Interesting write-up on a simple and small dust collector. I built myself a simple dust collector out of PVC and an old bucket to help get all the sand out of my sand filter (for my pool). It works great and I never see a bit of sand in the shop vac. Not sure how well something this small would work, but its worth noting it for future reference. I like the use of a bike innertube for connectors.
http://www.instructables.com/id/PET-Bottle-Cyclonic-Dust-Separator/