Mark Burnette
01-30-2013, 11:12 AM
I have a 2HP Cincinnati Fan DC that has a home-made shroud mounted around the impeller intake. This shroud limits my drum capacity so I was wondering what would happen if I replaced it with a Thien or "wok" baffle or simply removed it entirely.
http://i170.photobucket.com/albums/u273/guy48065/Shop/DCshroud.jpg
Unlike most the experiences I've read here I've never felt I have a problem with too much dust getting into the bag--except when I forget to check the drum and the level gets up to the shroud. First I needed to test how much dust was getting past the swirling vortex in the drum, past the shroud and into the bag. To do this I took about 1/3 drum of varied sawdust (planer & jointer shavings, TS dust, sanding dust, floor sweepings...pine/oak/plywood/PT/MDF were all in there). I sifted the dust through a 1/4" soil sifter to remove any chunks, then weighed the empty drum.
http://i170.photobucket.com/albums/u273/guy48065/Shop/0129131814.jpg
I would then suck up the dust and weigh the bag & drum, then empty both into a clean trash can and re-weigh everything to make sure the numbers added up consistently. I did this 3 times as I refined my technique and in all cases the numbers repeated within .1 pound out of 28 pounds of dust (the scale is a calibrated 200 lb unit with .05 lb resolution). I then repeated the test with the shroud removed.
Results: With shroud in place I would get 1.1 lbs of fine wood "flour" in the bag out of 28 lbs total, or 4%. With no shroud I got 1.4 lbs or 5%.
I put a 4 foot fluorescent fixture behind my drum while I was sucking up the dust and could see the swirl through the translucent drum. I couldn't tell any difference in the vortex speed or pattern with/without the shroud. At this point I don't know if I will gain anything by making a different baffle but I will gain lots of drum capacity if I run with no baffle.
I'd love to hear from others who have baffled their 2-stage DC (not a "trash can separator"--that's been well covered). This DC seems to perform much better than other 2-stage units I've read about (and that's not very many--for whatever reason this type was never very popular). I've run this system unchanged for almost 20 years in my current house, and for several more in a basement shop before that. It's not "ideal" but it does the job.
http://i170.photobucket.com/albums/u273/guy48065/Shop/DCshroud.jpg
Unlike most the experiences I've read here I've never felt I have a problem with too much dust getting into the bag--except when I forget to check the drum and the level gets up to the shroud. First I needed to test how much dust was getting past the swirling vortex in the drum, past the shroud and into the bag. To do this I took about 1/3 drum of varied sawdust (planer & jointer shavings, TS dust, sanding dust, floor sweepings...pine/oak/plywood/PT/MDF were all in there). I sifted the dust through a 1/4" soil sifter to remove any chunks, then weighed the empty drum.
http://i170.photobucket.com/albums/u273/guy48065/Shop/0129131814.jpg
I would then suck up the dust and weigh the bag & drum, then empty both into a clean trash can and re-weigh everything to make sure the numbers added up consistently. I did this 3 times as I refined my technique and in all cases the numbers repeated within .1 pound out of 28 pounds of dust (the scale is a calibrated 200 lb unit with .05 lb resolution). I then repeated the test with the shroud removed.
Results: With shroud in place I would get 1.1 lbs of fine wood "flour" in the bag out of 28 lbs total, or 4%. With no shroud I got 1.4 lbs or 5%.
I put a 4 foot fluorescent fixture behind my drum while I was sucking up the dust and could see the swirl through the translucent drum. I couldn't tell any difference in the vortex speed or pattern with/without the shroud. At this point I don't know if I will gain anything by making a different baffle but I will gain lots of drum capacity if I run with no baffle.
I'd love to hear from others who have baffled their 2-stage DC (not a "trash can separator"--that's been well covered). This DC seems to perform much better than other 2-stage units I've read about (and that's not very many--for whatever reason this type was never very popular). I've run this system unchanged for almost 20 years in my current house, and for several more in a basement shop before that. It's not "ideal" but it does the job.