This seems to hardly ever come up, even on a woodworking forum I frequent it's not brought up very often. I have two shopvacs, one for each room of my shop for general clean up, but when I got larger sized tools, the shopvacs didn't do much so I thought about a real dust collector. I looked into one of these, but when I asked the salesman at the store if it could be mounted on a wall, he said no. Space was an issue, so I couldn't go with the regular design of dust collector, even with it's small foot print.
I decided to make one. My dad gave me a large squirrel cage motor from a restaurant's oven hood, which I'm assuming is explosion proof because it was covered with grease. The opening of the intake was 6", and needed to be stepped down to 4". I couldn't find any adaptors at tool outlets, so I used plumbing fixtures and LOTS of silicone. On the outtake, at first I installed a little filter cartidge that screwed right into the end where I had a plumbing fixture fastened, but I found it blocked too much air - dust collectors can only suck in as much air as they can blow out - so I changed my setup to what is pictured below. I have the outtake running into a garbage can. Inside the garbage can I have a cone made of paper. My theory is the cone creates a vortex and traps most of the dust, and what escapes gets caught by the furnace filter.
Image 1
Image 2
This is how I have the motor mounted.
Image 3
Here is the filter.
Image 4
Image 5
Here is the inside.
Image 6
My idea behind the cone.
When I took these pictures, it was the first time opening up the can since constructing it. There is a good amount of sawdust in the very bottom, which would have otherwise been all over my shop. I also found it necessary NOT to touch the furnace filter, as with use a layer of dust builds up, further blocking dust from escaping, and touching it caused clouds to puff up when I would then turn on the machine.
You may think the garbage can takes up as much room as one of those dust collectors, but not really, plus it only cost me about $50 to make.
BTW, it's quite as hell.