5", Rectangular Inlet, Bellmouth Outlet with Air Straightener, Top Hat Separator

[dabullseye]

Maybe u could some compression springs in the corners to carry some of the load of a full can and help in when the cam comes over center.

[retired2]

Maybe u could some compression springs in the corners to carry some of the load of a full can and help in when the cam comes over center.

That could be a little tricky.  I only have 1" of travel.  Of that, 3/8" is to engage the drum groove and 1/8" is for overtravel.  That means in the full retracted position, the top of the drum clears the bottom of the separator by just 1/2".  If the compression springs kept the table from fully retracting, I might not be able to get the drum out.  That's not likely to be a problem with a full drum, but if I need to get it out with a partial load, or no load at all, the springs could keep the platform raised.

However, your idea might be a good one for an entirely new design.  I'm thinking four strong springs could provide the lift power, and the separator could then be suspended in a fixed position with no springs.  To empty the drum there would have to be some kind of crank, or clamping mechanism, to compress the springs, and then release them to reseal the emptied drum.

[retired2]

AIR STRAIGHTENER - WHAT NOW?

In an earlier post I discussed the increased noise I am getting since I installed my separator.  It is very annoying, so I began investigating the problem further and discovered that I mis-diagnosed the source.  It is not the baffle or the plastic drum.  When I put my hand around the neck of the separator exit pipe there was almost no vibration, but when I grabbed the neck of the DC inlet pipe, the vibration was very noticable.  However, it is not a mechanical vibration, and it stops when the separator is disconnected.  I became convinced that the vibration is from air turbulance resulting from my counter-rotation separator.

So, to test this theory, this evening I tried "plauale's" suggestion and stuffed my separator outlet pipe full of "straws" to straighten the air.  Hope you're following this thread plauale!  The results have really left me scratching my head. 

First, here's a photo of the modification.  I cut two light-walled plastic shipping tubes into 8" lengths.  Then I stuffed as many as I could into the 5" separator outlet pipe and soaked all the contact lines with crazy glue.  They aren't going anywhere unless they shatter, and then the fan impeller will eat them like rice crispies.




Here's what happened when I fired it up,

1) Big drop in noise level, 4-5 db.   May not sound like much, but that's a huge difference in comfort level.
2) Amp readings dropped a little.  That's not good, but I need to test this a little more.
3) Waste stream inside the separator now oscillates in a flat sign wave pattern, rather than continuously spiraling downward.
4) Waste stays suspended a little longer, but still separates.
5) A very small amount of by-pass occurs when hit with a heavy waste stream.   I dumped more than 1/2 of a garbage bag of shavings in front of my floor sweep and then shoved it in.  It would take three thickness planers to generate that much shaving dirt, but the separator still worked.


At this point I'm not sure what I want to do.  I could do more testing - yuk!  I could build a mirror image separator - double yuk!  Or, I could leave it as is - maybe!

Update:

Here are two short video's showing the change in separator behavior with the air straightener added.  The first video shows the amount of waste used in the test and the rate at which I was feeding it.  The second video shows the change in the vortex.  Compare this video to the one I posted in Reply#40 (no air straightener).

It would appear in the earlier video the waste stream is tilted down, while with the air straightener added it is tilted up.  In hindsight, I should have looked at the waste stream from the opposite side.  It is quite possible the waste stream always flows in a tilted plane, and all the air straightener did was rotate where that low point occurs.  Can anyone verify this?  I'd do it myself, but at this point removing the air straightner is quite a bit of work. 

The video below with the air straightener makes you think the separator can't possible be working, but within a second or two of stopping the waste feed, the separator chamber is empty and the plastic bag shows only a few straggler chips have by-passed the separation.

So for the time being, I am leaving the air straightener in place.  I can see no real loss of performance, and it is sooo... much quieter.  The low frequency rumble from turbulence is gone.


https://www.dropbox.com/s/xngk0vs33gctl0g/AirStraightener01.MPG?dl=0

https://www.dropbox.com/s/l7t2ntiqd2jg79f/AirStraightener02.MPG?dl=0

[retired2]

UPDATES:

Added final photos of the lift table assembly to Post #85, and added videos of the separator performance with the air straightener installed.  Those videos are in Post #92 above.

[Don_Z]

Very nice work. I want to see it suck on some MDF though so I can compare it to how mine works.

[retired2]

Very nice work. I want to see it suck on some MDF though so I can compare it to how mine works.

Ship a box full to me.  I'm trying to avoid making any MDF fines!

By the way, I thought you were working on a kitchen project.  How do you have so much time for these separator fun and games?

[Don_Z]

Because I hate watching lacquer dry...

[plauale]

I am following Retired2, and I think that tubing you used is more appropriate than straws. However this IS quite a head scratcher, the only question i had after watching the videos was the bell-mouth outlet seemed to be a bit deeper in the separator on the later video. Don't know if it makes much of a difference, I assume you played around with that since you have little markings on the side... And then again, as you say, there is little loss in performance and lower noise: so you could just call it a success. Plus the whole setup looks really nice!

[retired2]

However this IS quite a head scratcher, the only question i had after watching the videos was the bell-mouth outlet seemed to be a bit deeper in the separator on the later video.

You're really observant, plauale - I didn't think anyone would spot that difference.  After I shot the second video, I discovered the outlet pipe had slipped down without my knowledge.  I think it slipped down when I pushed the "straw" bundle in place.  I've since pulled it back up and reapplied fresh rope caulk.  A quick check didn't reveal much difference in the performance of the waste stream.  However, I didn't spend much time looking.  I'm waiting for the anemometer I ordered to arrive, then I hope to be able to provide more definitive answers.

[retired2]

Well, I received my new anemometer on Friday, so today I spent a really long day doing more testing.  It was a long day because I had to start by removing my separator suspension system so that I could make all the setup changes I wanted to measure.  It didn?t help that I have one helluva cold, or whatever it is.

For those of you that like a lot of numbers you will have to wait until tomorrow.  I need some time to format the data.  I have anemometer, ammeter, and sound meter readings for a variety of setups.

For those of you who don?t like numbers, here is a brief summary of the findings:

  1) The bellmouth outlet works better than a straight pipe (Straight pipe w/air straightener matches or exceeds bellmouth w/o air straightener).
  2) No performance penalty for the air straightener.  It actually improves the performance of  both the bellmouth and the straight pipe. 
  3) The depth of the straight outlet pipe makes no difference in velocity readings.
  4) The depth of the bellmouth outlet pipe shows very slightly higher air speeds when it is set high than when it is set low.
  5) Noise levels are lower with the air straightener installed (less turbulence).
  6) Meter readings are more stable with air straightener installed (less turbulence).
  7) ?Plauale? is definitely not crazy!  He's the one that suggested I install straws in my outlet pipe.

It is safe to say from the above summary and the data that follows, every close-coupled (to DC) separator should have an air straightener installed in the outlet pipe - regardless of separator rotation.

The $64K question is how would these test results change if my separator were not counter-flow?  We?ll never know for sure because I don?t intend to build another one and go through all these tests again!  But if I had to guess, I would say a same-direction separator would be better for those setups that do not include an air straightener.  With the straightener, I would expect them to be the same.   

Here?s some photos of my test setup.  The first photo shows the quick and dirty mod I made to my floor sweep.  This is the inlet pipe that was used for all anemometer readings.  The second and third photo give you some idea of the distance to the DC.









NEW TEST DATA

O.K.  Here's the test data I promised.  The test with the filter bag removed was performed to get some idea how a Wynn Filter might improve test results.  It's not a perfect test, but it provides a good approximation.  (See additional comments below test data)


I think it is worth making a few comments on the data above.

1)  FPM data is an average of two readings, one at the edge of the pipe and the other in the middle of the pipe.

2)  CFM are calculated numbers.  They are not measured, and they are calculated on the basis of a 5" pipe which is what my system is.

3)  Don't put too much faith in the absolute numbers - they fluctuate far too much.  It is the relative differences that should be noted.

4)  It is impossible to get a single test number that is 100% accurate and repeatable.  Testing a DC system is not like checking the air in your tires where conditions are static and a good gauge will give you the same reading every time.  With dynamic conditions like these tests, the numbers will be different everytime, but the relative relationships should remain pretty much the same.

5)  Aside from the fluctuations that result from turbulance throughout the system, I've learned that at least two other things affect the numbers.  The first is the temperature of the DC motor.  A cold motor produces better numbers than one that has been running tests for an hour or more.  I've also discovered that my Long Ranger relay adversely affects the performance.  The penalty is extremely small, and would probably never show up in actual performance, but it can be seen very consistently with the test instruments.  I'm not sure why this is happening because I checked the voltage, and the relay is passing full line voltage.  Any electricians want to comment on this?

6) Air straighteners improve the performance of both the straight and bellmouth pipe by about 40-50 CFM - not huge, but not bad since it also improves noise levels as well.  If I weren't burnt out, I would run a few tests on air straighteners.  First, what shape works best?  Would four longitudinal vanes produce the same results as a bunch of plastic tubes?  How long(or short) should the straightener be?  Where should it be positioned?  My testing was done with the straightener placed nearly flush with the entrance to the exit pipe.  Maybe it would be better if it were closer to the DC than the separator?  Anyone want to take on these tests?  I'm done.

7)  You can see from this data that under the best conditions my separator imposes a performance penalty of about 300 CFM or 2000 FPM.  That is substantial, and it is the difference between maintaining or not, the minimum recommended speed for conveying woodworking waste.  I see no evidence that waste is settling out in my headers, but I can see small amounts of waste on machine beds that weren't there before.   The other machines I would like to add to my DC system, such as a miter saw and radial arm saw, will need lots of air to be effective.  When that time comes, I will probably be faced with a really tough decision.


If I make any any further changes to this post, other than the missing data in the table, I will highlight them in color.


Update:

Well, the test data with the filter bag removed was very disappointing.  As you can see from the numbers, there is really no difference whether the bag is removed or not.  I can think of two reasons for this.  First, I turned my filter bag inside out and vacummed it before I started testing.  So, it is essentially a "green" bag.  Second, the CFM's in all these tests are not terribly high, so the filter bag is not being inflated very firmly.

As my filter bag develops more cake, I would expect to see test results that make a Wynn Filter look more attractive, but for right now I don't see any reason to rush out and buy one.

[retired2]

Well, are your eyes glazed over yet?  If not, I want to share another discovery I've just made while checking my test data for consistency.

If all things are equal (and that is the key), ampere readings move in sync with the volume of air being moved, i.e. if ampere readings go up, more air is being moved, and if they go down, less air is being moved.  So, when I noticed a comparison number in my data that was contrary to this simple rule, I dismissed it as an aberation resulting from the fluctuating readings produced by a DC system.

What I've since discovered is that it isn't an aberation at all, but rather it is part of a consistent pattern that shows the addition of an air straightener allows the fan to move more air with fewer amperes.  If you go back to my test data and compare the numbers for a given test without the air straightener to the same test with the air straightener, you will see that in every case the fan is moving more air with fewer amps when the air straightener is installed.  So, if your DC is marginally powered for your system, as mine is, milking every last ounce of performance out of the fan is important.

Sometime earlier I posted this paragraph from a Cincinnati Fan Engineering manual regarding duct inlet spin.  The above discussion and test data seems to validate Cincinnati's statements.  Again, you should keep in mind, all my testing was done with the separator close-coupled to the DC.  So, I don't know how relevant any of this is when there is several feet of pipe, hose, or elbows between the two.   

Duct Inlet Spin
"A major cause of reduced fan performance is an inlet duct connection that produces a spin or pre-rotation of the air entering the fan inlet.  Inlet spin in the same direction of the fan wheel will reduce air volume and pressure ratings.  Inlet spin in the opposite direction of the fan rotation will substantially increase the motor horsepower requirements.  An ideal inlet condition is one which allows the air to enter the fan axially and evenly without spin in either direction."

[retired2]

Hey Don_Z, you've been awfully quiet recently, have you od'd on laquer thinner? :) 

You need to get that kitchen project finished so you can get back to more important things like helping out with this separator testing!

On a more serious note, I was wondering if you have done any testing to determine whether the depth of the outlet pipe improves separation with MDF fines? 

I don't have any MDF waste to test right now, so all I have to go on is my test data which shows a slight improvement in air flow when the outlet is deeper in the chamber, i.e. closer to the baffle.  But with the pine planer shavings I have been using for testing I really can't see much, if any, difference in separation at the various positions.

Hey, all you lurkers, what's your experience?  This thread has over 2600 views, surely some one out there has something worth sharing.  Help out here - post something!

[Don_Z]

Actually, I have noticed that since attaching the bellmouth and dropping it down that I have zero bypass with mdf or  any unlucky small kittens that happen to get sucked through. I have been reading your test results and have been waiting and considering if and how adding "air straighteners" would be adding to my system. I will say that I am considering buying a new 3 hp penn state or grizzly to replace the HF model I started this project out with. Need to get the uppers hung before the wife will let me do much of anything though :(

[retired2]

I will say that I am considering buying a new 3 hp penn state or grizzly to replace the HF model I started this project out with. Need to get the uppers hung before the wife will let me do much of anything though :(

I suppose we could have quite an active thread on just Dust Collectors, but if money were no object, and of couse it always is, the one I would buy is the Oneida Smart Collector.  It's a portable cyclone that somehow adjusts the sp to compensate for hose and port sizes.  I think it can develop a max. of 20" sp.  That's not exactly a shop vac, but it is considerably more sp than any DC I know of.  And of couse, it is capable of moving plenty of CFM when it is needed, and it's quiet. 

[Don_Z]

But that would take away the fun of building the separator then. Nice machine specs, but looks like a dated piece of crap. You would think for that price they would update the looks. I like the looks of the new Laguna models, but they perform terribly.