I'm building a small all-in-one tophat style DC for use with 3 inch (max) hose. What sort of off the shelf items can I use for the tangential inlet? A couple times in the past I have taken PVC pipe and bandsawed a taper & glue/screw it to a plastic flange but that method is extremely fussy--but it's cheap :)
In this instance the cut away portion would also need to be curved to match the curvature of the tophat body. Sounds like too much trouble to me.
Do most of you fab a rectangular box & then cut that to fit the curve? Any other nifty ideas?
Hi,
PVC is easily softened with hot air and can then be readily shaped. It can be hot air welded and glued with solvent.
The best inlet pipe is a rectangle and if the inside width is 1 1/8" it will match the width of the drop slot. If the inside height is made 6 1/4" then you will have a section area that matches your 3" tube. If you make a wooden former to these sizes that is 9" long then mould your pipe around it you will have a low turbulence inlet pipe. Once glued in place the end can be easily trimmed with a sharp knife to match the inside of the top hat chamber. Use the former again to make a transition from rectangle to 3" round pipe.
OR
If you can get 3" diameter metal trunking it is quite easy to hammer it down onto a piece of 1 1/8" wide hard wood to get the same dimensions.
OR
Make up a wooden former and use it to mould a fibre glass inlet pipe.
Form some 3" PVC pipe to give its end a bell mouth to make the outlet pipe.
Set the end of the outlet pipe down 3" from the top plate. Make height of separation chamber 9".
Ensure there are no leaks. Let us know what you do and how well it works
This should all work Regards
im sure what bernard did will work perfectly .
i needed an 8"diameter transition to 10" x 6 (i think) . at 10% to the area of the round pipe for the losses going from round to rectanguler
i decided to build one out of sheet metal (it was very expensive to buy localy) it turned out a lot easier than i first thought. there are several websites showing you how
Is there something simpler for this simple DC? This is really intended to be a low-buck, low-effort sucker for removing vermiculite from an attic.
Guy, in my TopHat application, I used PVC, because it fits the hose from my ShopVac. I formed the inner circumference of the separator with some aluminum flashing I had laying around, cut a hole for the PVC, then recut both the aluminum AND PVC a couple of times till it fit. In use, there is a little residue that collects around the edge of the PVC where it penetrates the inner circumference of the TopHat, but it's not a big deal. More problematic is the curls of wood from hand planing, that want to wrap around the 1/4" threaded rod I use to support the baffle.
Nevertheless, it works, far better than I had ever imagined such a seat-of-the-pants assembly. I doubt I would use it for a permanent installation, with duct work, blast gates, and so forth. I have a "new and improved" design in mind that will cost considerably more in parts and labor for that. But for now, my ShopVac / TopHat solution is superb for vacuuming up the detritus from my (rather successful) attempts to reduce large and expensive pieces of wood into small and mostly ho-hum works of art.
Ain't wood working fun?
PS: if you do a search on my username, you will surely find photos of my design.
I'm going to have to use rods to support my baffle--which probably means I will need to add a window or door to the tophat so I can clear any snags. So I might as well combine the 2 by making a large curved clear flange and glue/screw the inlet pipe to it, coming off at a tangential angle. I'll make it a bolt-on fitting so I can remove it to clear a clog, if ever necessary.
Metal forming is beyond my capabilities so the pipe will need to be wood or PVC. I made a hood to cover the dust slot on my Unisaw, and a hood for a portable planer like this before and the only challenge is securing the pipe to the flange so it won't break off if it gets knocked. This will be especially important on a pipe with a hose attached. I'll figure a way to reinforce the attachment with some ribs or something.
My planer hood:
(http://i170.photobucket.com/albums/u273/guy48065/Shop/2012hood_zpsec412658.jpg)
If I felt more comfortable working with steel I might try something like this as an intake:
(https://s3.amazonaws.com/ljimg/mjs1aqg.jpg)
(Thanks to Lumberjocks.com for the idea & photo)
It's just a floor register boot and I believe I've seen them made with a deeper rectangle section that could be cut to fit the curve of the tophat, and maybe notched & flanged for attachment. Hmmm...
Instead of a long oblique cut to the pipe like I did to my planer hood, what if I were to insert the pipe whole into the tophat through a long oval cutout? This would make the mouth of the inlet round like on the original baffles with the elbow inlet. This would change the dust trajectory from tangent to the sidewall to a chord. Would performance suffer much?
Dunno about performance...but probably. the other thing that happens when you stick the pipe into the cyclone, you make "traps" where junk collects but doesn't drop into the collection bin.
I decided to go with the "cheap" option. Money is a little tight and with all the recent rain I've been stuck indoors anyways so I had time to figure out the fit.
Hi, Might be inexpensive but it looks fine. Hope it works out.
with a bit of fine tuning that will work perfectly
nothing wrong with a low cost solution
Nice job.
Paul
I'm pretty disappointed in the performance so far. This is a pic of the chamber before attaching the baffle. It's an 8X22 chamber with a 4" inlet & 3" outlet. 1 1/8" slot. A 3-stage 12" radial blower sits on top. If memory serves the blower/motor is rated for 600CFM at 12" static. I flared the chamber outlet & located the rim 1 pipe diameter from the baffle. The baffle is 1/2" ply with the edge tapered.
I forgot to take pictures of it assembled so that will have to wait. Anyways with an open intake I see dust swirling around endlessly inside the chamber so it's pulling that up from the drum below. If I add chips they do thin out in the chamber--but not instantly as I had hoped. Tested with fine powder like MDF dust, a bit can be seen exiting the exhaust. If I introduce a scoopful to the intake all at once a large amount spews out the exhaust.
I had better results with the previous incarnation which was a 20 gallon steel drum with a basic 2.5" elbow hanging from the lid in an ordinary separator configuration.
i had similar results with my seperaters when i first use them. it happens usually because of leaks . everytime the leak is diferent. its hard to tell you how to fix it without seeing it
get it all seeled up and it should improve . mine always do
The only spot not caulked is the fit of the chamber to the drum. It's a snug fit but I'm sure some air leaks in. The only way to fix that is to rebuild it with a gasketed sealing ring. That was my intention but during a brain fart I cut the inlet into the wrong side of the chamber so I had to flip it over. There isn't enough chamber height to add a ring below the inlet pipe. I can't save anything except the baffle plate because everything is glued together with Quad Caulk. Fortunately the materials are very cheap. This has taken the wind out of my sails --mostly because I don't understand why it doesn't do what it's supposed to. I feel that I'll end up in the same place if I rebuild it. Honestly I got so little bypass when this was a simple separator that the first "filter" was just a tube sock--and I never needed to empty it.
Could it be a mis-match between the blower & chamber capacities?
(http://i170.photobucket.com/albums/u273/guy48065/Shop/dcdone_zpsa5386d49.jpg)
i think you could add another ring all around for the seperater to sit on the trash can. then put weather stripping on that
It's already a snug fit--how would sealing it up tight keep dust from being pulled from the can into the chamber? I'm just not "getting" the cause of the reverse flow. BTW the can is empty except for an inch of dust so there's some serious activity in there to re-animate it and move it from a low pressure zone to a high pressure zone.
Quote from: guy48065 on May 02, 2013, 09:22:40 AM
The only spot not caulked is the fit of the chamber to the drum. It's a snug fit but I'm sure some air leaks in.
Is the top hat just pushed down into the garbage can? That has to be perfectly sealed.
when i was sealing up my latest seperater i used armaflex pipe insulation tape. it is soft like draught seal but sticks to everything.
i went all around in short lengths (because it is hard to work with because it sticks to everything amazingly well)
one small section about 3 " long got stuck to the bench and pulled off when i lifted the seperater.
i didnt spot it at first.
i put the seperater on top of my half full can adn fliped the switch
you could see where the air had rushed in throught the small gap. it 'cut' a slot into the chips and send them up into the seperater and out to the dc.
the dc was not vented out side at that point. it was like i had tipped the barrle from the roof top. there was dust everywhere. so much so that i had to evacuate the shop and wait for it to seetle then vac the whole shop up
Quote from: phil (admin) on May 03, 2013, 02:36:20 PM
Quote from: guy48065 on May 02, 2013, 09:22:40 AM
The only spot not caulked is the fit of the chamber to the drum. It's a snug fit but I'm sure some air leaks in.
Is the top hat just pushed down into the garbage can? That has to be perfectly sealed.
The top pushes down into the can. It's sized to be snug but not a force fit so I'm sure there's some slight leakage. I assumed leakage here would be of no consequence other than the minimal reduction in CFM. I've also read older posts about leaky tophats where there were no complaints of negative efficiency (more dust going to filter than taken in at inlet). I guess I drew the wrong conclusions from this.
Adding a 1/2" ring + weatherstrip under the inlet pipe should still leave me with enough wall down inside the can. The hope is that I can do this and not have to start over with a new build.
I'm sure getting a lot of unexpected use from the circle-cutter jig I built for my bandsaw :)