J. Phil Thien's Projects

I never built an "original" Thien "elbow-type" separator...instead, I went right to the top-hat concept. So I can't comment as to the effectiveness of the elbow design--obviously it works or Phil wouldn't have shared it with us.

But I can say that the top-hat concept is close to 100% effective. At least with a shopvac. I'm still confused about the issue of pipe size, and all the other stuff.


ETA: Doug, do you have Sketchup? I'm glad to share my sketchup drawing for my tophat design.

So.

I'm not so new to the forum, but I am new to setting up a dust collection system. I read (and try to comprehend) everything in the several wood working forums I belong to on the subject.

And I am still confused.

Not about the value of installing a system--there are many and varied and often contentious threads on that subject. That dust collection is necessary (or "a very good thing to have") isn't in dispute. I believe that ANY dust collection system is better than no dust collection system. And I think galerdude is spot on saying that improving whatever system is employed in a shop is an ongoing endeavor.

No, my confusion is on what components I should incorporate in my own (and no doubt unique--or nearly so) system.

Based on more comments that the HF "2 HP" unit is a "very good value" and that I "won't be disappointed in the investment" I bought one. Out of the box, it's . . . meh. I mean, it sucks up "some" dust and chips and deposits most of it in the poly bag. But the filter bag is just pure garbage. There is no question that better filtration is required. It's obvious that modifications to the HF unit are required to improve dust collection.

I am 100% convinced that Phil's separator design is the cat's meow. I built one for use with a Shop Vac and am thoroughly impressed by how well the thing works. I will definitely install a similar device in my central DC system.

So maybe that's half the confusion cleared up.

The investment in a Thien separator and the HF unit is <$200. The budget director is pleased. But I haven't told her yet what the bill for the piping and gates and fittings and all is going to amount to. Way more than two hundred bucks!

Like most everyone, ultimately, I waded through Bill Penz's dissertations on dust collection, looked at what all the other pundits and number crunchers have to say on the topic. I became thoroughly frightened that my $200 investment was a "bad idea" and I should have hocked the Volvo and my pickup truck to buy a more powerful system. But if I admitted that, my standing with the budget director would be on very narrow footing. (She really likes the Volvo.)

One pundit says, to effect: "You can't move enough fines through anything smaller than a 6" diameter pipe." Another says, to effect: "It is impossible to move the output from your table saw or jointer planer with less than 400 CFM and that's not possible in 4" pipe." And: "don't use elbows, they destroy system performance." And so on. I know you've all read the same stuff.

So, having designed the DC layout for my shop using 4" pipe, I redid it using 6" pipe. I also bought a length of 2729 S&D and fabricated 90? and 45? sweeps. (Translation: fun with a bandsaw and several packages of JB Weld.)

Then I visited the Woodcraft store that isn't near to me, but is closer than any other, and looked at their classroom shop. It's approximately the same size as mine, has approximately the same compliment of machines, and it's plumbed all in 4" S&D, with those ubiquitous cast aluminum gates and there must be as many if not more fittings than I plan, and half again as many feet of run. I asked the guy there at Woodcraft how well the system works.

He said, "It works very well."
"It picks up all the dust?" I asked.
"Yep," he said. "Why?"

It was then that I laid on him my load of confusion (basically what you read above), and he just shrugged and repeated that their system works fine. Apparently, they use a 3 HP cyclone. I didn't see it, nor do I have any information as to the FPMs or CFMs, which I believe are more pertinent than the power of the motor driving the system. I also don't have any data on how many gates might be open at once in that classroom. I plan on using my HF thing with a Thien separator in front, and (when the budget director approves, a cartridge filter, such as supplied by Wynn). And as I work alone, there is no reason to have more than one gate open on my system at a time.

So now here I am, looking at these gorgeous 6" sweeps (well they're not gorgeous, really, but the are pretty cool), and am wondering if I'm obsessing about the thing too much. What if I did revert to the 4" layout (using similar sweeps in lieu of elbows)? It would certainly please the budget director.

The thing that gets me is this: If I invest in 6" pipe, what happens at the machine? The ports (or the logistics of space for anything larger) are all 4" or smaller. So isn't that the weak link? The inlet on the impeller of the HF is 5". I love physics but I'm not very good at it, yet I seem to recall that in a fluid system such as an air duct, as volume increases, velocity decreases.

If dust-laden air is sucked into a 4" pipe that fairly quickly grows to 6", things slow down. No? At some point, the little Chinese motor and 12" impeller at the HF unit are just not gonna be able to keep up. No? (Then I read that inserting a separator of any kind impairs the system even further. Yet I will have one of those!)

Here's my proposed layout:

Okay, enough lurking.  :)

I'm designing a top hat separator for a HF DC unit. I'm gonna turn the impeller/motor unit on its side and abbreviate the run to the filter. Same old, same old.

I have already built a top hat thing for my shop vac, which I used 2" PVC inlet/outlet. It works. But it isn't a DC.

Originally, I had designed the thing for 4" duct, but enough pundits have complained (we all know their names) that 4" isn't big enough to move dust adequately, so I'm reconfiguring everything to 6". This despite the Woodcraft Supply class room I visited over the holidays that used 4" duct throughout and the claims by the staff that it "works great."

So my top hat design for 4" duct is 6" high from baffle to top plate, and the 4" to rectangular devolvement makes a nice narrow entrance into the separator, forcing the dust-laden air against the circumference wall. Well, I said to myself, I will just enlarge the opening to accommodate the 6" pipe.

My assumption is that the area of the pipe must be maintained regardless of the cross sectional shape. I didn't change the internal height (6") but just divided that into the 28+ square inches of the 6" pipe to arrive at a rectangle about 6" x 4.5". (My math was more precise, but that isn't the issue here.) What happens is that the edge of the rectangle nearest the center of the separator cylinder is REALLY close to tangent to the outlet (5" --  HF unit, remember?). I want to put in a bell mouth exit because the comments about that elsewhere here in these forums are compelling.

So my question is this:

What is more important? Concentrating dust-laden air near the outer circumference or maintaining a shallow internal height between the baffle and top plate?

I don't see any images either.
Windmill did include image links, but to a forum that requires membership to view them. (You can see the links if you "quote" the original post.)

I used aluminum flashing and beads of silicone sealant on my first separator. No problems (with that, anyway). If you begin with a coil of metal and install it "against" its already coiled direction, the metal will want to open up against your plywood stop. A couple beads of ordinary clear silicone caulk/adhesive will be plenty good to hold it in place. After all, you're not depending on the metal as a structural element; the plywood enclosure shown in your photos does that.

+1 on the construction, too, btw. Very nice.

/begin rant.

I saw the Thien separator somewhere (maybe it was SMC) and thought to myself: "Self, that's a mighty neat idea. You should find a way to use it."

So I did. I "invented" the top hat. Of course then I found this site and discovered that about 78 bazillion other guys had already "invented" the top hat, and if that wasn't amazing enough, there are 32 oodles of threads all about how to make them work better. Or differently. It's getting to the point where if you have a hankering to become thoroughly confused, seek out dust collection forums and try to come up with some single solution for your particular condition.

My friends: there ain't no such thing.

But of the myriad solutions possible, some of them are damn good, and of those, there will be duplicates. Yep. Copies of that "very cool design" you just came up with because if you're like me, you're too damn lazy to go do hours and hours of research necessary to find that you've just reinvented someone else's wheel.

How many hours have YOU spent on your design(s)? I've spent hundreds of them. Are my solutions unique? Hardly. But you know? When you go about inventing the wheel, you're gonna come up with a circular device that pivots on some sort of axle and if you're concerned about comfort, may have a tire. Or if you're concerned about aesthetics, it may be chromed.

But it's still a wheel, which, last time I checked, was in the public domain.

Now Mr. Thien's designs are probably not completely in the public domain, but those modifications of it we all make in hopes we'll solve our particular problems (cost, available materials, time, energy, motivation, brand of shop vac or dust blower) will make the design different.

I've lurked in this place awhile. I've posted a couple of times. But whereas the separators people here have built all work on a similar principle, they all differ from one another that there is NO plagiarism.

And if anyone wants to copy my design, I say GO RIGHT AHEAD...and while you're at it, see if you can find a way to make it better. If you do and tell me about it, I will be forever grateful.

/end of rant.

Thanks for reading. :)

I seem to recall reading that someone used what amounts to one of those wire cages used to support tomato plants inside his trash can below his separator to keep the garbage bag liner from being sucked up into system. I think a section of wire fencing rolled into a cylinder to match the shape of the can might work as well. Anything to avoid emptying 30 gallons of loose sawdust is a good thing.

Mrgedman, my intake is not really like your number 5 illustration, in that the pipe is tangent to the inner drum, like your number 4. The dust that collects around the pipe is above and below it, not to the sides as you indicate with the small x marks. And it isn't a great collection of dust--probably in the range of a couple tablespoons-worth. Photo attached.

I agree with retired2 that for a shop vac, the design of the intake is not terribly important. I certainly don't worry about the small inefficiencies inside the separator. What's more important to me, is the nearly zero amount of dust that arrives in the shop vac. The photo attached shows the interior of the shop vac after I had used it to fill a 30-gallon metal garbage can with debris. You can see that the small piece of baggie did not find its way through the slot, but wound up in the shop vac. That happened once.

Now, for the dust collection system I'm designing for my shop, I will pay considerably more attention to details in the separator. I will use a rectangular duct that in plan, at least, matches mrgedman's option #4, but which will be full height of the drum. Anyone reading this who has experience that indicates this is a bad idea, please comment. From what I've read, a shop vac has considerably higher air velocity, but handles less volume than a dust collection system. My shop vac/separator configuration will suck up 1/2" hex nuts through 20 feet of 2 1/2" hose. My 2 HP dust collector will move immense piles of sawdust out of my table saw, but won't pick up anything with significant mass. As it should be: a dust collector is not a vacuum cleaner. :)

I made my a top hat separator for my shop vac. It occurred to me that if I didn't make some way to get into the thing, then it would be extremely difficult to remove anything that might obstruct the works. Indeed, after completing the thing, I delighted in demonstrating its effectiveness by sucking up all sorts of garbage--and sure enough, I sucked up some hand plane curls and the like and a plastic bag. (I used it on leaves on the patio, too. That works great.) Needless to say, these large objects either wouldn't drop through the slot or wrapped around the support post inside.

I was glad that I made the top removable.

It isn't difficult at all. Basically, I put the cyclone and baffle in a plywood box where the top and bottom extend beyond the sides. I then used 1/4" threaded rod at each corner to hold the top on, and for the post that holds the baffle from flopping around inside. Lock nuts keep the rods in position on the bottom of the box, utility knobs allow me to quickly open it up to get out stuff that I probably shouldn't be sucking into my separator, but do anyway.

To seal the top to the box, I made a gasket out of some of that white foam packing sheet. Leakage? Not much: When I first turned the thing on, it collapsed the 30-gallon galvanized garbage can I have the top hat resting on.

-----------

As for your dilemma with intake, I imagine there is very little difference between the worst of your four options and the best. My design is most similar to your option 4, except my pipe extends into the drum. The only time I have to clean out the shop vac is when I've clogged the slot (as in the examples above). Otherwise, it apparently separates everything out of the air--well, everything I can detect, at any rate.

However, I find that there is quite a bit of dust piling up around the circular intake pipe, above and below it. I don't have the skills (or didn't then) to fit the vertical cylinder of the drum to the horizontal cylinder of the intake pipe.

I am currently designing a larger top hat, for use with a dust collector (as opposed to the shop vac). This time, I think I will make a metal transition from the round pipe of the system to rectangular intake in the separator. I an not a pneumatic engineer, but my supposition is that such transition should be gradual, rather than abrupt, that the area of the rectangular section should equal or exceed the area of the pipe. This would preclude just flattening a section of duct, as doing so reduces the area significantly.

My understanding of the way this thing works is that we want airborne particles to collide with the sides of the drum, reducing their velocity which causes them to drop out of the air stream, which ultimately winds up in the center of the drum and is evacuated by the fan. Therefore, anything that can be done to concentrate the particulate stream at the extreme diameter of the interior is preferable.

It is indeed possible to collapse a 30-gallon can with a Shop Vac. I did it. Twice. The second time, the walls of the can touched. But I had already built the seperator and I wasn't very interested in buying a new can...so I pushed the can back into shape and added external stiffeners to strengthen it. I used some scrap 3/4" plywood to make two rings around the can, dividing its height into thirds, and put a #6 x 1/2" screw in each rib of the can. I didn't seal the screws. There is so much leakage now, that I doubt the can would collapse even without the ribs. But I have noticed that the vac no longer picks up heavier objects, such as screws, nails, etc. This is mostly okay by me--I really just want to remove sawdust from the shop. I suppose that if I sealed all those screws, it might suck up screws.

Here's a photo:


But as it is, it gets all the dust! And almost none goes into the Vac--just the talcum-powder-fines.