I hadn’t thought of calculating the mph, but it seems intuitively useful. I think 3 or 4 mph is average walking speed for a human. That seems like the lower bound for what I’d expect to be effective.
I’m pretty good at calculating, too, once I have an idea what I’m looking for, so I did this:
Assume my DC (advertised at 650cfm) is close to 550 after a short hose and the bag. That means I’d have to shrink my table to something like 12x20 or 15x15 and make enough holes to not slow it down any more. Since the inlet hose is already about 4in diameter, anything over 13 sq inches might be enough holes. That could actually be a useful size.
Getting up to that speed with two box fans would require about a 20x20 table, which is the same size as a single fan, so not large enough to not slow the fans down even more. If i could do with half that speed, the box fans become workable, but then the dust collector could support a table only slightly smaller with no extra filters or cleanup, and it’s ok if my assumptions are off a little.
I think I’ll go look for videos where anyone might have actually measured real cfm under any of these restrictions for the portable dust collectors and box fans.