Another Dust Collection Quandary For the Experts

[Ed in Tampa]

Since the experts are involved here can someone explain to me why most shop vacs filter the air before it goes through the fan but most dust collectors run the debris ladened air through the fan. Why?
Is it ease of design and build or is there a real reason the debris ladened air must pass through the fan on dust collectors?

Thanks I advance!

[jsburger]

Since the experts are involved here can someone explain to me why most shop vacs filter the air before it goes through the fan but most dust collectors run the debris ladened air through the fan. Why?
Is it ease of design and build or is there a real reason the debris ladened air must pass through the fan on dust collectors?

Thanks I advance!

That is the beauty of the cyclone dust collector. Almost all of the dust is seperated out before the air goes through the impeller and out the filters.

This would be my guess to your question. Dust collectors and vacuums are really two different things.

Shop vacs are high static pressure and lower flow.

Dust collectors are low static pressure and high flow.

Air flow (CFM) is one of the important numbers for a dust collector. Shop vac CFM in most cases is in the low 3 digit range. Dust collector CFM is in the 4 digit (well, except for the SS DC) and up range. To get a lot of air flow you need a lot of filter area and a big fan/blower.

To build a dust collector in the same style as a shop vac it would have to be huge to fit a filter large enough to support the CFM of even the most modest dust collector. Then taking it apart to empty would be a major undertaking.

As an example of this look at the SS DC. Compare the size of the standard 7 micron filter bag and the 1 micron bag. The 1 micron bag is around three times or more larger. Since it is finer it needs more area so the DC can maintain the rated CFM.

So my conclusion, right or wrong, is that the way non cyclone dust collectors are made is the only practical way to do it. Lots of companies make them and they are all pretty much the same.

The Oneida Dust Deputy added in front of a conventional bag dust collector would solve the problem of most debris going through the impeller.

As a testament to the efficiency of a cyclone see the pictures of my Clearvue cyclone. The first pictuer shows the unit just after I installed it. The next two pictures show the cleanout at the bottom of the filters. Those two pictures were taken today 6 1/2+ years of use and it has never been cleaned. Just over 1/8" of dust.

[JPG]

Shop vacs have small impellers with multiple direction changes and are intended to pick up small dust particles.

A 'dust collecter' has impellers with large widely spaced blades that allow larger chip sized particles to pass through.

[GoNavy]

I don't know Mark, but both of those units look exactly like my HF unit, spec are similar, they look like they are just painted a different color. The HF unit is half the price, with the the money you save you can do the Wynn Environmental canister upgrade and end up with a much better DC..been using the HF DC with the upgrade for a few years now and pretty happy with it...

https://www.harborfreight.com/70-gal-2- ... 61790.html


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[Ed in Tampa]

From JSBurgers picture it is possible to build a dust collector that filters out most dust before it passes through the fan blades. Why doesn't all dust collectors do that? I know with my DC 3300 I am always hearing things hitting the fan blades. Paper that gets sucked up is the worst as it usually gets stuck on the fan blade and I have to remove the dust bonnet to clear it.

It seems the present construction of most dust collectors is quick and dirty but the manufacture still sells them at premium prices. $500 for something that is little more than a stand, 1-11/2 horse motor, a fan blade and two bags??? Move up to a 2 horse unit and the price jumps to around a thousand. Talk about getting what you paid for.

I would never buy a another dust collector that did not have a cyclone separator before the fan.
And I would think it should cost about the same price of a non cyclone machine.

[mbcabinetmaker]

I don't know Mark, but both of those units look exactly like my HF unit, spec are similar, they look like they are just painted a different color. The HF unit is half the price, with the the money you save you can do the Wynn Environmental canister upgrade and end up with a much better DC..been using the HF DC with the upgrade for a few years now and pretty happy with it...

https://www.harborfreight.com/70-gal-2- ... 61790.html


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I had one of the HF in another shop several years ago but it had a plastic impeller and didn't last very long. Maybe they are better now. Anyway Baileigh wanted $200.00 shipping on their unit so for me that was a deal breaker. In the end I decided to buy another Festool CT26. I just like the convenience and smaller footprint and I wont have to move anything around to make it work. Im also working on a way to empty the Festool bags into the large JDS unit so that I can get more miles out of my bags. I may look at adding the Dust Deputy to at least one of the CT's depending on how that goes. Thanks for the mention of Wynn Environmental I looked them up and they are a good source of filters for the future. https://wynnenv.com/woodworking-filters/

[GoNavy]

The HF DC have steel propeller these days. I have it in a fixed position of my shop with 4" PVC sewer line run to each drop to the various tools in the shop, blast gates at each tool and flex to the tool itself with the Long Ranger remote turn on (open blast gate to turn on DC, close gate to turn off) works very well. The Wynn filter are much much better, actual improves performance. I must say jle suggestion of the Laguna unit is impressive, if I ever upgrade, I believe that would be a good unit, but for now the HF does well enough.

edit: Was going to find the link to the 110 version of the long ranger multigate switch system, but seems to be hard to find, they seemed to only selling the 220v version these days, it's to bad really nice system

[masonsailor2]

The HF version I have has a metal impeller. I got it off CL for $75 years ago. I use the standard filter bag it came with because mine is outside the shop so I don't care about the particulate. The thing is very reliable. I use the 110 V remote that Rockler and Woodworkers Supply both sell. The nice part is that you can use the heavy duty black trash bags on them which are cheap. I have a separator which is a metal trash can which saves emptying the bag so often. It sits out doors unprotected and seems to be doing fine. I expected the filter bag to deteriorate due to rain and sun in Southern CA and now Las Vegas but it seems to be holding up.
Paul

[bobgroh]

No solutions here but some thoughts and opinions. In any event, I recommend a two stage filter setup - with a cyclone on the front end, then the fan and then a high filtration bag on the fan outlet. From what I have read, a cyclone is superior to the 'trash can' collector. The overall size (CFM) of your system will be dictated by your shop - size of tools, whether a permanent piped system or just a roll around, etc. You want to keep the dust velocity up past 4,000 fpm (to keep the dust in suspension) - that is easier to do with small pipes (e.g. 2-1/2") and harder to do with larger. Laguna has some nice systems and so does Oneida Air although they are not inexpensive ($800 to $1200? for the sizes we are talking here). If you buy a system such as the HF units and want to add to a cyclone or trash can collector (TCC) on the front end, remember you will lose a bunch of CFM. And you do have to match the cyclone/TCC to the system - cyclones do have a 'sweet' spot in the CFM rating (which is why a Dust Deputy does NOT work well on a DC-3300!).

[JPG]

. . . (which is why a Dust Deputy does NOT work well on a DC-3300!).

Maybe not 'well', but quite good!(no trapped debris in the hose(s) with heavy planing etc.).