seeing Phils design I wondered if this could be adapted to be used with 6" ducting instead of 4".
I have a Harbor Freight dust collector with a .5 micron Wynn Environmental filter. Worked great when clean but it plugged quickly and I did not like the material going through the impeller.
I came to the conclusion I needed a pre-separator and like most who have progressed with dust collection opted for a trash can separator.
Though they work, they killed the amount of air flow especially with 4" ducting. Well to make a long story short - below is a combination of both Phil's design and Bill Pentz cyclone.
Made rather inexpensively less than $50.00 for materials (not including the HF dust collector and 6" PVC ducting).
Made using a 5' -6" metal duct from HD, some threaded rod with wingnuts and a 2' x 4' piece of melamine.
Here is the first set pics: