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

[dabullseye]

i got mine thru penstate ind. its spun steel. i took my off within the first week because it didnt fit my pipes and i had to turn an adapter out of wood. since im no rocket scientist and dont have any real fancy equipment to test my setup except what i can see with my eyeballs i could see more bypass from my lathe sanding and my drum sander. and as i have said before in 3yrs i have less than a quart of fine dust in my bag on the bottom of the 50-850 ring. also my center outlet pipe does not extend into the chamber as far as what everybody else does. 
od= 9.5"      (9 1/2" )
id=  4.75"      (4 3/4")
ht=  2.625"    (2 5/8")

[JonWho?]

Thank you. My appologies if you've posted the link several times.

I was curious about the increased waste bypass associated with the 6" bellmouth that R2 mentioned earlier

The 6" bellmouth I'm using has a 1 3/16" radius & the overall diameter is smaller than R2's 5" bellmouth. The smaller radius will cause more turbulence than the 2" radius in the 5".  It's still gonna be better than a straight pipe.
I could just make my own by stacking layers of scrap Type 1 Pvc & use my 1.5" Roundover for the flare. Then I can machine a Roundover on the outside & chamfer the back of the flare.

Of course if I go that route I might as well make one for each machine too. I sure know how to create a lot of work for myself! I don't believe there's an end to what can be tried & tested.

On a side note. Retired2, Crazy that bellmouth weighs 1.5 lbs!

[retired2]

JonWho,

If you do some searching on the internet you will find that a true bellmouth is the most efficent entry port, and a straight pipe is the worst.  However, what you will also find is that many variations produce a good deal of the benefit of a bellmouth.  Even a flat flange on the end of a straight pipe is more efficient than straight pipe.

Now all this efficiency stuff has to do with airflow, it has nothing to do with waste separation.  And it now appears there is some evidence suggesting that a large bellmouth flange in a separation chamber that is not sufficiently large will suck in more fine waste than a straight pipe.  So, given the variety of pipe endings that come close to the efficiency of a bellmouth, it is possible that the best solution is a trimmed down bellmouth flange, or even a fabricated radiused tail piece fitted onto the outlet pipe.  In fact, the bellmouth you say you have, might be the ideal fitting!

[Carl]

Retired2 - I have been following yours and many others designs and am about to embark on some variation of the many shown but will start using my DC ring with a baffle.  I wanted to start with some baseline measurements.  You mentioned earlier in this tread that you measured the FPM at the center and edge of the pipe.  Is there any reason for the two and is there anything special about how to measure the edge flow (besides bringing the edge of the meter to the edge of the pipe - on a 5" pipe that is only 1.5-2" move)

This forum is great - I am glad to see there other over analyzers like me on this site (-:

Thanks,

Carl

[Carl]

Well I have answered my own question.  I started taking some baseline measurements of my Jet DC1100 (original) with various piping and different turn combinations.  4,5 and 6 inch duct and PVC (4") along with short and long radius turns. I will post data soon but preliminary test supports significant efficiency in larger pipes and turns.  I know I can't support 6", but 5" shows a big improvement over 4" and larger turn 90s show better performance as well. 

This has all been stated before but I did some preliminary theoretical calculations based on my small shop and runs and didn't think there would be much difference....there is!!!

The center/edge FPM measurement was interesting as the flow is reduced on the edge (as you would expect) more than I thought.

I will post my data and my build progress in another thread in the week or so.

Carl

[phil (admin)]

The center/edge FPM measurement was interesting as the flow is reduced on the edge (as you would expect) more than I thought.

Carl

I've often wondered if I could use that to make an in-pipe separator.  I've watched my clear plastic pipe while dust is flowing and I can see the dust hugging those walls.

[dabullseye]

phil how much does static play in that dust hugging the sides of tube

[JonWho?]

JonWho,

If you do some searching on the internet you will find that a true bellmouth is the most efficent entry port, and a straight pipe is the worst.  However, what you will also find is that many variations produce a good deal of the benefit of a bellmouth.  Even a flat flange on the end of a straight pipe is more efficient than straight pipe.

Now all this efficiency stuff has to do with airflow, it has nothing to do with waste separation.  And it now appears there is some evidence suggesting that a large bellmouth flange in a separation chamber that is not sufficiently large will suck in more fine waste than a straight pipe.  So, given the variety of pipe endings that come close to the efficiency of a bellmouth, it is possible that the best solution is a trimmed down bellmouth flange, or even a fabricated radiused tail piece fitted onto the outlet pipe.  In fact, the bellmouth you say you have, might be the ideal fitting!

R2, Thank you for the response. We're on the same page. I'm no engineer but I know a little about bellmouths. Maybe very little but it's something. Lol.
In short, We use them in my line of work to reduce turbulence at the vent in vented speaker enclosures. That turbulence can be audible which is obviously undesirable for audiophiles.
I didn't proof read my post. If it seemed as if I was talking seperation with bellmouths I should have clarified. In the applications that we use them, the radius of the flare is smaller than what you're using. A 1" radius is usually all that's required to eliminate port noise. Because air flow moves both ways in a vent, the diameter of the vent will determine velocity. A smaller vent can cause port noise caused by the higher velocity even after the flared port eliminated audible turbulence in the end of the vent..



I'll try to whip up an example of what was in my head. I'm a visual person. I can't explain anything without props. Lol.

Now I'm rambling. Thank you again.

Edit: I guess I never mentioned understanding the increased efficiency.... Bare with me. :)

[phil (admin)]

phil how much does static play in that dust hugging the sides of tube

Not much I don't think.  It is just a matter of the air moving faster through the center so the debris hugs the walls.

[Zamfir]

Great discussions!  That top hat style is neat. 
I primarily have been cutting balsa and basswood and ply and this has been great.  I am now going to be cutting a lot of carbon fiber and G-10 and have a 3 year old that likes to hang out with me in the garage.  So, I built a negative pressure room--mini clean room for my CNC to keep the dust contained.  I have been reading up a lot and I want to be sure I am containing the very fine dust the Thien separator can not spin out.  I have an old Delta 50-179 that I am going to use for the dust "room"  and I would like to retrofit the dust bag to a canister.  Is this just silly or a waste of time?  I need a new Bag filter for the old Delta and I figured I would attempt to change that out to a canister type somehow.  I will keep looking around on this site but I am having a hard time finding just a canister filter setup I can just plumb my existing exhaust into.  Any help to point me in the right direction?  I figured I would replace the bag with a Wynn filter of some sort but not sure how to patch just the filter onto the exhaust port instead of the bag. 
I would post a picture..but do not know how  ???
Thanks!
-Eric

[Lance]

Has anyone considered making a bellmouth out of PVC.  It looks like it has been done for the ports on sub-woofer speaker cabinets for some time now:

Here is a link to someone doing it and he has a how to on how its done:
http://www.subwoofer-builder.com/flares-25mm.htm

I am currently working on a mold to try it myself.  I will post info on how that works out.

[retired2]

I believe a bellmouth made this way can produce better results in a Thien tophat separator than a commercial bellmouth.  Keep the flared flange smaller than a commercial unit and you will reap nearly all the benefits of improved air flow without the increase in waste by-pass.

Commercial bellmouths have a pretty large flange diameter, and when inserted in a typical separator with a diameter around 20" I believe they can increase the amount of wasre bypass.  However, from  my experience the amount is small and I still strongly advocate their use.

[Lance]

Finally got the mold made and the press completed.  I have a fan with an 8" inlet I built for a Pentz style DC about 15 yrs ago.  Therefore, I'm basing my top hat on the 8" inlet also.  That made for a very large mold and press for the PVC.  I plan to put the end of the PVC in a large pot of boiling water to soften it then press it onto the mold.  If all goes well I will be attempting this tonight.  The mold is made of multiple layers of MDF.  I really could have used this DC up and running while turning all of that MDF on the lathe.  After turning I covered it in glue and sanded it some more when that was dry.  I figured I needed something to harden the MDF.  The 8" PVC pipe has a wall thickness over 1/4" and im guessing it will take a lot to stretch it into shape.  Wish me luck!

[phil (admin)]

Okay good luck Lance, I hope it goes easier than expected, and I can't wait to see the results.

[NCTinkerer]

I can't quite tell from the picture, are you using a solid material PVC pipe or the cellular core type?  I was going to make a wooden bell-shaped form on my lathe and push the pipe onto it using the tailstock while applying heat with a heat gun while slowly rotating.  When I went looking for pipe yesterday, all I could find was cellular core schedule 40.  I wanted the thinner DWV schedule 20 that looks like a more solid material.  I don't know if it really matters but, the solid material seemed more promising.