I just picked up a DC 28 for five bucks. It was clogged and one of the cams was broken. I searched Youtube and came across this video. I think the guy in the video explains it well. The air muscle is used to hold the nozzle closer to the carpet (which is where the tubes go) it's vacuum controlled. It's an over engineered Dyson but does clean fairly well and grooms the carpet better than any Dyson I've owned. I took my air compressor and blew out the underside and the cyclone which is all you can do without getting really complicated.