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

[retired2]

looking at your metal intake do u think it would have been better to extend it into the chamber and cut it off on the same cir. as the inside dia. im just wondering what kind of turbulence it is at that point from your test.

There is absolutely nothing to be gained by extending the metal intake of a rectangular intake port.  A rectangular intake, if done like mine, is flush against the walls, ceiling, and floor of the separator, so the separator itself forms the intake port.  All that would be accomplished by extending the metal port is to add the extra work of cutting the circular arc.  And then you would just be covering separator material with a skin of metal, but the inlet would be still be exactly the same size and shape. 

Now a circular intake port is a totally different story.  There you want to cut the end with an arc that matches the separator because the intake is round and it does not match up to the walls, ceiling and floor of the separator the way a rectangular intake does.

[retired2]

one other thing i see where you added a 3/16 t-rod. what do u think of just attaching the rod to the bottom of the can so that the baffle will just sag and rest on top of rod

It would work, but I don't want anything that complicates the task of pulling the drum and emptying it.  I'm already working on a design that does not require me to disconnect any hoses or piping.  The drum will drop down from the slot and then slide out to be emptied.  The process will be reversed to put the drum back and seal it.

[retired2]

Well, I made a little progress in the past two days, but I also had some problems.  Two things I would do different at this point:  First, I would not use water base paint again - it takes forever and a day to harden (actually it never does).  Use oil base and just throw the brush away!  Secondly, I would not use plexiglass again, it cracks far to easily.  Ironically, it can be bent in a very tight circle with no problems, but drill a hole in it and it becomes as fragile as glass.  Next time, I will use polycarbonate.  Here's some progress photos, I may have one or two more tomorrow evening.


In this photo I am using a slot cutter to cut a 1/8"w x 3/16"dp dado in the top and bottom plexiglass retainer rings.  The slot will be used for sealing the plexiglass.




Here I'm inserting rope caulk into the dado to seal the plexiglass.  I decided to use the rope caulk because it was the only thing I could think of that would stay put without running or dripping.  The rope caulk is not an adhesive, so I will retain the plexiglass with screws.



And here is where disaster struck - not one, but two vertical cracks.  I was extremely careful not to cinch down the screws because I knew this can be a problem with acrylic.  Interestingly, both cracks occured at a vertical rib.  I soaked the crack with crazy glue and it seems to be holding, but if it gets worse, I'll be replacing the acrylic with polycarbonate (Lexan).  Before I decided on truss head screws, I did some testing with countersunk holes - don't even think about it!

[Bulldog8]

I used plexi or polycarbonate in mine. (it was laying around the shop and I don't recall which type it was)

My build was similar to yours in that both ends of the plastic are captive. The captive ends held the plastic in place. Therefore, I don't understand the need for screws. Did you use the screws simply to ensure that you had a good seal against the Moretite?

Steve

[retired2]

I used plexi or polycarbonate in mine. (it was laying around the shop and I don't recall which type it was)

My build was similar to yours in that both ends of the plastic are captive. The captive ends held the plastic in place. Therefore, I don't understand the need for screws. Did you use the screws simply to ensure that you had a good seal against the Moretite?

Steve

Yes, the screws were added just to keep it sealed against the rope caulk.  My thinking was that under vacuum it might flex enough to allow small air leaks.  Maybe I should have just tested it without the screws because the plexiglass is really fit in very tight, and as you say it is held captive at both ends. 

[Don_Z]

The cracking was an issue that I was having with mine as well. After the 3rd retry I used a clamping caul of the inside radius to slowly bent the acrylic into shape then very gently set the screws in by hand.

[retired2]

The cracking was an issue that I was having with mine as well. After the 3rd retry I used a clamping caul of the inside radius to slowly bent the acrylic into shape then very gently set the screws in by hand.

This whole plexiglass/polycarbonate design is an area that needs more work by some great minds.  It seems everyone is having their share of heartburn trying to make it work.  When I set mine in place, I warmed it with my wife's hairdryer.  That was plenty of heat to shape it and ease it nicely into place, but of course as I found out that's the easy part.  Sealing and securing it is where it gets a little hairy.

One "off the wall" idea I have is to rout a rabbit in the plexiglass retaining rings just as I did, but not fill it with rope caulk.  Then from the outside of the retaining rings drill holes radially into the rabbit every six inches or so.  Then set the plexiglass in place, and make sure it is seated, clamp lightly if necessary.  Then using some yet to be determined product that would act as both an adhesive and sealant, inject it into the radial holes and let it fill the rabbit from the outside. 

O.K.  folks, there's a challenge, go to work on that idea and give us a report!!!

[phil (admin)]

A clear polyester would machine much easier, IMHO.  And would be much less likely to crack/shatter where fastened with a screw.  Problem is, all you can typically find in stores in acrylic ("Plexiglas") and polycarbonate.  The polyester products fall between the two of these for durability.  But the polyesters are very machinable and moldable.

[retired2]

Finally.  Here's the photos of my completed separator.


This photo shows the rod I added to stabilize the baffle plate.  It might have been O.K. without it, but I didn't think it would have any effect on the performance of the separator, so I installed it now.



And here's the finished product.  I used rope caulk to seal the inlet pipe, and I will do the same with the outlet pipe.  When I'm sure I won't be making any more changes, I will replace the rope caulk with something more permanent.



So, now you all expect to get some immediate test results.  Wrong!  I want to relish the belief that this thing is really going to work well for a while longer.  Then I'll risk shattering that hope with real world testing.  Actually, the real reason for the delay is pictured below.  (See later post for video of test).  I need to raise the DC up on a fixed support and then finish the piping system. 

[Don_Z]

When setting the screws, I chose to countersink them to reduce any turbulence and used a #4 1/2" flat head with a fine thread. When working with acrylic, you just have to remind yourself that it still is a very brittle material and you cannot torque fasteners into it like normal and that you have to ease them into place. If you see it flex, you are going to hard and it will fail. On my first attempt at a separator I tried the whole dado slot for the plexi, and it a real pain in the rear to get it in place if you are wanting to get it in there tight.

[retired2]

FIRST TEST VIDEO

O.K.  Guys, I couldn't stand it any longer so I did a quick and dirty hook-up of my new bellmouthed outlet, rectangular inlet separator to see what happens.  All I can say is the preliminary results look very promising, but the jury is still out.  I don't want to speculate on the improvement the bellmouth makes, but the good news is it certainly hasn't hurt.  I think it might be safe to say a rectangular (taller than wide) inlet is the way to go - it puts the dirt immediately against the outside wall and over the drop slot, and there seems to be less turbulance where the two airstreams converge. 

When I complete the modifications to my DC support and eliminate much of the flex hose, I will do more extensive testing using an ammeter.  I'm hoping the ammeter will tell me something about the performance of the bellmouth outlet versus a straight pipe.  I'm also hoping it will give me some idea how much loss the separator is introducing.

So, here for your enjoyment is a video of my first test.  I apologize for any quality problems because I was holding the camera with one hand and feeding dirt with the other.  The dirt being fed in is pine shavings from my thickness planer.  My guess is this material is one of the easiest for the separator to handle, but not a single chip by-passed the separator.  That's great news because my worst fear was the bellmouth would upset the internal dynamics for some reason and allow a lot of dirt to bypass the separator.  I didn't use pine chips to bias the results, it is just what I had on hand.

Give the file a minute, it is big.

https://www.dropbox.com/s/n6x7xrekgf2l33y/Separator.MPG?dl=0

[Don_Z]

Sweet!  :o I tested mine having nothing hooked up but the motor and threw handfuls of fine mdf dust and nothing came out the other side, the separator worked like a champ. Unfortunately I am going to have to hold off on giving it the paint job I wanted until after I get the wife her new kitchen (that I put on hold while I made this thing.) After all, orders are orders.) I think when I do paint it, I will repaint my other equipment as well as I am going to be cutting 5" ports all of them. Maybe a nice flame job or something hot roddish.  8)

[phil (admin)]

Very nice work.  Looks like you have a winner there.

[retired2]

Unfortunately I am going to have to hold off on giving it the paint job I wanted until after I get the wife her new kitchen (that I put on hold while I made this thing.) After all, orders are orders.) I think when I do paint it, I will repaint my other equipment as well as I am going to be cutting 5" ports all of them. Maybe a nice flame job or something hot roddish.  8)

Don, I'm no expert on separators, but I'd be willing to bet they work as good without paint as they do with it.  :)

[retired2]

Very nice work.  Looks like you have a winner there.

Thanks for the compliment Phil, but you are the one that provided the rest of us with a solid design for a truly innovative idea - we're just monkeying around with tweaks.