Different ways of supporting the baffle?

[sploo]

In my never ending quest to think about building a Thien Separator (but never actually getting round to making one)...

I noticed that Cosmas Bauer has a separator design that has a completely circular baffle (no 120 degree section that's connected to the side of the separator body), and instead the baffle is supported by the outlet tube (which comes all the way down from the top and touches the baffle). He's cut away a section of the side of the outlet tube, as obviously the end is sealed against the baffle.

I can see that would be useful in stopping larger material getting caught on the leading edge of the larger (120 degree) segment of the baffle (as there is no larger segment - just a gap all the way round). However, I assume that drawing air from a cutaway at the side of the outlet tube would cause a lot of unwanted turbulence.

The original Thien design (pictured at http://www.jpthien.com/cy.htm) uses three rods coming down from the separator's top plate (to support the baffle). I assume they will catch longer (e.g. planer) shavings, and also affect airflow.

So... what I'm wondering about is to create a baffle with a slot/gap all the way round (i.e. a perfect circle), but supported by a single rod or pipe from the center of the underside of the baffle, which would be attached to the bottom of the collection bucket; basically a bucket with a tall table (with a round table top) sitting inside.

I assume the air speed in the center column underneath the baffle should be low/zero (i.e. the supporting pipe shouldn't affect airflow), and with a 1 1/2" (38mm) diameter metal pipe the baffle should be fairly rigid. A tapped hole in the top of the pipe would allow the baffle to be easily unscrewed for tipping waste out of the bucket, and the air outlet above could be a nice open bell mouth.

Does that sound like a good idea, or have a missed something?

PS I understand that a thin material for the baffle is a good idea. With the baffle supported from the middle of the underside, it should sag less than when it's supported from the side by a 120 degree segment, so it would be interesting to find some really thin sheet materials (1/16" aluminium, or carbon fiber). With it attached by just a single screw from the top it'd be easy to test out different slot gaps and baffle thicknesses.

[retired2]

I suggest you contact ??? and ask him how it is working.  Only people that have tried it know for sure, and I don't know of anyone who has tried it.

I'm guessing it doesn't work.  Good ideas spread fast, bad ones die quickly.

Unless you just love to experiment, I'd stick with a  design that works.

[nucww]

Too much opening leads to too much flow in the lower collector.  I used a spiral design and only had about 30degrees closed. I was getting too much flow in the lower can.  The dust in the lower can was all in the center rather than the outside.  I closed it back to about 120 and it seems better.  I agree with R2 stay with the 120.  The turbulent entrance expands into the upper cavity before it has a chance to expand into the lower can.

[dabullseye]

i  just use a 1/4" hard board that is beveled back on the bottom side. the slot where it meets the 120 degree section has radius on the end of slot and is smooth. when r2 was building his top hat i had suggested maybe bolting a rod to bottom of trash can so the baffle could rest against it. so thinking of your idea  maybe you could make a sleeve that fits over the rod but has a magnet in it to hold baffle in place and then you could remove it to empty the can. but i believe in KISS method and would just go with the proven method and use the hardboard. ive never had a problem with mine

[sploo]

I suggest you contact ??? and ask him how it is working.  Only people that have tried it know for sure, and I don't know of anyone who has tried it.

I'm guessing it doesn't work.  Good ideas spread fast, bad ones die quickly.

Unless you just love to experiment, I'd stick with a  design that works.

You mean Cosmas? I did contact him to ask where he got the design for the side opening in the outlet tube (and how it worked) but I didn't get a particularly clear response.

Too much opening leads to too much flow in the lower collector.  I used a spiral design and only had about 30degrees closed. I was getting too much flow in the lower can.  The dust in the lower can was all in the center rather than the outside.  I closed it back to about 120 and it seems better.  I agree with R2 stay with the 120.  The turbulent entrance expands into the upper cavity before it has a chance to expand into the lower can.

That's a good point. I was thinking of a double height top hat design - meaning the inlet would be flush with the underside of the separator chamber ceiling. I assume then that airflow coming in from the inlet shouldn't immediately lift material from the lower can even if there wasn't a closed area underneath. However, an easily replaceable baffle would allow the addition of a 120 degree wider area.

Has anyone tried out different slot gap widths? I assume that a thin gap will plug with planer shavings, but is there a separation efficiency benefit of a thin gap for most normal cutting?

i  just use a 1/4" hard board that is beveled back on the bottom side. the slot where it meets the 120 degree section has radius on the end of slot and is smooth. when r2 was building his top hat i had suggested maybe bolting a rod to bottom of trash can so the baffle could rest against it. so thinking of your idea  maybe you could make a sleeve that fits over the rod but has a magnet in it to hold baffle in place and then you could remove it to empty the can. but i believe in KISS method and would just go with the proven method and use the hardboard. ive never had a problem with mine

1/4" hard board would be easy to source, so that sounds fine.

I was thinking of a tapped hole in the top of the pipe for a bolt, which would take a matter of seconds to remove.

[hacknbuild]

I am going to play around a bit with a center column of PVC.  The basic idea is to cut a large slot or slots in the top portion of the pipe and use a coupler to attach it.  It makes the build a little more simple, and I already have all the PVC from another project.  To see how well it works, I will compare the performance to the Oneida Dust Deputy which I've been pretty happy with.   I plan on keeping the other aspects of the design the same.