Hi, thanks for making the plans available to us all. I was thinking to build this for myself but found http://www.pellvac.com/s/askcyklon.php (http://www.pellvac.com/s/askcyklon.php). Different, but similar. It isn't cheap, though. Apparently from the 70's, see http://www.pellvac.com/pdf/artikel%20uppfinnaren%20och%20konstrukt%f6ren.pdf (http://www.pellvac.com/pdf/artikel%20uppfinnaren%20och%20konstrukt%f6ren.pdf). Now, to the question: The aperture is much larger in the whirlwind, and has no solid part. What difference does this make, if any?
Quote from: jalar on January 14, 2013, 08:59:49 AM
Hi, thanks for making the plans available to us all. I was thinking to build this for myself but found http://www.pellvac.com/s/askcyklon.php (http://www.pellvac.com/s/askcyklon.php). Different, but similar. It isn't cheap, though. Apparently from the 70's, see http://www.pellvac.com/pdf/artikel%20uppfinnaren%20och%20konstrukt%f6ren.pdf (http://www.pellvac.com/pdf/artikel%20uppfinnaren%20och%20konstrukt%f6ren.pdf). Now, to the question: The aperture is much larger in the whirlwind, and has no solid part. What difference does this make, if any?
I think the battle with that unit would be that it would only marginally improve scrubbing. The aperture is just too wide and as the unit fills, too much stuff is going to make it through to your filter.
If you notice, there is a line on his bin, the "fill-line." Anything above that will probably just make it to your vac.
If you watch the entire video, at the end they remove the bag from their vac, but they're careful not to tip or shake it. And it seems to have some weight to it already, too.
They do list their separation to be 99% so I'd expect some dust to make it to the bag, yes. But they claim it is efficient for fine dust too. What is the efficiency of your construct?
jalor
i dont know the efficiency of phils design . iv ran mine with no filter(will be vented outside) for a while (i am only setting it up)
i dont notice any dust in the shop (other than what was already there)
i put some ploistyreen into the pipe to see what would happen.
it was all seperated . . there was none anywhere esle . i was expecting a shower of balls but nothing
just because they say 99% efficient doesnt mean anything.
they are bount to say that. i would like to see a review by a trusted reviewer
i like the look of that seperater.
its a shame the top part isnt the size of the whole lid. it would probably seperate better
the baffel plate part is easily fixed
I suspect a larger radius would make it worse for the fine dust. There are larger versions, for "industrial" use, biggest tank they use is 25 cubic metres 8). Pellvac's own use is for ash and wood-pellet dust in their vacuum wood-pellet-handling system, so it is aimed for fine dust, not coarse.
They claim 99 percent for talcum powder, I'd expect larger chips to be better separated. There is a video on youtube where they use it on wood-pellet ash: 1 kg of ash through the thing, and 8 grams make it through. There is also a referece to a test at Chalmers (technical university), but I have still to see the report.
I do want to use mine for ash, so it makes a big difference if it handles fine stuff or not. I might buy one and try it out.
maybe this company is teling the truth. there have to be a few at least
if you buy one please let us know.
i too could do with a seperater for ashs and sut
Quote from: jalar on January 15, 2013, 02:13:36 PM
I suspect a larger radius would make it worse for the fine dust.
There are "sweet spots" for the size/mass of the debris you're separating, and the amount of CFM you're using. The "sweet spot" will dictate the size and shape of any baffle, and the radius of the separator.
As the debris becomes finer, the baffle's slot width can be reduced. The slot should be sized to about 1.25 to 1.5x the largest piece of debris you envision separating (with exceptions for extremes). That is, if you're separating ping pong balls, you don't size your slot for tennis balls. I sized the slot of my original unit at 1.125" to accommodate typical hand-plane shavings.
Provided one sizes the slot appropriately, you can increase the radius and experience a reduction in resistance introduced by the separator, and reduce short circuiting (where incoming debris immediately moves to the exit port and leaves, without entering rotation).
The unit you linked seems to use a relatively small hose (1-1/4"?). Upsizing it to 2-1/2" (with the corresponding increase in CFM you might expect if connecting it to a higher-powered shop vac) may result in quite a hit to CFM (lots of resistance, which is proportional to the speed of the airstream squared). In that case, increasing the R would decrease resistance, and it might even increase the separation rate (by reducing short-circuiting).
With the 1-1/4" hose, it may be right-sized (radius-wise), but not baffle-wise.
The baffle is just way too small, and baffles should never be symmetrical as that one. It allows the air above the baffle to couple to the air below the baffle too effectively, and spin that bottom air mass. With the baffle being as small as it is, and being symmetrical, I can imagine running it for long periods would allow scrubbing.
The best way to detect scrubbing is with your ear. Put your ear to the hose between the separator, and your vac. Those "tics" you hear are debris sneaking through the separator. You should hear no "tics."
phil.
im thinking of building a seperater for my vac (festool ct22) and building a boom arm.
from reading that last post (some of which i hadnt read before .
i have a 50 gallon drum (same as i used for my 6 " version.)
if i made the top hat the fulll size of the lid but with a 3/4 "(maybe) slot all around.
would that work and have the lowest resistance and less losses
Quote from: alan m on January 15, 2013, 04:24:04 PM
phil.
im thinking of building a seperater for my vac (festool ct22) and building a boom arm.
from reading that last post (some of which i hadnt read before .
i have a 50 gallon drum (same as i used for my 6 " version.)
if i made the top hat the fulll size of the lid but with a 3/4 "(maybe) slot all around.
would that work and have the lowest resistance and less losses
I never really went to the extreme of a 50-gallon being fed by 1-1/4" hoses (which restrict the CFM). I think it would work fine, though.
The problem with a 3/4" slot the full circumference of the baffle is the coupling of the air masses above and below the baffle. As the level approaches the bottom of the baffle, you will see more scrubbing.
sorry i meant with the solid part like normal.
i wrote it a bit funny because i was thinking about tapered slots
if i was doing it it would probably be 50mm inlet and outlet to suit my ct22
i would mostly be using it on my festool portable power tools and my12" disk sander
it would be mostly sanding dust or small saw dust.
im not sure what to do
1. use the 50 gallon drumm . (i have 6 sitting there. one for the 6" seperater and 5 spare). it would mean having the same type drum so if the 6" filled and i needed another rum quick i could swap over. but it would take a year to fill or more
2. use a small drum but when its full i would have to empty it straight away. i would also have to find said drum
All I know is I wouldn't want to lift a 50-gallon drum filled with sanding dust. Chips from a planer wouldn't be that bad, but sanding dust packs a drum much better and the weight would get more than I'd want to lift.
I'm not sure it needs a big baffle.
As I understand it from your explanation here, the baffle is meant to separate the air mass above the baffle from the air mass below. This is to keep stuff from re-entering up through the aperture, and perhaps make it out the exit. I think that is a sound idea.
But there may be a good reason that separation is good in this "short cyclone" too. There is a big aperture instead, so that the air below the separator also moves, perhaps somewhat slower than the air above. And importantly, there is an outer rim to the lid at the same height as the separator (the cyclone is not as big as the lid). This means that dust that has gone below this level is forced out, and is hindered from entering the air stream above that height (perhaps not completely, but anyway). The center vortex is blocked by the disc, which this guy calls "vortex breaker" (rather than baffle), so stuff cannot be lifted in the center either. Since the two air masses move at approximately the same speed, I suspect this reduces the turbulence in the interface between the two air masses (above and below the vortex breaker), and this is a good thing. I think the principle is sound here too.
Different principles, similar end result. Now I'm wondering whether there would be a benefit to using both mechanisms in the same device. Perhaps put a baffle at a distance below the vortex breaker, with the appropriate diameter. I might try this out.
i dont know if it will help but try it and report back.
Quote from: jalar on January 16, 2013, 01:09:50 PM
I'm not sure it needs a big baffle.
Definitely bigger baffles work better than smaller. I've tested both, there is no comparison, in this case bigger is always better.
Quote from: jalar on January 16, 2013, 01:09:50 PM
As I understand it from your explanation here, the baffle is meant to separate the air mass above the baffle from the air mass below. This is to keep stuff from re-entering up through the aperture, and perhaps make it out the exit. I think that is a sound idea.
It is a little more complicated than that. Once debris falls below the baffle, we want it to settle and stay settled. Any reanimation of debris (especially fine dust) gives it a shot at re-entering rotation and being sucked out. So the baffle decouples the air masses above and below itself, and we try to keep the air below spinning as slowly as possible, relative to the air above the baffle. This makes it much more difficult for fine dust to be resuspended and exhausted. It also causes the greatest differential possible along the slot, so the slow-moving air below the baffle literally "snatches" fine dust from the fast air moving above the baffle.
Beyond that, we want the baffle to keep anything that IS resuspended as far from the outlet port as possible. Close to the outlet port, things get pretty chaotic, with slow-moving areas, rotation changes, etc., allowing fine dust to sneak right into the outlet stream.
Quote from: jalar on January 16, 2013, 01:09:50 PM
But there may be a good reason that separation is good in this "short cyclone" too. There is a big aperture instead, so that the air below the separator also moves, perhaps somewhat slower than the air above. And importantly, there is an outer rim to the lid at the same height as the separator (the cyclone is not as big as the lid). This means that dust that has gone below this level is forced out, and is hindered from entering the air stream above that height (perhaps not completely, but anyway). The center vortex is blocked by the disc, which this guy calls "vortex breaker" (rather than baffle), so stuff cannot be lifted in the center either. Since the two air masses move at approximately the same speed, I suspect this reduces the turbulence in the interface between the two air masses (above and below the vortex breaker), and this is a good thing. I think the principle is sound here too.
Different principles, similar end result. Now I'm wondering whether there would be a benefit to using both mechanisms in the same device. Perhaps put a baffle at a distance below the vortex breaker, with the appropriate diameter. I might try this out.
I've made at least 50 separators, and I've done designs very similar to the Virvelind, it isn't an academic question, I'm speaking from experience.
The reason they have that max fill line painted on their bucket is because they need it. Above that line, a similar design I was testing passed pretty much everything to my shop vac. And even below that line, there was plenty of scrubbing going on.
Remember that the Thien separator allows you to fill right to the bottom of the baffle (and a little above, actually). And you can run it continuously without fear of scrubbing. Test designs with small baffles scrubbed like mad, you certainly wouldn't want to run them when you are not running tools.
You can go the Virvelind model if you like, just mind that fill line, and turn the unit off as soon as you stop generating dust.
Quote from: phil (admin) on January 16, 2013, 04:50:13 PM
Definitely bigger baffles work better than smaller. I've tested both, there is no comparison, in this case bigger is always better.
In constructions based on your principle, yes. And as I said, that principle is sound.
Quote from: phil (admin) on January 16, 2013, 04:50:13 PM
It is a little more complicated than that. Once debris falls below the baffle, we want it to settle and stay settled.
Agreed, I just didn't write that.
Quote from: phil (admin) on January 16, 2013, 04:50:13 PM
Beyond that, we want the baffle to keep anything that IS resuspended as far from the outlet port as possible. Close to the outlet port, things get pretty chaotic, with slow-moving areas, rotation changes, etc., allowing fine dust to sneak right into the outlet stream.
Yes, and in the short cyclone, this is achieved by a tangential inlet far from the vortex breaker.
Quote from: phil (admin) on January 16, 2013, 04:50:13 PM
I've made at least 50 separators, and I've done designs very similar to the Virvelind, it isn't an academic question, I'm speaking from experience.
So is this guy. He's not an academic, he's a hands-on inventer.
Quote from: phil (admin) on January 16, 2013, 04:50:13 PM
The reason they have that max fill line painted on their bucket is because they need it. Above that line, a similar design I was testing passed pretty much everything to my shop vac. And even below that line, there was plenty of scrubbing going on.
That's because the top part of the container is part of the cyclone. Which is why I was wondering if a baffle at the bottom of that would improve things further. But as you pointed out, there is nothing like an experiment to find out.
Well, I've explained why bigger is better for baffles, while smaller is better for slots.
You mentioned following the VV design and adding a baffle below it (I assume some inches). The baffle, in that case, would act like a false bottom, slowing the passage of debris to below the baffle. Any debris that hangs above the baffle (above the fill line of the unit) will get scrubbed from the unit more than if you just allowed it to fall to the bottom of the drum.
Give it a shot, though. Just don't blame the baffle when it makes things worse, as you won't be using it as intended.
It isn't too difficult to "mentally model" this stuff, BTW.
Imagine, for example, someone blowing a cigarette smoke cloud in a room. Now, imagine taking a straw and blowing into the cloud of cigarette smoke.
Do you blow a hole through the cloud equal to the diameter of the straw? No. Instead, your breath coming out of the straw expands in every direction and blows a sort of clean-air bubble in the cloud. And as you blow a clean bubble into the cloud, the clean air you're blowing also siphons smoke from behind you and starts to blow that along with the clean air bubble, and after a breath or two, you're just mixing the smoke with the clean air.
Likewise, as soon as air enters the separator and is no longer constrained by the inlet, it fans out in every direction, looking for the path of least resistance. As soon as the airstream finds a slot, it wants to move through that slot (where the resistance is lower) and mix with whatever is there.
So we need to focus it, make the air do what we want it to do. If the slot is too soon, the fast moving air will siphon debris, just like our straw did with the smoke. So we want to give the air a chance to expand a bit, and slow down, before showing it the slot. Once the airstream has spread-out and slowed-down, we have a slot, and we allow the slowing air with debris to expand into the slot. As it comes around full circle, we want to take the slot (and any debris down below) away and direct the now clean air to the outlet tube.
Just think through that when you're doing your experiments. There may be a better way to do it, but I sure haven't found it.
Good luck and post-back some pictures when you come up with something.
thats a very good analogy phil
it explains the solid part of the slt very well . i never thought about it like that.
I do understand that your construction is not a cyclone. Your construction allows the air to slow down and expand a bit, so that the debris has time to sink into the slot. This is a sound idea. But as you say, with the inlet close to the baffle, there will inevitably be some turbulence there. So the baffle needs a solid part that hinders the turbulence from influencing the air mass (and debris) below the aperture to re-enter the air flow above the baffle.
But the Virvelvind is a (short) cyclone, that tries to keep airspeed as high as possible, pressing the dust out to the outer wall. This is why a stepped construction might work without a big baffle. The inlet is, relatively speaking, far from the step (and vortex breaker). The inventor talks about airspeeds of 180 km/h (50 m/s or 110 mph) in the cyclone. I don't know about that, but the idea behind a cyclone is just that: high airspeed.
The lower part of the cyclone ("above the fill line") allows the air to slow down and expand a bit. Therefore, I was thinking that your baffle might help. But you seem to be saying no.
Anyhow, since people seem to be happy with the performance, I'll risk it and buy one. Given some time I'll experiment with it too.
Quote from: jalar on January 17, 2013, 01:22:32 PM
I do understand that your construction is not a cyclone.
They're both technically centrifugal separators, they could be referred to as cyclonic separators. But neither the VV or my design is really a "cyclone," I suppose, as that term is used in industry and typically refers to a more conventional unit featuring a cone.
Agreed.
Quote from: jalar on January 17, 2013, 01:22:32 PM
I do understand that your construction is not a cyclone. Your construction allows the air to slow down and expand a bit, so that the debris has time to sink into the slot. This is a sound idea. But as you say, with the inlet close to the baffle, there will inevitably be some turbulence there. So the baffle needs a solid part that hinders the turbulence from influencing the air mass (and debris) below the aperture to re-enter the air flow above the baffle.
The turbulence isn't there because of the baffle, the baffle is there because of the turbulence. The turbulence exists in the VV design, too (incoming air running into an already spinning air mass causes turbulence). The designer of the VV just didn't do enough to address it (IMHO).
Spinning air masses undulate (they move in waves). Cyclonic separators are full of turbulence. They need to tame the turbulence to adequately separate.
Quote from: jalar on January 17, 2013, 01:22:32 PM
But the Virvelvind is a (short) cyclone, that tries to keep airspeed as high as possible, pressing the dust out to the outer wall. This is why a stepped construction might work without a big baffle. The inlet is, relatively speaking, far from the step (and vortex breaker). The inventor talks about airspeeds of 180 km/h (50 m/s or 110 mph) in the cyclone. I don't know about that, but the idea behind a cyclone is just that: high airspeed.
"Short cyclone" is merely a label that could just as easily be applied to my design. Calling the VV a "short cyclone" does not make it unique in any way.
Quote from: jalar on January 17, 2013, 01:22:32 PM
The lower part of the cyclone ("above the fill line") allows the air to slow down and expand a bit. Therefore, I was thinking that your baffle might help. But you seem to be saying no.
You could always try it.
Quote from: jalar on January 17, 2013, 01:22:32 PM
Anyhow, since people seem to be happy with the performance, I'll risk it and buy one. Given some time I'll experiment with it too.
Sounds good.
Do many people use them for woodworking? I wonder because I haven't come across it before.
Quote from: phil (admin) on January 17, 2013, 02:01:14 PM
The turbulence isn't there because of the baffle, the baffle is there because of the turbulence.
I agree with you on this, perhaps I was unclear in the previous comment.
Quote from: phil (admin) on January 17, 2013, 02:01:14 PM
The turbulence exists in the VV design, too (incoming air running into an already spinning air mass causes turbulence). The designer of the VV just didn't do enough to address it (IMHO).
There certainly is turbulence there too, but I think that he has put some thought into this. He went about solving this differently (IMHO).
Quote from: phil (admin) on January 17, 2013, 02:01:14 PM
"Short cyclone" is merely a label that could just as easily be applied to my design. Calling the VV a "short cyclone" does not make it unique in any way.
True. I do suspect that the airspeed is higher in the Virvelvind, though, but see below.
Quote from: phil (admin) on January 17, 2013, 02:01:14 PM
Do many people use them for woodworking? I wonder because I haven't come across it before.
No, and I think your design might be more suitable for woodworking, with large(ish) shavings and sawdust. There is a sweet spot size like you said, and that is porbably larger in your separator. Many here use the Virvelvind to protect their vacuum cleaner when they clean out ash in their wood-pellet burner. That is why I'm so focused on small-sized dust. The down side is probably a larger pressure drop (less air flow).
i take it jalar that you are swedish or in that area.
im in ireland
where can you buy this
i dont see any way on the site . i could contact them
how much is it
i could do with a seperater for ashs
I found catalog outfits in the US that sell them, do services like google/bing shopping work for you guys, maybe you can find a catalog or mail order house?
Yes, I'm in Sweden. The retailers are too far from me, I can tell from the retailer map on the swedish pages. :( For me it's probably simplest to call the manufacturer directly, but email would be an option I guess. I wonder what they charge for the transport...
i was looking for a retailer so i could see how much they wanted for it and how much to ship
it would probably be too expencive to buy and better off building one
The ash cyclone with bucket and heat resistant hose is SEK 956. Not cheap.
that seams a little high.
thats about 110 euro. plus shipping etc
aldi are selling their bucket with a moter set up. for 40 euro
it has a fire rated hose and metal bucket.
my neighbour has a broken one . i might liberate it and build my own version and see what hapens
What's a "moter"?
sorry motor
Oh, of course, silly me :D
There are industrial size ones too, see the last page of http://www.enviroheatuk.com/files/brochure%20UK.pdf (http://www.enviroheatuk.com/files/brochure%20UK.pdf). 8 inch hose and 5 feet diameter for the cyclone, yikes!