Some people add these cyclone things to there shop vac and is wondering what it does other than adding space and watching the wood go in circles. My best guess is it takes the bigger chips of wood and it falls in the cyclone but the dust goes to the vac. Or it somehow allows the shop vac to run longer? If there is benefits would it be a nice accessory to get?
For detailed information about how they work, check out the wikipedia article. Basically:
Rotational effects and gravity are used to separate mixtures of solids and fluids. The method can also be used to separate fine droplets of liquid from a gaseous stream.
The shop-vac creates suction at the top center of an upside down cone. Matter enters from the side. However, large particles, because of their momentum, mass, and centrifugal force, instead of going straight through to the vacuum, spin around the walls of the cone instead, eventually just falling out a hole in the bottom into the bucket.
Here is a nice demo: https://www.youtube.com/watch?v=v2ALTK6d07A.
I have one and it's great. Instead of cleaning out filters virtually daily, I shake them out every... 2-3 months tops, and even then it's only really fine dust, unlike the inches of caked on crud that usually collects on the filter. The cyclone pulls all the large particles and a good % of dust out into a bucket first, so the filter stays clean and suction stays close to 100%. That's the major benefit; where dust normally clogs the filter causing suction to fall off fast, the cyclone keeps most of the material separate and out of the airway.