Thread: Thien baffle Festool separator design

I've been messing around with designing a pre-separator for my Fe$tool vac so that I can replace the ungainly double-bucket perched on top of the vac. I expect it'll cost me around $499 less than Festool's CT-cyclone. It's all going to go into a systainer-size box, with a bin below and all locked into the top of the vac by the systainer connections.

Festool_Thein_Baffle_2020-Sep-29_12-12-42AM-000_CustomizedView21066124386_png.jpg

There are a few design choices/questions along the way - I suspect that the answer may be that no-one has done Bill Pentz-level investigation of these things, so it's all just a matter of winging it and seeing how it goes. There are however, several dust-obsessives here who may have some valuable insight...

So, basic baffle plan from the internets:

Thien diagram.JPG

Q1: Slot width seems to be around 3cm, and 240 deg of the circle. I can't find any reasoning behind these figures, beyond that it seems to be a 'sweet spot'. Anyone have any insight/suggestions here?
Q2: Where the slot starts relative to the intake - most people seem to put the intake at the top of the diagram above - a mirror of the red box whoever drew that original. I've put mine at the 90 deg mark of the circle. Any science about whether this is ideal or needs to be changed?
Q3: Is around the Vac connection - the bit that takes the air/fine dust from the 'cyclone' to the vac. Option 1, used by people like Marius Hornberger -tend to have have an impeller mounted above the separator, but I've seen this with vacs as well:

Festool_Thein_Baffle_2020-Sep-28_10-25-27PM-000_CustomizedView15507918588_png.jpg

It's just a simple outlet at the top of the cyclone.

Option 2 has a pipe descending into the cyclone, with an opening towards the bottom (and then an additional question of the orientation of that opening compared to the intake):

Festool_Thein_Baffle_2020-Sep-28_11-47-52PM-000_CustomizedView9212467128_png.jpg

Anyone have any ideas about pro's and cons of each (apart from simplicity of construction)?

Incidentally, Festool's cyclone uses the pipe down into the cyclone arrangement. Their slot is all the way around, with the baffle dangling off the pipe. This may just be to simplify manufacturing and construction (I wouldn't think a company that makes recurring income from selling vac bags has too much incentive to make their separator super-efficient, but maybe I'm just cynical and unkind).

Screen Shot 2020-09-29 at 10.53.55.jpg

Any thoughts, insights, ideas and suggestions appreciated.