Internal baffle for 1.5 hp dust collector

[wilburpan]

I have a question before making an internal baffle for my 1.5 hp DC. (It's a JDS model, in case anyone cares.) When I compare the design of a typical internal baffle:



to the original Thien baffle:



it seems that the role of the center port in the top part of the original Thien baffle is played by the conical metal rim in the dust collector.

Clearly, the diameter of the metal rim in the dust collector is a lot wider than the port in the original Thien baffle. Does that affect the efficiency of the internal baffle? And would it be better to fit a piece of plywood with a smaller port opening into the opening of the metal rim?

I know that it will be more work to fabricate the second piece, but I'd rather take my dust collector apart just one time.  :D

[phil (admin)]

The center opening in the funnel of your DC will be larger, but it needs to be in order to move enough air volume to your filter w/o too much resistance.

So typically that opening in the funnel is what we rely on as a substitute for the center port.

HOWEVER, I have seen some units with huge center openings, and some with upside down funnels, and some with no funnel at all.

I guess my rule of thumb would be that the center opening should be one to three inches larger than the inlet.  Much larger than that shouldn't be necessary, and would possibly compromise separation.

Some people make a chimney (sometimes with an old coffee can with both ends cut off) that fits through the opening and provides more of a lip down below.  This typically improves separation.

[wilburpan]

The center opening in the funnel of your DC will be larger, but it needs to be in order to move enough air volume to your filter w/o too much resistance.

True, but if I made a stand-alone preseparator, wouldn't that also cause a similar increase in resistance? I read elsewhere on this forum that resistance either pre- or post-impeller is the same regardless.

I guess my rule of thumb would be that the center opening should be one to three inches larger than the inlet.  Much larger than that shouldn't be necessary, and would possibly compromise separation.

Some people make a chimney (sometimes with an old coffee can with both ends cut off) that fits through the opening and provides more of a lip down below.  This typically improves separation.

I guess I'll see what the opening looks like when I get my DC apart. I don't plan on narrowing the center hole to be smaller than the intake to that part of the DC, for sure.