Trash can pre-dust collector puzzle

I have a Penn State DC2V2 dust collector and have used it for many years as a roll around unit hooking it up as needed. Then I got a pre-collector cyclone 4" top for a metal trash can which collected all my trash very well leaving only a little remaining in the bottom filter bag. I recently piped my small shop with 5" metal pipe and fittings and made a new top for the trash can with 5" passthrough fittings and elbow. Now however the trash is sucked through the can into the bottom filter bag leaving only a little residue in the can. View pictures of my set up here http://www.nami-savannah.org/woodworking.htm Any suggestions as to why this is not working with 5" pipe/hose but ran fine with 4"?
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It sounds like your original top was bought and that you made your own top for the 5" pipe. Assuming that is correct, you must not have the air flown properly to create the cyclone effect.

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As I look at your new "top" it appears that they are piped in straight down. The trash can collector is a form of a cyclone and works because the air is swirled around and the dust drops out. Then lower velocity air exits from the center.
I'd suggest that you move the 5" exit to the center of the new top and either angle the 5" entrance (now moved to towards the edge) or add an elbow so that the air enters tangentially to the trash can's side.
Let us know how that works out.
FWIW I have the same DC, 6" piping and use a trash can collector only on my planer, so I use a 4" inlet (angled and tangential) and a 4" outlet (centered). Works well.
Bob wrote:

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Bob wrote:

I'm guessing that it's one of two things:
1) The 5" lines will pass much more air, and it might be enough of a difference to scour the trash can clean.
2) Your homemade cyclone lid might not direct the air properly to drop out the debris. I suggest having the input come in at a shallow angle along the top of the lid, as close as possible to the edge. You may also want to have the output stick down a bit into the container.
Chris
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From Bill Pentz' website:
Unfortunately, trashcan separators do not scale up well. Typical hobbyist trashcan separators work well until you have a system that moves more than about 450 CFM. That means any dust collector over about 1.0 HP will have problems with a trashcan separator unless the airflow to that collector is strangled by using far too small 4" ducting that limits the airflow. Using a 1 HP blower with 5 or larger ducting increases the airflow and keeps the dust from separating. Too much airflow simply scours the trash can empty of all but large blocks. My 1.5 hp system with a trashcan separator worked fine until I upgraded to 6" ducting after realizing my 4" ducting was strangling dust collection airflow. After upgrading to 6" ducting the increased airflow left my trashcan scoured clean. We could build a much bigger trashcan separator that would work, but for the 800 CFM we need for good fine dust collection, we end up needing a 52 wide trashcan that sits ceiling high.
http://billpentz.com/woodworking/cyclone/Index.cfm
Read the whole thing.
-Leuf
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Bob wrote:

Try aiming the elbow towards the outside wall of the trashcan. You can try adjusting that angle. That may result in reducing the airflow back down to the previous 4". However, I expect would be closer to 4.8" should be enough.
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On mine, the middle (to DC) is a straight run and the outer one (from saw) is a 90 degree elbow which seems to work well... maybe you're not getting the "cyclone" action? Mac
https://home.comcast.net/~mac.davis https://home.comcast.net/~mac.davis/wood_stuff.htm
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Thanks for all the help. I cobbled up a new lid with a shallower angle and entended the exit pipe into the trashcan which produced a little improvement. However, it was so negligible that I would still have to empty the bottom DC filter bag plus the little trash remaining in the can. Bill Pentz explains the problem well. "From Bill Pentz' website: Unfortunately, trashcans do not scale up well. Using a 1 HP blower with 5" or larger ducting increases the airflow and keeps the dust from separating. Too much airflow simply scours the trash can empty of all but large blocks. " Given this info I think I will just use the bottom bag for now until I can make or purchase a real cyclonic dust collector. Anyway, it's sure great not having to roll and hook-up every time I want to use a different machine. Now if I could only have automatic gates.... how quickly I become spoiled. Thanks again for all the suggestions and interest.
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Bob,
FWIW, take a look at the following links:
http://www.woodcraft.com/articles.aspx?articleid@8
http://community-1.webtv.net/WoodworkerJoe/BuildADustCollector/index.html
These might give you some help in redesigning your separator lid. Let us know how it works out.
Hope this helps.
Peter.

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