Space between input port, top, and baffle

[pawolf]

I'm about to embark on creating a "classic" Thien Separator using a 10-gallon steel garbage can I picked up at Fleet Farm.  I will use it with a shop vac, and tools such as a random-orbit sander, router, portable table saw, etc.  I have a tendency to over-think things, as I'm guessing a lot of us on this board tend to do.

Anyways, my first question has to do with the amount of space to leave above and below the input port.  If I read the text and look at the pictures at http://www.jpthien.com/jpthien/cy.htm and http://www.jpthien.com/smf/index.php?topic=7.0,  the elbow appears to be touching the bottom surface of the separator top, and ~3/4" above the baffle.  However, reading the discussion at http://www.jpthien.com/smf/index.php?topic=151.0, Phil says to leave 1/2" - 1" both above and below.  Is leaving space both above and below the elbow still the current thought?

My second question is also related to the elbow.  Everything I read says to use a 90-degree elbow.  I ordered the 2 1/2" universal dust ports from Rockler but haven't received them yet.  It appears from the pictures the port meets the flange at a 60-degree angle or so.  Would it make sense to use a 60-degree elbow, which I saw at Home Depot to "straighten" the input a bit?  I would keep the horizontal leg of the elbow parallel with the baffle, and the vertical leg would then exit the top at an angle approximately the same as the dust port.  Or is 90-degrees the way to go?

My third question, and the last one for now, has to do with the baffle itself.  The information at http://www.jpthien.com/smf/index.php?topic=10.0 says to use 1/8" hardboard.  I also read a couple of other discussions that at some point, a thicker baffle will reduce separation.  Is 1/8" hardboard still the current thought?  Also, should the edge of the 240-degree "drop slot" be left square, or would it be better to round it over?

Thank you.  I'm sure I'll have more questions as I proceed, but this is all I have for now.  I'll be sure to take pictures as I go and post them when finished.

[phil (admin)]

I'm about to embark on creating a "classic" Thien Separator using a 10-gallon steel garbage can I picked up at Fleet Farm.  I will use it with a shop vac, and tools such as a random-orbit sander, router, portable table saw, etc.  I have a tendency to over-think things, as I'm guessing a lot of us on this board tend to do.

Us?  No!!!

Anyways, my first question has to do with the amount of space to leave above and below the input port.  If I read the text and look at the pictures at http://www.jpthien.com/jpthien/cy.htm and http://www.jpthien.com/smf/index.php?topic=7.0,  the elbow appears to be touching the bottom surface of the separator top, and ~3/4" above the baffle.  However, reading the discussion at http://www.jpthien.com/smf/index.php?topic=151.0, Phil says to leave 1/2" - 1" both above and below.  Is leaving space both above and below the elbow still the current thought?

Leaving some space will prevent debris from getting caught.  Probably .5" is enough.

My second question is also related to the elbow.  Everything I read says to use a 90-degree elbow.  I ordered the 2 1/2" universal dust ports from Rockler but haven't received them yet.  It appears from the pictures the port meets the flange at a 60-degree angle or so.  Would it make sense to use a 60-degree elbow, which I saw at Home Depot to "straighten" the input a bit?  I would keep the horizontal leg of the elbow parallel with the baffle, and the vertical leg would then exit the top at an angle approximately the same as the dust port.  Or is 90-degrees the way to go?

As long as the incoming air is horizonal to the baffle, a 60-degree elbow would be okay.  But you might find it difficult to get a 60-degree elbow mounted into the top so the exit is 90-degrees to the baffle.  In any event, I don't think you'd gain much, as shop vacs can easily handle a 90-degree bend.

My third question, and the last one for now, has to do with the baffle itself.  The information at http://www.jpthien.com/smf/index.php?topic=10.0 says to use 1/8" hardboard.  I also read a couple of other discussions that at some point, a thicker baffle will reduce separation.  Is 1/8" hardboard still the current thought?  Also, should the edge of the 240-degree "drop slot" be left square, or would it be better to round it over?

Thinner is better.  I use 1/8", never more than 1/4" hardboard.  I use the hardboard that is smooth on both sides, which I get at my lumber yard (they don't have it at HD/Lowes).  And no real need to round anything over.

Thank you.  I'm sure I'll have more questions as I proceed, but this is all I have for now.  I'll be sure to take pictures as I go and post them when finished.

[pawolf]

Phil,
Thanks for the uber-quick reply.  After thinking about it more, I have to agree with you that getting the 60-degree elbow mounted so the exit is oriented correctly might be a bit of a challenge and require a fair amount of trial and error.

Chuck,
I thought a lot about designing a side-inlet.  From my understanding of things, I think there would be more to gain from this design if I was using a dust collector rather than a shop vac.  In addition, I think this would be easier to build with a cylindrical container (e.g., cement form tube) rather than a conical container (garbage can)  I'm sure there would be some gain, but for now, am going to follow Phil's 90-10 rule and go with the original design.

[pawolf]

No pictures yet, but the separator is complete.  Nothing fancy, looks a lot like the pictures on this site.  Ran a quick test with a pile of wood chips/shavings/sawdust.  Virtually everything other than a little dust ended up in the separator.  Same for when I connected it to my ROS and did a little sanding.  I've since put a dust bag and HEPA filter in my shop vac.  Am looking forward to finding some time to really use this.  Phil, thanks again for your design and providing this site for discussion.