Are two cyclone chambers required?

[steamngn]

Greetings all!
So I really wasnt sure how to word the subject.... but it kinda says it all :)
I am getting ready to build a pre-blower seperator and add a Wynn filter to an HF dust collector. Several builds I have seen remove the bag from the top of the HF cyclone, cap the top with plywood and then hang an open-bottom Wynn filter below with a collector bag or pail attached to the bottom of the filter. Question is, is that cyclone on top of the filter really neccessary? Any reason why the HF body shouldnt be used for the seperator and then just a simple box above the filter?

[alan m]

im not 100% sure what your asking but i think your asking if you can put the seperater part inside the ring of the dust colector
yes you can
personnaly i wouldnt . its too restrictive measurments wise. it could be done , and i think iv seen it done on here .

[retired2]

I'm not sure what you are trying to do either, but separators are called separators for a reason.  They remove solid waste and send it one direction and the exhaust air goes in the other.  The Wynn filter is your exhaust port and will work more efficiently and last longer between cleanings if the air stream is nearly free of solid wastes.

It sounds to me like your arrangement makes the Wynn filter the separator.  That is a really bad idea unless you want to spend all your time cleaning it.  My advice is stick with a conventional configurtion, i.e. Wynn filter above the separator and collection drum or bag below.     

[steamngn]

Retired2!
Have much of your posts and tests.... awesome!
Attached is a photo of somone's mod(not mine) using a dust deputy. Notice how the exhaust of the blower has an elbow going into the filter? I have seen this sort of mod where the original seperator ring is where that elbow is, and the top of the seperator is capped off with a piece of wood. If you look at the bottom of the filter there is a small dust bag to collect the knocked-down fines from the filter. It seems to me that a seperator ring at the top of the filter is needless and only serves to introduce more turbulence in the air going to the filter.
Thoughts?

[retired2]

The photo is a pretty conventional setup, waste goes down, scrubbed exhaust air goes up, and in this case around a few turns.  Nevertheless, the air has been scrubbed or separated before it hits the filter.

But I'm still confused about what you are describing.  Are you suggesting a separator in place of the Dust Deputy?  If so, you certainly don't want another at the entrance to the filter.  The loss in SP will kill you. 

If you mean, no separator before the blower, the something would be needed before the filter, but I don't know what that something would be so that it would not let a ton of dirt enter the filter.  The dirt is not going to magically fall down through the filter into a bag.  The fitter is exhausting all the blower air and that means all the dirt is going to get sucked (pushed) into the filter pleats.

[steamngn]

Sorry for the confusion all,
attached is a better picture of what I am asking about; notice how the original separator ring is now on top of the filter. Seems to me this not needed and would actually be counterproductive.
As someone coming from the world of metal :o I am looking at the stock separator ring and wondering if the built-in inefficiencies could be worked out to make the metal ring a suitable candidate to replace the perpetually-problematic plexi/lexan products everyone struggles with.
All of this is a lesson in study and understanding before I start to build my separator and in no way is meant to diminish or slight all the absolutely awesome work done by others to date. Trying to get the best understanding possible! ;D

[retired2]

Sorry for the confusion all,
attached is a better picture of what I am asking about; notice how the original separator ring is now on top of the filter. Seems to me this not needed and would actually be counterproductive.
As someone coming from the world of metal :o I am looking at the stock separator ring and wondering if the built-in inefficiencies could be worked out to make the metal ring a suitable candidate to replace the perpetually-problematic plexi/lexan products everyone struggles with.
All of this is a lesson in study and understanding before I start to build my separator and in no way is meant to diminish or slight all the absolutely awesome work done by others to date. Trying to get the best understanding possible! ;D

In you photo, if there is any separation occurring on the exhaust side of the blower, if is small, and it is a poor way of doing it because it exposes all the dirt to the filter.  I don't know why anyone would do that unless the headroom was a serious problem.  If you are going to use a second. Separator then vent the air up through the filter and let the waste swirl down into a bag.

Now back to your question is that second separator necessary?  I don't think so.  My dust collector is the Delta where the blower and separator cannot be used as two separate entities, or I might have gotten rid of the second when I added my top hat separator on the suction side of the blower.  I can run for months and only get a cup of waste from my plastic bag.  I don't know how much SP loss that second separation costs me vs just having the blower exhaust straight into a cartridge filter that is capped on one end.  I don't think it is very much, but I have no way to measure it.

Over the years I seem to recall quite a few variations on how the blower exhaust is handled, and there may have been some built exactly as you are proposing.  Frankly, it is how I would start building it.

[RobHannon]

I dont think the intention of that ring is to act as a seperator/cyclone so much as to be an easy way to mount the filter ont he exhuast side without having to fabricate anything. Many of the cartridge filters for dust collectors are sized to attach to those rings so it is pretty simple just to leave that part. You certainly do not need to do it that way. I have mine with an elbow coming off the exhaust straight into the filter.

[steamngn]

I agree Retired2; no sense in having that ring on the filter. I see several shortcomings in the stock separator ring that could be brought up to snuff with the plazma cutter and a few minutes work with polishing disc. I have already created a bellmouth on a piece of 6" S&D pipe to use for the outlet... not nearly as difficult as it may seem, and the heated plastic actually WANTS to make a transitional radius instead of a fixed radius... which nearly negated the vena contracta. For those who want to test a belled piece of pipe look to see if you have a local speed shop that can flow-test high-horsepower engines....
I will try my best to post pics and tutorials in the style of Retired2... tough act to follow! ;)

[Sthutch]

I dont think the intention of that ring is to act as a seperator/cyclone so much as to be an easy way to mount the filter ont he exhuast side without having to fabricate anything. Many of the cartridge filters for dust collectors are sized to attach to those rings so it is pretty simple just to leave that part. You certainly do not need to do it that way. I have mine with an elbow coming off the exhaust straight into the filter.

I agree with Rob, as I kept my ring simply to mount the filter.  Since height wasn't an issue, I kept it on top while utilizing the "separation/cyclone" within the ring to, hopefully, remove some of the fines that got by my Top Hat.

Sthutch 

[steamngn]

Sthutch,
I believe you are correct; the separator is being used as a handy way to mount the filter... however...
HOW-EV-ER.... this is introducing rotational airflow into the top of the filter, which then wants to be straightened out and then turned into the pleats of the filter. I'm not sure this is at all beneficial...  :o :o
Efficiency comes into play big time on the outlet side of things. Blowers (including exhaust fans for ventilation, which is what I am schooled in) are far better "pullers" than "pushers". much is being done to increase the efficiency on the "pulling" side while the "pushing" outlet side not so much.
4" pipe to a separator followed by 6" pipe separator to a blower with an 8" or 10" outlet with no bends... better to put an elbow at the top of the riser from the separator into the blower and have the blower exhaust in a straight line into the filter instead of the elbow on the outlet side.... of course space considerations come into play but you get the idea... I hope!  ;D
The potential exists to increase airflow while lowering motor load (amperage)... less turbulence in the exhaust stream = more efficient impeller load...  8)

[Sthutch]

Steamngn,

I think I get what you are saying, 4"ish into Top Hat, then 6" straight up from Top Hat into the blower impeller (which is mounted sideways), which then exhausts straight into filter housing.  However, since I am using the original bag housing it is causing the air to rotate before it is going into the filter, which if I understand you, is not desired.  So to remedy that issue, would adding a set of 4" to 6" "fins" made into a waffle like pattern on to of the cyclone housing be advantageous?  These would be similar to Retired2's air straighteners that he added to his Top Hat's outlet tube.

Sthutch

[retired2]

The greatest benefit of an air straightener comes when it is used to eliminate air rotation as it hits the impeller blades of the blower.  So, as I've said countless times, if your separator and blower are close-coupled, use an air straightener of some kind!  And that advice holds equally if your separator is a Dust Deputy.

On the outlet side I see no benefit to an air straightener, and it makes no difference if the filter is a pleated Wynn or a canvas bag.  On the outlet side you just want to keep the pipe big and avoid changes in direction.  If you must use a 90 degree ell to turn the exhaust down into a bag, this would be the place to invest in one the more expensive 5 segment long radius bends.  Those 1xD cheap ells you buy in the big box stores are so inefficient that fretting over other design details is mute.

[steamngn]

Retired2 you are correct on both counts. Even if your blower and separator are 6-8' apart straighteners will have a positive effect especially if your separator is reverse-rotation. There is no need for a straightener after the blower...
One thing that works well as as a straightener is honeycomb plastic grid. Can be purchased in sheets and cut easily. two pieces 6-8" apart in the riser oriented so the grids are NOT aligned (45 degrees to one another) works really well. Have never flow-tested a straw style but my guess is the results would be similar.
Most of the dust collector mods I've seen have the blower mounted such that the separator outlet is straight into the blower and then there is an ell on the outlet into the filter media. This should be reversed, with the separator outlet having an ell at the top and the blower oriented so the outlet is pointing straight down into the filter. Again, avoid any restrictions possible on the "pushing" side of the system.
And Retired2 those standard close ells are beyond awful! It is really surprising that they are used in any system at all. Remember that air behaves as a fluid in a closed system; the vena contracta phenomena happens with liquid too, and those ells cause it big-time!
When we flow-tested the 4" close-couple 90 from the box stores we found airflow rates restricted so much that the effective size of the pipe was more like 2 3/4" :o
If you have a commercial electrician in your area they will have heat blankets for bending 4-6" schedule 40 PVC; that is the heavy wall pipe. Those blankets work great on S&D (non foam core) pipe. Throw the guy a few $$ (I think I paid them $60 to bend two 90's) and you will have nice long radius smooth wall turns.... and the woodbutchers shall rejoice! ;D

[steamngn]

Good morning all!
Have a look at the attached picture; it is a profile schematic for a bellmouth intake design from Gordon P. Blair and W. Melvin Cahoon of Volvo-Penta Americas. These guys put huge amounts of effort into this research, and we've used this basic layout for all sorts of radius-ed intake inlets.
"De" is exhaust diameter, "Di" is inlet diameter, "L' is length and "Rc" is corner radius. Notice that "De" and "L" are equal; so optimally the length of the bellmouth from tip to concentric pipe is the same. "Di" is 2.13 times the exhaust diameter and is measured at the very end of the bellmouth before the end radius starts to turn back. The end radius "Rc" is .13 times the exhaust diameter. This end radius is important to smooth the inrush of air at "Di".
SO... if we are to use 6" pipe for our project, optimally the inlet bell would be 12 3/4" diameter and the end radius would be 3/4".
Now obviously these optimal dimensions will be constrained by other factors like available space etc. but hopefully this gives everyone some guidance!