DC question

[jussi]

So as suggested by some here I decided to go with the S&D piping. But I noticed they're bigger than blast gates and ports of the machines. What did you guys use to make up the gap? Any pics? Preferably close ups of how the blast gates and machine ports are connected. Thanks.

[LarryG]

Some old threads that should be helpful:

Here is an overview of my hard-pipe system as it was originally installed (in a building I no longer have use of, but that's another story). Includes 12 pictures.

An older thread containing discussion on system layout, including how to make up the various transitions. In particular, look at post #15 by Tom Miller.

A thread started by dbhost, again containing discussion on connections and transitions. See my posts #3 and #14, and read the replies from everyone else, too -- some good stuff in there.

And on a related topic, this thread shows my stovepipe mod, which you should consider doing if your particular DC unit will support it.

There are other old threads out there but a careful reading of these should answer most of your questions.

[JimD]

To connect flexible pipe to 4 inch S&D, I force fit the flexible inside the coupling part of the S&D. One end is flared to go over the pipe diameter and I was able to force the flexible into it.

I do not like the plastic blast gates so I made my own of wood. They are simple sandwiches of 3 pieces of plywood with the center piece sliding. The outboard parts of the center piece must be slightly thicker to permit the sliding to occur. I used pieces of old business cards to shim them out (test with clamps without glue and then glue up). There are several advantages of these homemade gates including lower cost (if you use scrap), they open and close completely (the plastic ones do not open all the way), and they do not get plugged up by sawdust. The latter was my main objection to the plastic gates. I have some wall mounted and some just in the pipe. I like using 1/2 a coupling for the S&D pipe in the two outside pieces of the sandwich (you could use a whole coupling, I am just cheap so I split it into two pieces) to join to the pipe. You need an adjustable hole saw in a drill press to easily make these gates because you need to be able to make holes the size of the pieces you want to use as couplings. I use a cheap one from HF which doesn't work great but works.

Jim

[jussi]

One more question. Is it vital that the connections be glued? I have a habit of never being quite happy with my shop layout and will probably be moving the equipment around in the future. Plus I may want to experiment with different configurations of the piping itself to get maximum efficiency.

[Uncle Cracker]

You can use some silicone in a caulking gun and seal from the outside. That way, you can just peel the silicone off if you want to change something. I have used dry press-fits on all my connections (except for one that didn't line up right) with no problems, but I do strap both the pipe and the fitting at connections.

[LarryG]

No, not vital -- in fact you generally do NOT want the connections glued for precisely those reasons.

Where there is a minor air leak because a given fitting is not an exact match for its mate, seal the joint with duct tape, or sealant as UC suggests. Where the various pieces gradually come adrift because of vibration or gravity, secure the joint using either duct tape, or two or three sheet metal screws spaced equidistant around the joint. I used the latter solution with my system, and it worked very well. Just be sure to use some really tiny screws (I used 1/4" at most locations, 3/8" at a few) so the points won't protrude into the airstream; and use a light touch when you drive them, as the plastic pipe and fittings will strip out easily.

[jussi]

Ok it's coming along but I have another question. In terms of efficiency, is it better to put the blast gates closer to the tool or the DC? Here is the situation I have below. Should I put the gates in the yellow position or red? Or does it matter?

[LarryG]

Most expert sources I've read/seen/heard, including Bill Pentz, say to put them in the red position -- that you want the DC sucking on as little empty pipe as possible when the blast gate controlling an inactive branch is closed. Quoting Pentz: "The best place to put your blast gates is next to the wyes off your main line up high."

But you would certainly want to temper this with convenience. If you had a 10' high ceiling you wouldn't want to climb a ladder every time you needed to open or close a gate.

[jussi]

Thanks Larry. This particular connection is on the ground so I guess I'll put them near the wyes

[Uncle Cracker]

Putting them in the red position will result in less stagnant chip clutter in the runs, particularly on the lesser-used ones. As LarryG pointed out, it's sometimes just not practical on overhead piping, though, so it helps to use true wyes for branches wherever you can.

[jussi]

Putting them in the red position will result in less stagnant chip clutter in the runs, particularly on the lesser-used ones. As LarryG pointed out, it's sometimes just not practical on overhead piping, though, so it helps to use true wyes for branches wherever you can.

Yah it would be so much easier to use Tees. I'm also trying to use 2-45 elbows instead of a 90's. Makes runs longer and look like a bad lego accident but I hope it helps with air flow.

[jussi]

I got these metal blast gates from Rockler. I'm not sure I didn't notice them earlier but they have slits on the bottom which, when the gates are open, leave an open gap. 2 questions.

1. Why are they there? I have some Rockler plastic gates I got a while back and they didn't have them.

2. Is this going to be a problem? EDIT: Wouldn't this lower the efficiency of the DC? Should I just silicone the slit?

[phi1l]

2. Is this going to be a problem? It seems like it's going to let alot of the fine dust get out.

Well assuming it is on the vacuum side, fines won't get out but you will have some air leaking in.

[jussi]

Well assuming it is on the vacuum side, fines won't get out but you will have some air leaking in.

Doh!! Of course you're right. What I should have asked was wouldn't the slits lower the efficiency of the the DC?

[Nil]

They might let a little air in... They seem to be an odd design if they pull out of that slit completely (when open) and let air in through there... I would have thought they'd be like the metal blast gate at the bottom of this page (http://www.ptreeusa.com/blastgates.htm) where there is still some metal filling the slit even when the gate is open...

The slits are there to cause the blast gate to be "self cleaning." Gate that don't have that slit usually collect sawdust in the slot over time, preventing the gate from fully closing...