OK. So, after painting a car in my garage and dealing with the ridiculousness of clear coat, I decided it was time for some proper shop air cleaning. My garage is almost always dusty and I hate being a subscriber to the black booger club.
So, with a furnace blower that a friend got me a few years ago (for this purpose), I set about getting it wired up. It's a 4-speed fan, but I chose to only use 3 speeds. I'm not heart-set on this setup and may just do a beefy variable switch for the "high" speed as my electrician buddy thinks startups will burn this 20A (15A max per pole) out. Time will tell.
Once I got the electrical working, I set about to starting on the box. a Sheet of 1/2" plywood and a bunch of scraps to the rescue.
Fitting the blower inside the box
I realized that my original design had dimensions of 18"x24", which there are no panel filters on the market for, so I modified the filter end to accept 16x24" panels.
Shots of the finished box
Now, normally, I'd just have a cold-air return grate attached to the outside of the box when it's acting as an air cleaner/circulator. But, I tried painting a car in the garage, which left a lot of fumes and particulate in the air; especially with clear coat, and I think I gave myself a bit of black lung from the floaties last time, so I wanted to be able to duct this to the outside as well. To do that, I picked up a bunch of 5" ducting and will punch a hole in an outside wall. I also started on an adapter to take the 5" and connect it up
Valved bit taped on to help keep alignment for stapling the duct to the board.
Stapled in securely. I'll be adding silver ducting tape to seal this all up.
Annnnnd mounted over the exhaust side of the cleaner.