Help with tophat design

[RobHannon]

So I am trying to iron out the last few details on a tophat for a 55gal drum.

Inlet is the 10"x 4" to 6" round HVAC fitting going into a chamber that is 18" tall and 20" in diameter. The base has an oversized slot and 4 large holes in the middle for light to go into the bin below. On top of that base will be an acrylic disk to cover the slot and holes. My thinking is I can start with a narrow dust slot and tune it. Outlet to the blower is 6" and will have a bellmouth and straightener mimicking Retired's design.

Am I wrong in putting the inlet fitting as close to the top of the baffle as possible?

How far down should I start the bellmouth with a chamber this large?


Going to attempt to upload a drawing of where I am so far.

[retired2]

So I am trying to iron out the last few details on a tophat for a 55gal drum.

Inlet is the 10"x 4" to 6" round HVAC fitting going into a chamber that is 18" tall and 20" in diameter. The base has an oversized slot and 4 large holes in the middle for light to go into the bin below. On top of that base will be an acrylic disk to cover the slot and holes. My thinking is I can start with a narrow dust slot and tune it. Outlet to the blower is 6" and will have a bellmouth and straightener mimicking Retired's design.

Am I wrong in putting the inlet fitting as close to the top of the baffle as possible?

How far down should I start the bellmouth with a chamber this large?


Going to attempt to upload a drawing of where I am so far.

Since I've never built a double high separator I may not be the best to answer, but here is my two cents.  Put the rectangular entry duct at the top just as you have it.  Make the depth of the outlet adjustable so you can experiment, but start with it at the bottom of the inlet, i.e. 10". Down.

[will1983]

One query, you seem to have a 9" high area below the inlet that appears to be outside of the circular air path I think this will result in a lot of turbulence .

If you intend for the inlet to be the full height of the chamber you will need to make the transition go from the round to the full rectangular height gradually. Your current design shows it stepping down.

[RobHannon]

Yes this is another of my design dilemmas.  I can either transition it down or extend the laminate/plexi sides further around in a spiral shape. NucWW posted a spiral design with a straightener that I may try.