Every day in Every way bagged is better.
James Dyson freely admits his inspiration for the dirt separating cyclones came from observing a huge 2 story high industial cone shaped workshop dust extraction unit in operation. The debris swirls around the inside of the cone and falls by gravity through the pointy end into a cloth bag larger than a man. You'll find this type of vacuum unit in most industrial workshops - we have several at work for the Carpentry shop and another for fumes in the Welding shop. His goal was to scale it down to portable domestic size. Can't be done and also satisfy all the other requirements of a vacuum unit for daily or weekly cleaning but you can dress it up in a pretty complicated flashy looking high maintenance package.
The principal at work here - bagless debris collection - had already been figured out by Filter Queen, Nilfisk, Rainbow and others. You need a cylindrical tub of large diameter with a central fan or radial tangent inlet to stir up a swirling tornado maelstrom to fling the dirt solids to the sides and a correspondingly large area of last stage filter medium to catch the fine powder exiting the upper chamber. If one is really concerned about the fine powder exiting such a vacuum design you could place a HEPA medium inside a canister that attaches to the exhaust port. FQ calls theirs a De-Mother and Fairfax has the Filterizor. Just replace that foam insert with a circle of paper dust bag or HEPA medium. But you won't see much powder collect there. Barring a burst bag or leaking around the edge of the chamber sealing gasket, how long does it take for the round yellow motor filter disk to clog up in a Eureka/Kenmore 'canned ham' clamshell canister or the motor filter of a Compact or Constellation? It doesn't. Of course, these are vacuums with bags and we're discussing bagless designs...
I'm sure his prototypes passed air like nobody's business but in his eccentric quest to prove he could do it he had to add multiple stage filters and a twisting internal (dust snagging) air path so the exhaust airstream appears to be dust-free. There's more than a few of us here who have dismantled bagless cyclonic vacuums and seen the cholesterol-like clogging and narrowing of the air path. Other than the hose, direct path bagged vacuums have no such buildup and even then it's usually caused by vacuuming moist matter occasionally. Hoses can be soaked in a tub of water and have a bristled bottle brush run down the length to keep keep them fairly clean and certainly this is how to renew a tired old hose during restoration.
Bowing to the inevitability of Dyson's 'hammer-to-the-forehead' marketing and financial success other manufactures followed suit and HEPA came along as yet one more filter medium to capture the nano particles. Medical and Industrial HEPA & electrostatic filters have a considerably larger surface area than can possibly contribute effectively in a small home unit. What's the point? Sucking up the very building block essence of the physical world? As we all know, these filters must be cleaned out after every use, washed if permanent...and replaced if disposable or they dislplay a dramatic loss of suction, which Dyson uses as a slogan but neatly sidesteps by playing it down and every Dyson Owners Manual clearly states that washable filters must be cleaned regularly, without committing to how often. Dysons and competing bagless vacuums lose suction noticeably during one cleaning session. There is no way around this - a bagless vacuum must have it's filters washed and thoroughly dried after every use or your HEPA will become as impermeable as a sheet of Kraft paper. And I mean 'bone dry' over a hot air register for example or your fine organic matter powder will cake up around the filter pores leading to utter loss of suction.
It takes longer to clean up and prepare a bagless vac after a one time use for its next using than to do the actual vacuuming chore, taking into account washing and drying the filters, shaking off the cones, emptying the dust cup and wiping down the plastic exterior.
Loss of suction is not something you're going to face with a true cyclonic bagless tub like an FQ (or ShopVac or the older style GE & Eureka Roto-matic open paperbag-lined central swiveltop tub vacs). In an FQ The filter cone supports the 2 square foot paper filter medium in a horizontal plane. Gravity and the jostling of the machine on its way back to the storage closet is enough to shake the powder off the filter into the tub. Have you ever seen a dusty residue around the top cap of a paper coned Filter Queen? Even after weeks or months of regular use?
Set a Filter Queen/ShopVac/Nilfisk beside a modern plastic Bagless Cyclonic...with all filters removed...and compare how much debris passes through and exits the exhaust end - you'd be so horrified you'd never go bagless again.
Filter Queen has never felt compelled to add a paper liner or dust collection bag to their product. Lewyt 55s and Fairfaxs that did & do have simply added a large powder filtration area to the airsteam and provided a convenient way to dispose of the collected dirt without spillage. Empty or full to capacity, I get the same suction readings from a tub vac.
With bagged vacuum of whatever design outfitted with multi-layer bags these questions never come up - they too, do not lose appreciable suction in use over the long term.
my 17 cents worth.
Dave
