DC in a box, exhaust air?

[retired2]

Thanks everyone for the inputs.  After doing a bit more reading about what makes a good top-hat design, I'm becoming convinced that I shouldn't use the dc ring - mostly because of the 6" round inlet that would be blowing in only 1" away from the 6" outlet, making bypass much more likely.

So, my plans now include making a top-hat with a 6" round to 8"x4" transition (13% larger cross-section for the rectangle).  I would make the rectangle taller and narrower, but that would increase the height.

I'd like to have the outlet at least even with the bottom of the inlet, so the tophat should be 11-12" tall.  With a 1.5H tophat, I recall some issues with bellmouth outlets (Mike F http://www.jpthien.com/smf/index.php?topic=1110.msg6292#msg6292), so I'm leaning toward a straight outlet with air-straighteners (t8/t12 bulb protectors).

I see that Retired2's tophat is 1H.  Is there any evidence that other than height, there is any drawback to making the tophat taller than the inlet?  I guess if I wanted to make the rectangle of my transition taller and narrower, I could make the overall height the same or slightly taller than the inlet.  I wonder which would be better...a 12" TH with an 8"x4" inlet or a 10" TH with a 10"x3.2" inlet?

As far as enclosing everything for noise-reduction, I'm going to try it without enclosure first and see how tolerable it is (I haven't had DC before, just recently picked up the used delta unit).  I may try an insulated hvac duct from the blower to the filter for the first step in noise reduction.

You will be very surprised as to how much air the unit needs. I enclosed my air compressor in an area about 3x3x10 and installed a vent and fan to ensure it did not get too hot after using it quite a bit one day without the vent. The fan comes on when the air compressor comes on. Do the same for your enclosed unit.

If I do end up enclosing, this was my concern.  However, the case of an air compressor vs a DC is a bit different, since the DC pulls ambient air into the box and if it flows across the motor, it should act like a very strong fan (or so my theory goes).  We'll see if I ever test that theory.

Thanks again for the ideas and thoughts... this site makes for some interesting reading on a topic I've never thought much about before.

A bell-mouth does gather air from the spread of it's flange, so depending on your chamber diameter and your outlet pipe size, it can increase the amount of bypass.  Since my bell mouth is 5", I have only had a small amount of fines make it to my second stage.

There is an article I posted several times with tests of various Dust Collectors.  In that article there is an inset that describes the benefits of bell mouth inlets.  The bell mouths described are not the wide flanged version we've all been using for outlet pipes on our separators.  The ones described in this article are merely inlets with the entry rounded over by whatever method you choose - router bit, wood rasp, etc.  The point is almost any radiused inlet is more efficient than a straight pipe. 

I'll never be able to find it, but someone on this site glued up several rings of mdf, then rounded them over with a rasp to make a bell mouth.   It wasn't pretty, but it was inexpensive, more efficient than a straight pipe, and did not have the huge flange that can cause problems, especially if it is a commercial 6" bell mouth.

[RonP]

That report sounds interesting and I would very much like to read it. Can anyone point to it?

I think this might be what you're looking for:

http://www.jpthien.com/smf/index.php?topic=1141.0

[hweaver2]

Here's a though on mounting your Wynn filter instead of a box for the filter, why not try this adaptation of this mounting.

[retired2]

Here's a though on mounting your Wynn filter instead of a box for the filter, why not try this adaptation of this mounting.

It's a nice job, but I would have figured out a way to soften that 90 degree hose bend into the filter. 

[kerrybp]

Yes, that's my general idea, going directly from the blower to the filter without a second ring.  The filter is not in a box by itself, the box idea was to enclose everything for sound deadening, but I may not pursue that idea.  I'm working slowly on it when I get a few minutes here and there - have the round to rectangle transition done, all the tophat components cut out, and will hopefully get the tophat assembled in the next day or so.  One thing I'm pretty positive about is that my original notion of making the tophat out of the DC ring would have been a LOT less effort.  I guess I've learned a bit about cutting out circles, though...including using the smallest diameter bit to cut down on the wood/mdf/hardboard dust flying around.  It's pretty ironic the amount of dust I've created making something to collect dust.

[kerrybp]

First of all, thank you to Phil and all who have contributed to this baffle / top-hat design.  I've borrowed/stolen many ideas from several of you (especially retired2) to put together my separator, so thank you.

I finally finished enough of my tophat system to give it a test run.  The results were mixed - I think there's still some tweaking to do.  I ran it without the filter and only see bypass if I put a lot of dust through at a time...more than would typically come from a machine, I think.  The odd thing I see is that a lot of the dust goes up and spins around the top of the chamber instead of being pulled in a spiral down to the slot.  My separator is 12" tall with the bellmouth 3" from the bottom.  The inlet is 9.5" tall by 3.5" wide and is flush to the top of the chamber.

One thing I see is that the hardboard baffle, though partially supported with plywood beneath, is being pulled up by the suction in the chamber, so I wonder if that's creating an upward air ramp (or maybe it's the result of something else pulling air upward).  I will probably try adding a dowel or threaded rod to keep the baffle from rising to see if it helps, but if anyone has seen this before and has ideas on fixing it, I'd appreciate the input.

I've attached a few pictures of what I have so far (haven't attached the filter and clean-out yet).  I didn't take photos at every step of the construction, so the pictures don't show everything, but the general idea is there.  I did make a bellmouth from plywood/mdf and the largest round-over bit I have (3/4 R) and added T12/T8 bulb protectors to the outlet for air straighteners.