Thien's Baffle and Trash Bags

[Randy Klein]

I haven't seen this mentioned anywhere, but for anyone who has built a pre-separator for a 2HP DC, based on Phil's baffle design, can you put a trash bag in the trash can or does it get "sucked" out when in operation? I'm starting to really lean this way but having to dump a barrel full of dust and shavings doesn't seem very fun. If it can all be collected in a trash bag, that would be ideal.

[Deb Malloy]

I believe I read on his site that trash bags would get sucked in. The suggestion was to use a piece of laminate in the can to hold the bag in place.

Here's the like to the discussion forum, it may have some different solutions.

http://www.cgallery.com/smf/index.php?board=1.0

[David Hostetler]

I have a plastic "bag opener" thing a ma bob for lawn & leaf bags I got at Home Depot a LONG time ago that I thought about using in mine, but I typically empty my barrel outside, with the wind blowing away from me. I still need to try it though... Without some way to force the bag to stay open, it would get sucked in...

[Dan West02]

I haven't seen this mentioned anywhere, but for anyone who has built a pre-separator for a 2HP DC, based on Phil's baffle design, can you put a trash bag in the trash can or does it get "sucked" out when in operation? I'm starting to really lean this way but having to dump a barrel full of dust and shavings doesn't seem very fun. If it can all be collected in a trash bag, that would be ideal.

I asked Phil that very question and he said that yes, you need to have some method to hold the bag to the sides of the container or it will get sucked up.

[Alan Schaffter]

How about attaching your baffle rig to the discharge side of the DC blower? Then you can use a trashcan liner since the can is now under positive pressure. And . . . if you discharge outside or don't have too much filter back pressure, you don't even need the trashcan, you can mount the bag to the lid.

It is called a "push-through" configuration and it works great, at least with a cyclone.

Oh, and if you are worried about stuff hitting the impeller with the separator now on the discharge side, isn't that the way all single stage DC's work as supplied by the manufacturer?

[Adam Strong]

Oh, and if you are worried about stuff hitting the impeller with the separator now on the discharge side, isn't that the way all single stage DC's work as supplied by the manufacturer?

Most people with a single stage DC usually look to build in a separator before the impeller to drop out the big stuff. There is a real danger of spark or impeller damage with single stage DCs.

[David Hostetler]

Most people with a single stage DC usually look to build in a separator before the impeller to drop out the big stuff. There is a real danger of spark or impeller damage with single stage DCs.

Not to mention the sound of something metal hitting your impeller can make you jump a mile high, even using earmuffs!

[Adam Strong]

Yeah... quite the shot gun blast. And if it happened to knock a blade out of balance the followed vibration is quite disturbing as well. Nothing like the "holy crap, what just happened" adrenaline rush.

[Alan Schaffter]

You guys probably ground your PVC ducting too.

So, you are telling me that all single stage dust collectors manufactured in the last, hmmm lets say 40 or 50 years (tens, maybe hundreds of thousands of units?) are really dangerous and will cause fires and mayhem, because they don't have a pre-separator!!! Gee, I must have missed all the reports of same. Now, you don't want to do that with a machine that doesn't have a good steel or hefty cast aluminum impeller.

There is a VERY remote danger of a spark, but due to the volume and velocity of the air it is not a problem, any spark generated is quickly extinguished. I have been running two different push-through cyclones for nearly 10 years with the same blower/metal impeller and it hasn't happened yet! And believe me, I have sucked up lots of metal (steel cutoffs, shavings, nuts, bolts, chuck keys, tape measures, etc. ) and wood, and never had a fire, not even smoldering, etc.

My original highly modified Wood Mag cyclone built in 2001. I added a neutral vane and one of the first spiral inlet ramps, etc. and connected it in a push through configuration.



My current push-through cyclone is a Pentz 3D design I built in 2004.

[Adam Strong]

I've read your pervious posts stating the same thing in other threads... The danger of spark may be remote, but still possible. My main concern is damaging the impeller. I have had this happen before and it is no fun to fix or replace. I am glad your set up works so well for you, but there is no reason to sarcastically shut down what has been proven to be good advice. This same good advice can be found in many forums posted by many different people.

[Alan Schaffter]

I've read your previous posts stating the same thing in other threads... The danger of spark may be remote, but still possible. My main concern is damaging the impeller. I have had this happen before and it is no fun to fix or replace. I am glad your set up works so well for you, but there is no reason to sarcastically shut down what has been proven to be good advice. This same good advice can be found in many forums posted by many different people.

You are missing the point, my first point- Delta, Grizzly, etc. have been selling single stage dust collectors which have been safely used for 40 - 50 years (or more?) without pre-separators. What has changed all of the sudden that makes them dangerous ???? If they were dangerous to use without pre-separators the CPSC or other governmental outfit would have banned them in a heartbeat long ago!

Most of them have some sort of grid that will stop huge chunks of wood, but will not stop nuts, bolts and smaller chunks of wood from hitting the impeller. To cover themselves, Grizzly's manual says don't pick up metal. Fine, these are dust collectors anyway and for a number of other reasons you should clean your floors with a shopvac that has good static pressure, anyway. And, if somebody spends their hard earned money on a DC with a plastic or other poorly-made impeller that can't stand being hit by an occasional chunk of wood or a nut or bolt, whether they plan to use a pre-seperator or not, they have made a serious mistake.

[Adam Strong]

You are missing the point, my first point- Delta, Grizzly, etc. have been selling single stage dust collectors which have been safely used for 40 - 50 years (or more?) without pre-separators. What has changed all of the sudden that makes them dangerous ???? If they were dangerous to use without pre-separators the CPSC or other governmental outfit would have banned them in a heartbeat long ago!

Most of them have some sort of grid that will stop huge chunks of wood, but will not stop nuts, bolts and smaller chunks of wood from hitting the impeller. To cover themselves, Grizzly's manual says don't pick up metal. Fine, these are dust collectors anyway and for a number of other reasons you should clean your floors with a shopvac that has good static pressure, anyway. And, if somebody spends their hard earned money on a DC with a plastic or other poorly-made impeller that can't stand being hit by an occasional chunk of wood or a nut or bolt, whether they plan to use a pre-seperator or not, they have made a serious mistake.

I totally get that point, but as you state the manuals say not to suck up metal or large chunks of wood. This is legally how they cover them selves as it is an intended use issue at that point, but accidents happen. I just speak from experience of using a SS DC and fouling the impeller by unintentionally sucking up a chunk of wood. You make valid points, but no more or less valid than those I voice. It is my preference to have to not worry about a chunk of wood falling near the end of a hose and inadvertently getting to the impeller. The great thing about info found online is that you get multiple, correct, assessments of your options and can decide for yourself to be conservative or liberal in your plans. And yes, anything with a plastic impeller is junk.

[Alan Schaffter]

I totally get that point, but as you state the manuals say not to suck up metal or large chunks of wood. This is legally how they cover them selves as it is an intended use issue at that point, but accidents happen. I just speak from experience of using a SS DC and fouling the impeller by unintentionally sucking up a chunk of wood. You make valid points, but no more or less valid than those I voice. It is my preference to have to not worry about a chunk of wood falling near the end of a hose and inadvertently getting to the impeller. The great thing about info found online is that you get multiple, correct, assessments of your options and can decide for yourself to be conservative or liberal in your plans. And yes, anything with a plastic impeller is junk.

I am just trying to provide proven, workable but possibly unknown solutions to very common problems and complaints with DC's; to give people the benefit of what I have learned. Unless you have tried it, you will never fully appreciate the benefits of never having to empty a dust barrel. Believe me, it far outweighs and it is well worth the very remote chance of sucking up something that will damage the fan impeller. This is especially true if you typically plane large amounts of rough stock. There is no comparison between the difficult, messy, dirty and hazardous, dust-cloud-producing job dumping a full dust barrel five, six, or more times compared to changing out bags in a push-through system. I have done it both ways, believe me, I would never go back.

I know it restricts flow and can cause backups, but if you are worried about ingesting items that can potentially damage the impeller, you can always leave the protective grid (or part of it) most DC manufacturers put inside of the inlet to their single stage units. Or, like pot holes in the road, just try to avoid big items. From what I can tell reading many forums, most folks prefer to take the chance and remove the grid. I have a strong DC, that to quote a movie line, "will suck the chrome off a trailer hitch", but in normal woodworking do not ever suck up large objects. It is only when I am especially careless or intentionally do so, since even then, I have never suffered damage to my impeller.

One of these days I need to find the 18" long stick I dropped in my mitersaw DC port!

[Adam Strong]

I definitely agree about not having to empty a barrel of dust. I use a Thien type pre-separator with a bag. I built a simple steel hoop and frame that drops in to hold the bag in place and can be removed easily to simply tie up the bag and put it to the curb. I also have removed the crosshair grate in the intake, but with a pre-separator I have no worry of chunks making it into the throat. I use it to clean up the shop floor, which I would never do with a pass-thru type.

[Curt Harms]

at least with cyclones. According to Bill Pentz, it takes a larger diameter blower/more h.p. to get the same amount of air through a cyclone using the pull through configuration compared to a push through. If you had a marginal D.C. to start with, putting a pre-separator before the fan isn't going to help it any. I don't know how much flow loss is incurred with the Thien baffle. I'm guessing less loss than a cyclone but that is just a guess. This seems like a "ya pays yer money and ya takes yer chances" type thing. There are valid arguments on both sides.