# Thien baffle questions



## JerryinCreek (May 11, 2013)

Ready to build my separator with Thien baffle but have a few questions:

1) Should the inlet elbow rest ON the baffle or be located above it?

2) I was planning to build the baffle using 1/4" hardboard, tempered both sides. But, was wondering if this slick surface would be less effective than using material with a rough surface? My question is whether the rough surface friction would slow the particles more and make the baffle more effective?

3) Has anyone experimented with the length of the center inlet (space between it and the baffle)?


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## ajosephg (Aug 25, 2008)

It's been a long time since I built mine, so I've forgotten many of the design principles. I'd recommend that you peruse Phil Thien's website. http://www.jpthien.com/.

In my opinion, which isn't worth much:
1. It doesn't make any difference whether the intake touches the baffle or not.
2. The smoothness of the baffle doesn't make a big difference, as my thought are that the particles colliding with the walls of the container and the resulting loss of the airstream velocity is what causes the particles to drop out. I used pretty rough floor underlayment for mine, and it works fine.
3. I don't know about any experiments.


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## ajosephg (Aug 25, 2008)

It's been a long time since I built mine, so I've forgotten many of the design principles. I'd recommend that you peruse Phil Thien's website. http://www.jpthien.com/.

In my opinion, which isn't worth much:
1. It doesn't make any difference whether the intake touches the baffle or not.
2. The smoothness of the baffle doesn't make a big difference, as my thought are that the particles colliding with the walls of the container and the resulting loss of the airstream velocity is what causes the particles to drop out. I used pretty rough floor underlayment for mine, and it works fine.
3. I don't know about any experiments.


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## todd1962 (Oct 23, 2013)

Is this a tophat baffle?


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## JerryinCreek (May 11, 2013)

Joe - thanks for your input.

Todd - yes, I believe it would be a tophat baffle. I am mounting it under the lid of a plastic drum with a center inlet feeding into my Delta DC.


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## rum (Apr 28, 2011)

1) If you're doing a top hat, I'd recommend the side feed setup into the side of the top hat. That avoids having another bend in the air stream and minimizes the places where you're adding turbulence. Its not a whole lot harder to do. Actually if you're mounting it under the drum lid its not exactly a top hat, but you could still mount the inlet into the side of the drum pretty easily (might need a little re-enforcement on the outside).

2. smoother is probably in general better imho, although where it really seems to matter is around the slot. I have the inside of my thien top hat skinned with sheet metal and it works pretty dang good. The one gotcha spot I ran into was I had some rough spots around the edges of the slot (especially where the slot stops/starts) and stringier bits (like from the planer) would get caught there. A little quality time spent with a file and s stone fixed that up so I no longer have problems but not before I had a few gum ups.

3) yes - it needs to be far enough up that it has good airflow but not so far it promotes bypass. The actual "perffect" distance depends on the size of the tube and the size of the baffle in some complex way that I can't pretend to explain. I made mine easy enough to pull apart and adjust if need be and stuck it in so there was a smidge less than 4" and it seemed to work pretty well (this was with a 5" pipe). There was a whole series of experiments with using bell mouths for that (significant airflow improvement) and air "straighteners" (measurable improvement) on phils' forum. Some of the threads over there were interesting in their own right.


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## JerryinCreek (May 11, 2013)

rum - Thanks so much for your response!
I appreciate the thought you put into your answers.
-I didn't see any examples of a side feed but that makes a lot of sense.
-I was wondering about some type of sheet metal work around the open area of the baffle. Do you know of any photos/examples available?
-Good call on the inlet distance - making it adjustable is a great way to go.
Thank you!


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## HillbillyShooter (Feb 15, 2012)

Check out this web site for a great tutorial on building a Thein Separator: http://www.freeforum101.com/charlesneil/viewtopic.php?p=11836&mforum=charlesneil#11836

1. I located the elbow above the actual baffle and centered between the baffle and the top.

2. My sides are kerfed 3/4" plywood with Formica lining the inside.

3. No, I just followed Pitbull's tutorial.

My advise is to not over think it, just follow a proven design. And, my unit works perfectly. You can check out my recent post if you missed it, http://lumberjocks.com/projects/102418

Best wishes and enjoy.


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## JerryinCreek (May 11, 2013)

HillbillyShooter: I will check it now - thanks your input! Yes, over-thinking it is part & parcel of me!


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## HillbillyShooter (Feb 15, 2012)

Since it takes one to know one, you can understand how I can relate to your post, ergo the reason for my advice. I spent several years agonizing over the construction of a Thein, and finally just did it. Surprise, it worked and it wasn't that complicated.


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## rum (Apr 28, 2011)

Jerry, there are some decent posts on some of the sheet metal work over on Phils site. I didn't do anything super special there myself, as I just used a piece of 5" stovepipe as the inlet into the side of the baffle, and nibbled it away so it didn't stick in to far. I don't really know how much difference that makes but it seemed to make sense to me at the time anyway 

I suspect that skinning the bottom (floor) of the baffle was overkill though (heh).

one other note: the thinner the baffle the better up until it starts to flex. I started out using a 3/4" piece of plywood for the baffle itself and figured that beveling the underside and skinning the top would suffice (which was why I skinned the top with sheet metal to start with) - definitely got THAT wrong! I ended up thinning it down to 1/4" and imho would have been even better if a bit thinner. Live and learn


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## JerryinCreek (May 11, 2013)

Thanks rum - especially the comments on the baffle thickness. I will check Phil's site!


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