Reply by crank49

In its simplest form a drop-out-box is just a drum, with a lid and two duct connections. One inlet and one outlet.Heavy dust enters the drum at high speed and as the area of the drum is much larger than the duct the velocity drops very low. This causes the heavy particles to be overcome by gravity and fall to the bottom of the drum. The lighter, very fine dust and the air then re- accelerates into the outlet duct, leaving the heavy stuff behind. Not as effecient at dust removal as a cyclone, but does not create as much pressure loss. It takes energy to spin the flow into a vortex in a true cyclone.

Here is a link to another jock who built one based on plans in ShopNotes Magazine.
http://lumberjocks.com/projects/61326

-- Michael :-{| Diapers and politicians both need to be changed often; and for the same reason.