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All Replies on Building a Cyclone vs a Thien Baffle: pros and cons?

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View Kenny 's profile

Building a Cyclone vs a Thien Baffle: pros and cons?

by Kenny
posted 02-23-2012 07:50 PM


37 replies so far

View gfadvm's profile

gfadvm

14940 posts in 3498 days


#1 posted 02-24-2012 03:09 AM

Kenny, Look at my chip separator I posted recently. I was very skeptical when I built this but it performs amazingly well. I just emptied the barrel and had only a double handful of dust in the plastic bag under the DC. I have almost nothing invested in it and built it in a day. I wouldn’t mess with the more complicated cyclones or Thein baffles after building this one. Sometimes simpler is better!

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View Loren's profile

Loren

10477 posts in 4455 days


#2 posted 02-24-2012 03:14 AM

I have a cyclone I bought used from a guy who built it from
the Wood Magazine plans. It works great.

It only consumes 4 square feet of floor space. The benefit
of not fussing with a bag dust collector with its need for
headroom, the flimsy wheels and top-heavy design make
using the cyclone a real pleasure in contrast.

View kizerpea's profile

kizerpea

775 posts in 3175 days


#3 posted 02-24-2012 07:03 AM

i bought the woodmag plans an built my own. it looks nothing like the plan…plans are made to be changed or customized to your shop it,s in my projects

-- IF YOUR NOT MAKING DUST...YOU ARE COLLECTING IT! SOUTH CAROLINA.

View fussy's profile

fussy

980 posts in 3858 days


#4 posted 02-24-2012 07:49 AM

The Thein baffle works as well as, or better than a cyclone, takes up NO space if you put it in the dc ring, costs nothing, and is a 45 min-1 1/2 hour build. Next to nothing gets in my Wynn filter. Go to Thein’s site and look at what they do.

Steve

-- Steve in KY. 44 years so far with my lovely bride. Think I'll keep her.

View Patrick's profile

Patrick

39 posts in 3607 days


#5 posted 02-24-2012 08:39 AM

My DIY system is loosely based on the Thien-baffle concept. You can check it out in my project for pictures. After 6 months of use, the most sawdust I could get out of the Wynn filter was maybe 2 cups of flour. There are a ton of similar setups, most commonly adapted to the HF 2hp DC, which have worked very well for people. I believe it is easier, cheaper, requires less space, and works well enough. The cyclones also add more resistance (SP), which would especially be a consideration in a lower HP system. Good luck!

View Kenny 's profile

Kenny

260 posts in 3256 days


#6 posted 02-24-2012 08:42 AM

Fussy,
I don’t have to go anywhere but to my own shop to see and use a Thien baffle, I have one on my shop-vac, works good.
But, I’m not totally sold on the Thien yet.
And I’m especially not sold on the “in the ring” Thien, and for one main reason: it doesn’t pull out debris before it goes through the blower.
However, I do like the idea of a JET style “Vortex Cone”, and possibly with a rim around it like the Thien baffle has. BUT, only if I were also running some type of pre-blower separator to keep possibly damaging objects from making it into my blower.

It’s something I’m going to have to think about and consider for a bit, and hearing both sides and keeping an open mind is my plan for now.

Thanks

-- Kenny

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Kenny

260 posts in 3256 days


#7 posted 02-24-2012 08:46 AM

“The cyclones also add more resistance (SP), which would especially be a consideration in a lower HP system.”

Now THAT speaks volumes to me! If it is true, I would end this debate right now. I’m looking to get the most performance, not the most drag on my system.

I had thought the opposite would be true, but seeing as I know little about airflow, I could well be wrong, and I likely am.
But, it’s why I asked questions before buying something I know little about.

-- Kenny

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Patrick

39 posts in 3607 days


#8 posted 02-24-2012 09:33 AM

Check out billpentz.com for more info. It’s THE website on dust collection theory and is where I learned a ton. It’s definitely a must read.

View Fred Hargis's profile

Fred Hargis

6322 posts in 3301 days


#9 posted 02-24-2012 12:20 PM

I built the Wood cyclone and used for several years before I changed over to a commercial model. I believe the Wood worked every bit as well as the one I have now. But I did have a much larger DC hooked to it ( 2 1/2 HP, 12” Impeller) than they did in the design, enough deal with the increased drag. Almost anything you do for a separator will increase drag, some more than others. As mentioned above it has a bigger impact with a smaller DC. Check the Pentz site, start with the FAQ part since there is enough techno-bable there to give you a headache.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Loren's profile

Loren

10477 posts in 4455 days


#10 posted 02-24-2012 04:58 PM

If you are just running 1 machine at a time (no wide-belts allowed),
you can run fixed ducting all over a modest shop with blast gates
and have plenty of suck with a 1.5HP blower. Honestly, there
is no need to overthink it unless you have more than 1 port open
at a time and longer runs of duct than would be possible in a 20×20’
shop. A 1.5-2HP cyclone of regular DC will be fine for most machines
but not a wide belt sander.

View Kenny 's profile

Kenny

260 posts in 3256 days


#11 posted 02-24-2012 09:05 PM

See, thing is, I like to turn, and I turn a LOT! And that turns into a lot of sanding on the lathe, one of the hardest machines to collect dust and debris from.
My train of thought, as well a what I’ve read, says you need a lot of air to collect from a lathe, so making this little DC suck for all it’s worth is my plan.

Also, It is my thought that the more fine dust I can pull out of the air stream before it hits my filter, the better. I know and accept that I’ll never remove it all in any separator, just the facts.

However, after researching cyclones for several hours today, as well as various baffle designs, I’vE decided against the cyclone, for now anyway.
From what I’ve read, the cyclone is going to cost me a lot of flow. And after looking at a few commercial cyclones and their flow numbers (which are much lower than a comparable “standard” type collector), I feel that my 2hp DC will be far better suited to a Thien baffle.
Maybe if I had a larger impeller to help deal with the added resistance it would be worth it. But with my present DC, it just doesn’t make sense.

I think Bill Pentz is right, you need a 12” impeller and 5hp to really make it worth while and operate properly. I thought I may be able to get away with less, but it will just cost me too much performace and offset any gains I may have seen.

I’ll be building a Thien Baffle to sit atop a barrel of some sort, likely a Rubbermade Brute trashcan or a metal trashcan.

I am considering using 6” pipe into and out of the separator, as I was planning to use it for the main lines of my system anyway.

Thanks

-- Kenny

View DS's profile

DS

3521 posts in 3228 days


#12 posted 02-24-2012 09:16 PM

I keep thinking I should upgrade my stock HF DC, so this thread is very helpful to me.

The lathe dust collection sounds interesting to me. Mostly, I deal with lots and lots of chips and shavings from my lathe. My last lathe project was 7 pedistals each standing 48” tall and 14” in diameter. They were turned in 3 peices each, a base, a column and a cap.

I cut the blanks into octagons on the bandsaw to minimize the shavings, but by the end of each column I was literally up to my knees in shavings. There is a reason I own a snow shovel in an area that NEVER snows. Collecting to a DC seems almost futile, if not impossible for the lathe. I’d like to see how that one works.

-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251

View gfadvm's profile

gfadvm

14940 posts in 3498 days


#13 posted 02-25-2012 02:04 AM

Kenny, My ‘chip separator’ does not decrease my airflow any that I can determine.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View HorizontalMike's profile

HorizontalMike

7874 posts in 3722 days


#14 posted 02-25-2012 02:16 AM

Ditto gfadvm, and I could care less that my DC improves by some fraction of one percent. ALL of these things help clean the air. For the sake of argument, just quit bickering (the generic you) about who is best and choose one and be done with it. If you think money solves the problem, send the money to me. I’ll take it and compliment your choice,... yada, yada, yada,...

FWIW, my Thien separator does the same job as the Grizzly plastic separator does. I can NOT see any performance increase. The Thien MAY be cheap to build if you use scrap lumber, but only maybe. I have both.

-- HorizontalMike -- "Woodpeckers understand..."

View Kenny 's profile

Kenny

260 posts in 3256 days


#15 posted 02-25-2012 05:45 AM

Mike, I understand your point, but you’re way off on the percentage of increased flow with a the average baffle vs a cyclone. From what I have read (which was based on a lot of testing), a cyclone would cost my DC 20%+ in flow. FAR from a fraction of a percent.

As for Grizzly vs Thien, you may be right. But I’m not looking at a Grizzly, or any other commercial unit. And to be honest, I’ve owned and used a commercial bucket-top separator with my shop vac, very similar to what you pictured, only smaller. It sucked, and not in a good way. It scrubbed off dust and chips so badly that I was emptying both the vac and the bucket at the same time, and the vac would have more in it than the bucket! (full vac, 2/3 full bucket)

I built my Thien, and I have cleaned my filter once in 16 months, and that was just to set my mind at ease, it certainly didn’t need it.

The reason I asked what I did, was because I was comparing two very different systems, one I’ve never had any real experience with. I’ve had my mind made up since the get-go, if I was to build a separator, it would be another Thien. The only other thing I considered was a cyclone, as it’s a very different system that obviously works pretty well.

Don’t get me wrong, I’ve seen other separators that I think are well made and I’m sure they work well. I just know what I’ve tried, and I know what has worked for me. I was hoping for an improvement, but it looks like the Thien is where it’s at, so to speak.

I picked up my trashcan earlier tonight, along with the fittings I need and some all-thread. Circle jig is on the bandsaw, all ready to go. Just need to dig out my sheet of MDF and get cuttin!

Thanks to all who had input. Much appreciated.

Next “project”, the “Vortex Cone” to put in the ring.

-- Kenny

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Patrick

39 posts in 3607 days


#16 posted 02-25-2012 07:00 AM

I agree with Kenny. I think maybe gfadvm and horizontalmike are comparing different non-cyclone separators to each other, and they are correct in saying that their resistance is probably about the same. Cyclones, on the other hand, do have more resistance, but higher separation efficiency. I definitely agree that the trade-off is not worth the bigger size and price tag of the cyclone, which is why I went with the Thien-style separator.

Good luck Kenny!

View ScottN's profile

ScottN

262 posts in 3487 days


#17 posted 02-25-2012 02:52 PM

As someone else suggested Bill Pents has all the plans ,cut sheets. Every thing you could ever need on how to build a cyclone. http://billpentz.com/woodworking/cyclone/CyclonePlan.cfm

-- New Auburn,WI

View HorizontalMike's profile

HorizontalMike

7874 posts in 3722 days


#18 posted 02-25-2012 03:27 PM

Kenny, please understand that I truly mean the “generic you” and not you personally.

This topic has popped up frequently on LJs, aka ad nauseum, and everyone has the ‘best’ solution. They all work and they all work rather well. Well enough to protect your health/lungs.

I built a rather crappy looking Thien separator and would have rebuilt a ‘better’ one IF, and that is a big IF, the one I built did not work so well. There are many more things that can/do detract from the DC and that is total length of run, hose diameter, flex vs rigid, how many machines used at once, how many blast gates, etc. And it is MY opinion that, more often than not, folks are trying to max out their typical machine’s abilities(usually an HF DC), instead of living comfortably within said machine’s ratings. Those who can afford more capacity usually don’t worry so much about home remedies, as far as I have noticed.

Personally, I choose to live within the machine’s limitations. My HF DC w/separator works with ONE 10ft flex section on my TS, BS, Jointer, and it works with TWO 10ft flex hose length on my Planer and Horizontal Mortising Machine. I have a dedicated shopvac w/hepa+separator for my mitersaw. I have never needed more suction/capacity. The minor inconvenience has been well worth the gained efficiency of moving the hose from machine to machine, IMO.

-- HorizontalMike -- "Woodpeckers understand..."

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Kenny

260 posts in 3256 days


#19 posted 02-25-2012 04:40 PM

No offense taken there Mike! I’m new here and I haven’t had the best luck with the search function. I tried searching a few times for this, and after not finding the answers I wanted, I posted this.

It is my personal opinion that the Thien is one of the easiest to build and best working non-cyclone separators, hands down. And as you’ve seen, they do not in any way need to be “nice and pretty” to work very well. (you should see mine!)

I will need to run some hard-line on my system, I just don’t really have any other options. The DC is too tall to roll around my basement shop. I actually used studs where the bag support is and bolted the ring to it’s support, and then use wingnuts to remove the bag support when I need to move my DC (I only have flex right now, no hard-line yet).

So, in light of my needing to run about 30’ of hard-line, I feel I can safely do a few mods to the DC to get it back up to it’s max performance. And, it’s just in my nature to hot-rod everything I own. I understand it’s not something everyone see’s necessary (my father has been baffled by it for years), but it’s what I do.

Although, unlike some others who have done mods without really knowing if they help, I plan to actually do some reasonably accurate testing to see what helps and what hinders.

Some may see all this as more work than it’s worth and unnecessary. I, however, see it as a chance to learn about something that piques my curiosity.

-- Kenny

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Kenny

260 posts in 3256 days


#20 posted 02-25-2012 04:51 PM

ScottN,
The cyclone plans on Bill Pentz’s site are for a complete cyclone system in which you construct the blower housing as part of the cyclone housing, as pictured here:

This is not what I am looking for and wouldn’t have worked in my application, as I plan to retain the blower housing and filter bag assembly on my Harbor Freight DC unit.
You also must purchase the “ClearVue Cyclone” to build the system, which creates another issue for me: it is too tall to even fit in my shop, never mind the issue of pricing!

What I was looking at from Cyclone Central, was a lot smaller than the ClearVue. More along the lines of a over-sized Oneida Dust Deputy.

My wish was to find something I could plumb in ahead of the blower on my DC and use atop a trash can as a pre-blower separator, much as the Thien Baffle is used.

Thanks for the link though, I do appreciate the thought.

-- Kenny

View HorizontalMike's profile

HorizontalMike

7874 posts in 3722 days


#21 posted 02-25-2012 05:17 PM

Kenny,
FWIW, I actually leave the DC & separator parked in one central location against the wall. Only the machine end of the hose gets moved. In the image below, you can see the DC on the left and how easy it is to get to the TS, BS, and Jointer with a single length of hose. The planer would be closer to where I stood to take the picture and requires the longer hose.

-- HorizontalMike -- "Woodpeckers understand..."

View Kenny 's profile

Kenny

260 posts in 3256 days


#22 posted 02-25-2012 05:40 PM

Man oh man, would I love to have a nice open floor plan like you have Mike! That is a nice shop! Really nice! And that’s a nice bike off to the right too! (H-D I take it?)

Where my house is old (built in the 1920’s or 30’s), the ceiling (or floor joists) are rather low, maybe 7’, and there is a bunch of stuff that breaks up the space in less than ideal ways. I’ve got 2 big cedar tree trunk supports in the middle of the floor, the stairs that come down are smack in the middle, the furnace and chimney are in the middle of the floor, and then I have the water heater, oil tank, an old metal sink with cabinets and drawers below it (that is handy though, water in the shop is key!).

There is just no real way I could run flex everywhere, there is just way too much in the way. Even running hard-line is going to be a major challenge with all the water lines for the heat and running water upstairs.

But, it’s what I have, and I’ve got to do the best I can with what’s there. I’m thinking a major reorganizing project is in order!

-- Kenny

View DS's profile

DS

3521 posts in 3228 days


#23 posted 02-27-2012 05:28 PM

Is this the same unit as the Grizzly one Mike pictured?

-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251

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brtech

1068 posts in 3730 days


#24 posted 02-27-2012 05:58 PM

Has anyone done an actual test of the resistance of a Thien baffle? I haven’t, but it seems hard to believe it’s not at least in the same range as a well designed cyclone.

I mean, I understand that lots of users find it doesn’t SEEM to affect airflow, but it’s pretty hard to detect a 20% change without an actual measurement.

I think, with no data, that a well designed cyclone will affect airflow less than a Thien, but I don’t know for sure.

The difference is the size, expense, and difficulty of construction. The Thien wins, hands down.

View Patrick's profile

Patrick

39 posts in 3607 days


#25 posted 02-27-2012 06:20 PM

Bill Pentz is the main source, as far as I know. Check out his website for more info.

Anyone please correct me if I’m wrong, but this is my understanding of the theory behind dust separators:

The whole point of a cyclone is that it separates most of the fines as well as the chips. To get this performance, a cyclone speeds up the air (less volume as the cone gets narrow means velocity increases). This increases centrifugal force, which is what sheds the particles in any type separator. This comes at a price, though, because drag increases to the square of velocity (if speed doubles, drag quadruples). So to get better separation, you need higher airspeed; to get higher airspeed you need more power (bigger fan, motor). Thien-type separators also use centrifugal force, but the straight design doesn’t speed up the air like a cyclone, thus less resistance. This is also why you should use 6” pipe instead of 4” for your ducting (much less resistance). This principle is why I chose to make my fan input pipe a cone instead of straight (there are pics of it in my project, for anyone who is interested). I thought that design would mimic a cyclone, but without the extra space required.

View Charlie's profile

Charlie

1101 posts in 3094 days


#26 posted 02-27-2012 06:31 PM

I built my shop last year, but really only started organizing and setting thigs up THIS year. I have a small Delta DC. AP400. Only used on one machine at a time ‘cause that’s all I can run at a time anyways :). While y’all are talking about Thien vs cyclone, I’m sitting here reading this and thinking…. “I’d be happy with a trash can separator right now, ‘cause I have nothing between machine and bag.”

Taking the bag off to empty it is a drudge. I’m seriously thinking about just getting the Grizzly 30 gallon can cover because it’s better than what I have now…... nothing! Even a drop box would be better than what I have now. :)

But I’m paying attention, because at some point I’d like to move the DC into an shed-like addition and get it out of the shop. So getting to the bag will be even LESS convenient.

View Kenny 's profile

Kenny

260 posts in 3256 days


#27 posted 02-27-2012 06:58 PM

It is my belief that a Thien baffle will be more efficient from a flow standpoint, simply because it keeps the incoming air in such a small space and doesn’t force it to travel nearly the length it does in a cyclone. The less distance the air has to travel, the better it’s going to flow. Add in all the velocity stuff that was stated above, and it’s easy to see why a Thien flows more.

However, I do not believe for a second that it doesn’t cost any flow, that’s simply impossible. Humans also are simply not able to detect such things without some type of measuring equipment. Even a 15% decrease in flow when dealing with the massive volume that even a Harbor Freight DC moves would be impossible for most any human to accurately detect without the aid of measuring equipment.

I will be making a manometer in an attempt to measure the flow of air with some accuracy, and hopefully I will be able to give us all an answer on whether the Thien costs us airflow, and if so, how much. Obviously I am not an expert in this field, and my testing is only subjective and will in no way be “scientifically correct”. But I hope to give us all a basic idea about how Thien baffles andother modifications effect the flow rate of our collectors.

-- Kenny

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Grandpa

3263 posts in 3483 days


#28 posted 02-27-2012 09:18 PM

At the present time I have nothing. I do have a Clear Vue that is supposed to ship today. the motor control arrived today. I feel that if a baffle were the BEST then that is what the BEST would have on them instead of a cyclone. I am not saying the baffle system doesn’t work rather I am saying they don’t work as well as a well designed cyclone system. If a $150 collector with $200 filters added and a Thien baffle added was the best then the big guys would be out of business. It doesn’t seem to be that way. The $150 system described works well but it doesn’t work best. I am still at a loss why we will spend the extra to have the best saw and not spend the money to have the best air filtration system. If good enough is what we want then we should be using saws that are good enough. Sears is back in business. Please do read the Bill Pendtz writings. This was a man with a breathing problem. He has done the work for us so the very best is available.

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HorizontalMike

7874 posts in 3722 days


#29 posted 02-27-2012 11:15 PM

DS251,
Yes, the one you linked to is the one I have hooked up to my shopvac via another 30gal can. I have tried that same unit with the HF DC and really did not see much difference other than you could not let the can get as full before emptying as you could with the Thien baffle/separator.

-- HorizontalMike -- "Woodpeckers understand..."

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DS

3521 posts in 3228 days


#30 posted 02-27-2012 11:33 PM

Thanks Mike. I am running a stock HF DC. No mods… no complaints.
Only I cringe when a good size chunk o’ wood gets sucked into the impellor and Blamo!

I’m less concerned about the efficency than I am about not destroying the thing. It never fails that my floor sweep collector manages to get all kinds of odd waste in it which ends up on the grate in front of the impellor which closes off the input. I really hate having to crack it open to get all that out of there.

I would hope a seperator might eliminate these issues.

-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251

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HorizontalMike

7874 posts in 3722 days


#31 posted 02-28-2012 12:59 AM

Indeed it does keep the big crap from blocking the impeller input port. And popping the Thien separator off the trashcan is much easier than changing out the plastic bags on the DC every time you need to empty.

-- HorizontalMike -- "Woodpeckers understand..."

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jmos

917 posts in 3177 days


#32 posted 02-28-2012 02:50 AM

Ok, here are some musing from a Chemical Engineer. It’s been a while since I’ve done much with gas handling systems, but… First, I agree data is king, and without hard data it’s all speculative. I’ve also spent some time on Bill Pentz’s site, and I think his data is pretty solid.

Anyway, both the cyclone and baffle designs work by slowing down the air flow, which allows larger particles to drop (higher velocities are required to carry larger particles), and by changing direction, and using the higher mass of the particles against them (air goes one direction and the momentum of the particle carries them in another direction).

For any system to have any effect it has to consume energy (first law of Thermo, there’s no such thing as a free lunch). In a simple DC system, with a constant speed motor, this reduces flow by increasing frictional losses (causing the blower to move less air and by making the motor work harder).

With a simple trash can lid separator the air is moving rapidly through the duct and then opens up into a much larger diameter can, greatly slowing the velocity. If baffles are present there are also changes in direction to help knock particles out of the air stream. (The air is then accelerated again as it exits the separator in its way to the impeller.) The more the velocity is reduced (bigger can), and the more direction changes, the more efficient the particle removal.

The cyclone sets up a rotational airflow which effectively is a constant change in direction (that’s what we feel as centrifugal force, which isn’t a real force at all), as well as decelerates the airflow by increasing the area. The particles keep banging into the walls, and the heavier particles will drop out of the airflow. Keep in mind the bottom of the cyclone is shaped to promote transport of the particles down to the collection bin, and clear them from the air flow, but doesn’t really effect the separation (if they were not cleared they would build up and get re-entrained in the air.) A cyclone is more aerodynamically efficient than a baffle.

Now, for the question I can’t be 100% positive of the answer of the top of my head, but I plan on researching; which is better? I hear Grandpa’s comment, and I tend to agree with him. Just looking at some advertised systems, they all put a cyclone in front of very high MERV filters. I believe that’s because the filters would load up too fast in a regular DC. I think if they could get reasonable life by adding a garbage can type first stage separation, or a vortex cone, in front of really high MERV filters (15/16) they would, as they would hit a much lower price point and sell a bunch of them.

I tend to think that if you want the best efficiency system (removal of the most, and the smallest particles) you need to go cyclone with high MERV filter. However, other changes can make improvements over the basic DC system.

-- John

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kizerpea

775 posts in 3175 days


#33 posted 02-28-2012 01:39 PM

the key to dust collection…......the amount of air u take in has to get out…fact….the sq ft of filter decides if that will happen. the more filter u have the easyer the air will flow..if the filter is to small air has to be forced through, thats when your (sp) starts to rise…..look at the size of bill p,s filter..in this case more is better.the wynn filter has around 274sq of filter. i am working on the filter for my cyclone now an should be done in a couple of weeks..my filtering system will have close to 426sq ft will post it when i,m done

-- IF YOUR NOT MAKING DUST...YOU ARE COLLECTING IT! SOUTH CAROLINA.

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HorizontalMike

7874 posts in 3722 days


#34 posted 02-28-2012 02:54 PM

I don’t have the means to test this, nor the specific knowledge, but shouldn’t any comparisons between Thien separators and cyclones BE SCALED to each other in order to have apples-to-apples (aka even playing field)? And how would one do this in the first place?

++ Square footage of the walls of the separator VS square footage the cyclone walls?

++ Volume of the separator cavity VS volume of the cyclone cavity?

Strictly my ‘guess’ here… I would imagine that an equal sized cyclone would NOT have much advantage over that of a Thien separator of the same size/volume. Every cyclone I have seen seems to be much larger than the Thien separators they are compared against (only exception are those tiny cyclones I see on 5gal buckets).

-- HorizontalMike -- "Woodpeckers understand..."

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Patrick

39 posts in 3607 days


#35 posted 02-28-2012 03:12 PM

“I know the Thien baffle is a very popular and low-cost separator, and I know it works rather well from experience. But, now that I have upgraded to a true DC from a shop-vac, I’m wondering if it may be worth the effort to put together a true cyclone.”

It’s so easy to get into a discussion about all the different possibilities and arguments of dust collection. I think you have to look at the whole picture and be practical. If you read the original post, he wants advice on whether to build a cyclone or a Thien-type system. For me – and due to the popularity of the Thien baffle, I suspect a lot of people – I think you can get very good results, in terms of dust collection, particle separation and thus filter cleaning, at a fraction of the cost and size of a true cyclone system. Nobody disagrees that cyclones are better (they at least separate better), but if a HF 2hp DC and a Thien baffle cost under $300 and a cyclone costs double or triple that, and each setup can go several months or longer between filter cleanings, I think most people would choose the Thien. (In all fairness, I am assuming that Bill Pentz’s data is correct and cyclones require much more power and a bigger fan in order to overcome the higher resistance and maintain similar flow. This is what would make a cyclone so much more expensive) If money and ceiling height isn’t a problem and you want the best of the best, by all means go buy or build a cyclone. In my experience over the past 6 months of operation, the Thien works great. I only got about 2 cups of flour out of the filter after 6 months, and I’d be surprised if you didn’t get similar results from a cyclone. Also, regardless of which system you choose, be aware that you will still need to wear a dust mask sometimes because you’re never going to be able to get everything.

Most importantly, have fun!

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Kenny

260 posts in 3256 days


#36 posted 02-28-2012 10:22 PM

Mike,

I understand your reasoning behind “scaling” the Thien and the cyclone to be the same size.

However, this is not the correct way to find if one has more resistance over the other in use.
To find which unit provides the least dop in flow, you would need to test them exactly as each would be used in the specified application, which in this case would be ahead of the blower on a HF 2hp DC.

Since most of us who build these Thien baffles attach them to the top of either a Rubbermaid Brute 32 gallon trash can, or atop a similarly sized steel trash can or even various plastic and steel drums of similar size, this is what you would want to install the baffle on for testing, as this is how it will actually be used.

Using a massive container with the internal baffle area enlarged enough to be scaled to equal a cyclone would simply not give you any applicable data, as this is not how the system would be configured for actual use in a general home woodshop scenario.

I hope this makes sense!

-- Kenny

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HorizontalMike

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#37 posted 02-29-2012 03:49 PM

Kenny,
Yes and no. My point is that most of these cyclones are much larger than the Thien separators.

I can see equalizing the DC units, but why stop there? The size of the separator and cyclone should match as well. After all, drag racing a Corvette against a VW Bug is not an exercise in equality, EVEN THOUGH they are both individually designed to go down the same road and transport you from point A to point B. All variables need to be accounted for, not just select variables just because of a matter of convenience.

FWIW, we will probably never see an equal head-to-head comparison of cyclone vs Thien separator because those involved don’t really have the need or inclination to do so. I would imagine that some mathematical equalization/comparison could be made though I would suspect that aerodynamic flow may change due size alone, but just guessing here.

-- HorizontalMike -- "Woodpeckers understand..."

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