DesignFind

I built a fume extraction duct for my enclosure and hung it from the ceiling of my garage.  Because I used the flexible coil type ducting, it would sag without support, so I built a track to hold it.

This design uses a type of plywood called "underlayment" with a 5.1mm thickness.  I like this plywood because it is very cheap, tough, and cuts well (with a 20w laser, I have consistent results with 5 passes at 85% power).  All the tabs, slots, and tenons assume a 5.1mm plywood thickness.

For hanging wire I used fishing line sufficient for catching large sharks and aluminum compression ferrules to make loops at each end.  Once you've figured out your hanging length, it is easy to make a bunch of cables all the exact same length for easy hanging.  Included in the design are also ceiling attachment sections.  These have notched slots so you can screw the ceiling bracket roughly in place and then find a good spot in the slot so the hanging cables hang vertically above the track tab to which they attach.

Assembly of the ceiling brackets is straightforward.  The pieces with a complicated side slide, one on each side, into a tenons at the ends of the bracket.  Because they go through a tenon, the load bearing piece cannot separate from the screw base, but this this means there is a gap between those wings -- the square pieces fill that gap.  It will make it easier to attach to the ceiling if you also glue the filler pieces underneath the pieces that go through the tenons.  The screw hole is optimized for self-tapping wood screws as pictured -- the particular brand I used is "Deckmate".

For the track itself, the spacers are inserted through the slots on on each side of the U shaped piece.  In this way, you can make a track as long as you need just by cutting more pieces.  You could if you wished, lengthen the spacers to cover more distance with fewer U's.  There are holes at the ends of the spacers that will mate up with each other.  Insert a ~4mm diameter rod through those holes and glue in place.  This makes it impossible for the section to separate even if there is a glue failure.  I should have used a more standard sized rod but I happen to have a bunch of sanding sticks of that diameter -- more than I'll probably ever use -- and so there it is -- 4mm holes.  One of the pictures shows the sanding stick.  These holes can be easily adjusted to whatever diameter rod you have in your own CAD program.  One nice thing about the 4mm rods, is that they are easy to cut with wire nippers once the glue has dried.  I didn't bother with sanding because -- well, you see my ceiling -- nothing is making that prettier.