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

[mike52732]

retired2 Thank you for posting the sketchup file.  That will be very useful to me.  I am getting ready to build a new top-hat for my up and coming Gatton-CNC and I like some of the mods you have made.  So far my top-hats have all had metal in place of the Plexiglas and small 5 gal. buckets.  I like the idea of being able to see whats going on.

Mike

[benji791]

Hello,

I'm planning a separator for my 1-1/2HP dust extractor. Unfortunately mine is only equipped with a 4" outlet. So any CFM that I can avoid to lose with the separator is important. With its 11" turbine, it is rated at 700cfm and 40m/s
I plan to use the same design with rectangular inlet and bellmouth outlet + air straightener. That's why I did not create a new topic. If you think should create a new topic, feel free to let me know.

I also have concerns in footprint for the separator. The height is not such a problem (Probably I will extend it to a 2H design).
I found a those nice barrels that are only 15-3/4" dia with 12-1/2" opening. They are quite beefy with nice handles and locking lid. Note, that I don't plan to use the lid on the picture to make the top hat. It would be only used for transport when needed put it in the car to go to the waste collection center.

The 20" garbage cans that I can find are not so robust or really expensive.

I undertood that the wider the separator, the less SP drop I will get. I also undertood that with 4" inlet and outlet there is a big risk of bypass. But what if my round to rectangular transition is quite long with tall but thin rectangular section (let say 5" x 2-1/2"). I would make the transition part 20" long.
As a comparison I see that the CV1800 cyclone from clearvuecyclones  with its 6" inlet and outlet is 18" diameter but it has a long round to rectangular transition (quite thin but tall at the end rectangular section). Keeping those proportions would mean 12" diameter for 4" outlet and inlet. But maybe in this case, it would be safer to skip the bellmouth and just keep the air straightener.

Are there any things that I missed? Is the top hat so much different from the upper part of a cyclone? Or do you think it could work.

Benjamin.

[kmerkle]

Where did you get the bellmouth?

[Alan H]

Where did you get the bellmouth?

I'll second that request.

[retired2]

Where did you get the bellmouth?

I'll second that request.

I got my bellmouth from a local spiral wound pipe fabricator.  They also fabricated the custom dust hoods for my thickness planer, jointer, and the round-to-rectangular transition piece for my separator. 

Bellmouths are available from a number of online sources, but  off the top of my head I'm not certain which ones.  Start with PSI (Penn State Industries) or Oneida Air.

[RobHannon]

I got a 6" bellmouth along with other fittings from here:

http://warehousecatalog.rlcraigco.com/viewitems/ductwork-take-off-fittings/spun-bellmouth-take-off

Prices were decent and they were pretty easy to work with. Selection is somewhat limited however and 6" is the smallest bellmouth they list.

[OCJoeR]

I've been reading all the posts on here since I'm trying to find some answers to questions regarding building either a top hat or internal baffle. Of course I did this after starting an internal system. I think I'm going to forgo the space issue I have and go with the top hat build. I've noticed much discussion regarding the use of one form or another of plastic for the side of the unit. There appears to be issues with it cracking in some instances. Is there some reason galvanized steel can't be used? It obviously isn't going to crack, even with holes drilled in it.

thanks,
Joe

[retired2]

I've been reading all the posts on here since I'm trying to find some answers to questions regarding building either a top hat or internal baffle. Of course I did this after starting an internal system. I think I'm going to forgo the space issue I have and go with the top hat build. I've noticed much discussion regarding the use of one form or another of plastic for the side of the unit. There appears to be issues with it cracking in some instances. Is there some reason galvanized steel can't be used? It obviously isn't going to crack, even with holes drilled in it.

thanks,
Joe

The reason is you can't see through steel!😄  Is it critical?  No, but when a plug develops, or you overfill your drum, it's nice to be able to see at a glance if your separator is jammed ir not.  And when you clear the jam it is nice to know at a glance that you've got it all.

I glance at mine quite often, because the way mine us buttoned up it is one helluva mess to clean out.  I've done it several times with wet shavings, so I'm paranoid. 

The guys who have used Lexan don't seem to have the problems with cracking the way plexiglass users do.  However, Lexan isn't nearly as cheap.  And many places will not cut sheets to smaller sizes. Forget the big box stores, go to a place that sells only glass, shower doors, and mirrors.  Mine shop will cut anything I want and he charges only for what I take, and very fair prices.

[OCJoeR]

Hi Retired,

If I neglected to say it before, great thread! And great photos.

I knew it had to have something to do with watching saw dust and chips, lol. I guess I'll go with it. I'm wondering if heating it as the holes are drilled and while inserting the screws through it will help with the cracking issue. I'll cut a strip and give it a try and report back.

Joe

[retired2]

Hi Retired,

If I neglected to say it before, great thread! And great photos.

I knew it had to have something to do with watching saw dust and chips, lol. I guess I'll go with it. I'm wondering if heating it as the holes are drilled and while inserting the screws through it will help with the cracking issue. I'll cut a strip and give it a try and report back.

Joe

If you are using plexiglass, I don't think heating is going to help.  It is worth noting that hearing does make it very easy to bend the plastic to to ID of the separator.  My wife's hair dryer worked fine.  The plexiglass does have a memory, so when you remove the heat it quickly stiffens and wants to open.

Somewhere, if you search, I posted a video with a concept for attaching and sealing the plexiglass without screws.  I had already finished my build or I would have tried the concept.  The video shows it has great promise.  If I can find the link I'll repost.

[retired2]

Hi Retired,

If I neglected to say it before, great thread! And great photos.

I knew it had to have something to do with watching saw dust and chips, lol. I guess I'll go with it. I'm wondering if heating it as the holes are drilled and while inserting the screws through it will help with the cracking issue. I'll cut a strip and give it a try and report back.

Joe

If you are using plexiglass, I don't think heating is going to help.  It is worth noting that hearing does make it very easy to bend the plastic to to ID of the separator.  My wife's hair dryer worked fine.  The plexiglass does have a memory, so when you remove the heat it quickly stiffens and wants to open.

Somewhere, if you search, I posted a video with a concept for attaching and sealing the plexiglass without screws.  I had already finished my build or I would have tried the concept.  The video shows it has great promise.  If I can find the link I'll repost.

Here you go, a challenge for you:
http://www.jpthien.com/smf/index.php?topic=573.msg3105#msg3105

[retired2]

I've been meaning to do a comparison between a cloth filter bag and a Wynn 35A Nano cartridge filter for some time.  I finally got around to it recently - the test data is posted in the table below.  Some of the data is repeated from a much earlier post (#99) for your convenience.  This will allow you to easily compare air flow between 1) no separator, 2) no filter, 3) a 1.0 micron cloth filter, and 4) a Wynn 0.5 micron nano filter.  The bellmouth and air straightener were installed in all tests except where the separator was removed.

Air flow measurements were taken exactly as before, i.e. several readings were taken along the edge of the inlet pipe and several were taken at the center.  All readings were then averaged to obtain the final number.  CFM's were calculated from the FPM readings. 

The cloth filter bag is not new, but before the test it was turned inside out and thoroughly vacuumed.  The Wynn filter has never been used.  I was surprised the air flow readings were so similar for the cloth filter and the nano filter.  It would be interesting to see how they compared after some period of use.  However, that test would be a lot of work because it would require exposing both filters to the same kind of waste for the same period of time in order for the test to be valid.

[JeffQ]

Huh! I never would have expected the values between the new Wynn filter, Seasoned bag and No filter/bag to be so close... or for that matter for the separator to cause so much of a hit in airflow.

[B2Pi]

Has anyone seen data for adjusting the height of the bottom of the Bellmouth input relative to the height of the inlet? (I'm assuming a now-standard (I think) 2H system)

[retired2]

In reply #99 of this thread, I provide data for three different positions of the outlet.  There may be other comments buried elsewhere in this thread.  However, my build is not a 2H separator, so I don't know what conclusions you can draw from my data.  I think quite a few people have built 2H separators, but I'm not sure it is the standard, and there is no hard data to prove it is any better.