Oneida Dust Cobra?

[grbmds]

Greg,

Did I understand you to say that the Cobra handles the chips from your planer? Is the planer a 13" (or 12")? Given the Cobra only has a 2 1/2" inlet with a 2 1/2" hose and maybe 250 cfm I wouldn't think this would work and would clog up. That is great performance for that size inlet and cfm.

As to the Oneida V3000, I'm sure that does a great job. It's a 3HP motor that they allege is rated at 1349cfm (and their ratings are usually accurate and are true in actual use). Even the V1500 is superior and easier for a home shoot to use since it doesn't require 220V power but it still is meant for use with a duct system.

 

[Qwerty_Adelaida]

Greg thanks a lot.

It seems like with that extra air flow Dust Cobra it gains more "power" even with less vacuum force.

I'll talk to Oneida one more time tomorrow.

 

[jacko9]

Greg,

Did I understand you to say that the Cobra handles the chips from your planer? Is the planer a 13" (or 12")? Given the Cobra only has a 2 1/2" inlet with a 2 1/2" hose and maybe 250 cfm I wouldn't think this would work and would clog up. That is great performance for that size inlet and cfm.

As to the Oneida V3000, I'm sure that does a great job. It's a 3HP motor that they allege is rated at 1349cfm (and their ratings are usually accurate and are true in actual use). Even the V1500 is superior and easier for a home shoot to use since it doesn't require 220V power but it still is meant for use with a duct system.

Since my Powermatic 100 12" planer didn't come with a dust chute (I didn't buy the option) I made a port with a 4" outlet to my 5" flex hose going to my V-3000 located right next to my planer.  The 4" restriction allowed a lot of chips and some dust to escape.  I purchased the 6" x 6" hood from Oneida and had it welded to a manifold on my planer and I no longer have any chips/dust escaping.

I have long runs to my Jointer and my Table saw and the system handles them all with the blast gates open and my shop is a whole lot cleaner.

Jack

 

[Bohdan]

I have just had a conversation with Festool and their 26/36/48 units have 96" of water column lift however they were not able to explain the diameter of water column lifted. (But neither did Oneida). So I am assuming 70" vs. 96" is not an apples to apples comparison.

The diameter of water column is not relevant as it is a reading of vacuum pressure.
Approximately 30' of water column corresponds to 1 atmosphere or about 15psi.

This reading is generally a max static pressure reading, the hose is blocked there is no airflow, and so gives little information about its performance in collecting dust but tells you that you can use longer or smaller hoses to achieve the same results.

 

[Qwerty_Adelaida]

The diameter of water column is not relevant as it is a reading of vacuum pressure.
Approximately 30' of water column corresponds to 1 atmosphere or about 15psi.

This reading is generally a max static pressure reading, the hose is blocked there is no airflow, and so gives little information about its performance in collecting dust but tells you that you can use longer or smaller hoses to achieve the same results.

Am I understanding this correctly? CFM is the main characteristic of dust/chip lifting.
The bigger the water column reading means that the smaller hose (opening) can be used to achieve same air flow (varying from maximum opening at which the CFM test was performed)?
So the system with 1500 CFM at 6" outlet will produce much less cfm if the opening is blocked either by a narrower hose or by the tool itself because its water column reading is only couple of inches. And so the motor won't be able to build enough pressure to suck extra air through smaller opening.

With that in mind
Dust Cobra is designed for 245 CFM at 2.5" opening @23" SP (what could that mean?). While Festool is 137 CFM for 2" (without any [member=2645]SP[/member] conventionalities, who needs those ).

Would be really interesting to know what CFM Cobra shows with 2" hose and vice versa Festool with 2.5" opening.

As well would be nice to have some sort of graphic for each dust separator (especially those huge cyclones with ducts) showing relationship between CFM and the size of opening. Coming from say 0.78 square inch opening all the way to 28 (roughly from 1" to 6" diameter hoses).

That kind of graph would put all the performance questions to bed.

In my application the router pressure foot actually has 2" port but we are using 2.5" hose from Ridgid vac that delivers 179 CFM (at 2.5"). Ridgid does not seem to have water column reading available, so hard to tell what happens at 2". Also the filter is getting clogged a lot which decreases CFM and the filtration is none HEPA. And even while the port on the router pressure foot is 2" the blast gates on the bottom, that allow outside air to be sucked inside, seem to have even less open surface area.

So knowing what happens when the opening is further reduced would be of great value.
It might be that due to higher water column index Festool will outperform the Cobra at 1 1/5" hose or similar surface area opening.

Hard to believe that there is no proper comparison scale between such an expensive machines. Kind of like comparing cars using just raw horsepower.

 

[Qwerty_Adelaida]

It would also be really useful to know how much CFM around an object (with mass and surface area) is required to lift it into the hose.

 

[Bohdan]

It would also be really useful to know how much CFM around an object (with mass and surface area) is required to lift it into the hose.

Its not the CFM its the velocity. The CFM and the opening size is what is required to maintain the velocity that's why a vacuum will only pick up close to the nozzle but as soon as you back away it wont pickup. To maintain dust flow in a certain size pipe a certain CFM is required, drop below that value and the dust drops to the floor of the pipe.

Pickup or capture of dust is a really complex condition which cannot be described by a singe number.

 

[gnlman]

Hi. Well let me clarify the planer statement....
I have a dewalt 735 planer that has chip ejection, and have not had a chance to use it much. When I unpacked the planer I decided to give the cobra a go to see how it would manage the larger chips. I ran a 2 x 3/4 piece of birch thru the planer and took the piece down to 1/2 inch just to test the planer....I also in my great (and stupid) wisdom decided to see how much actual chips were coming out of the planer by taking off the hose to the cobra for one run.....big mistake....had to get out the heavy duty leaf blower and spent half hour cleaning out my shop..lolol
So to be clear, the cobra had a 20 foot 2.5 inch hose attached to the planer and kept up just fine with no clogging...but the planer has a fan that ejects the chips...there was very little dust on the table, and no visible dust in the air...other planers may act differently....
I will not have time tonight, but will find some time in the morning to do some testing with different size hoses on the ct and also try it with the dust deputy ect and hopefully give you some more good data to help with your decision....this dust collection stuff is a bit mind boggling, and when you are playing with that kind of cash it's a hard choice to make....I took a leap of faith after talking to Oneida and as there was no dealer near me, ordered the cobra online....I've been more than happy as have others in my decision, and Oneida's advice played a part in helping me decide...they just didn't sell me anything, but helped me get what I needed...
I also think that the air the foot on your machine is allowing in, will help in the dust collection area.....you need to have an inlet of sorts to have a good outlet.....or in other words, you can't have everything on the machine sealed up tight as you need airflow to assist in suction, so the airspace around the foot on your cnc will assist in collection....if that makes sense..lol

 

[Qwerty_Adelaida]

Its not the CFM its the velocity. The CFM and the opening size is what is required to maintain the velocity that's why a vacuum will only pick up close to the nozzle but as soon as you back away it wont pickup. To maintain dust flow in a certain size pipe a certain CFM is required, drop below that value and the dust drops to the floor of the pipe.

Pickup or capture of dust is a really complex condition which cannot be described by a singe number.

And is there any way to measure an air velocity at the surface under the hose depending on cfm through the house opening and height of the opening above the surface? I would assume that velocity inside none obstructed hose should be constant and correlated with CFM.

 

[gnlman]

hmmm one more thing that may help you understand velocity qwerty...
I am a festool guy.
One thing the Cobra won't do is allow me to use my festool sanders...there is just too much suction....that is where the ct shines....it allows you to turn down the suction (velocity) so the sanders do not stick to your workpiece, or bounce around like crazy with you are trying to smooth a surface....
So in a test to see if I could lessen the suction of the Cobra, I tried a 27mm hose attached to around 10 feet of 2.5 inch hose to see if that would cut the velocity and suction of the cobra down enough so I could use a sander with the cobra.....no dice....it still had far too much velocity/suction for the sanders....to be honest, I bought the hose kit with the cobra, the 2.5 inch hose is 20 or 25 feet long, and I know this defies all laws of physics, but I notice no difference in suction even with a hose that long.....if I remember tomorrow I will try a comparison of this as well...
Too bad we didn't live close to each other, you could give it a try.
Greg.

 

[Qwerty_Adelaida]

I also think that the air the foot on your machine is allowing in, will help in the dust collection area.....you need to have an inlet of sorts to have a good outlet.....or in other words, you can't have everything on the machine sealed up tight as you need airflow to assist in suction, so the airspace around the foot on your cnc will assist in collection....if that makes sense..lol

Yep, it would not work at all with that gate closed, but I think that even in fully open stance the surface area is less than that of a 2" hose. So maybe Festool will produce better airflow as it is rated for narrower hose and also has larger water column index which should help to maintain cfm with smaller opening.

If you have spare minutes take a look what you Cobra does with smaller diameter Festool hose.

Hope I will be able to explain everything I learned today to Oneida tomorrow. I think the guy is already tired of me. I will now feel sorry if I decide to go Festool.  

Thanks for everyone's input.

 

[Bohdan]

If you have air traveling at (as an example) 1000'/min and your router spits out the chips at 1500'/min then the chips will only slow to 500'/min and not be captured. If you have a shroud around the cutter that the chips hit and bounce back then they will be captured and collected. The shroud can be solid like on the Festool routers which raises the air velocity in the opening to catch the chips or a brush curtain which catches the chips and is what I think is normally used on CNC routers

As the air velocity reduces exponentially from the opening the smaller the shroud and the closer to the pipe the higher the velocity and the better the collection. However you must have a big enough total opening to allow the system CFM to flow.

This is why the Festool extractors work so well, the high suction enables the opening to be kept small and the velocity high.

 

[grbmds]

Confused a little now. . .The Oneida Mini Dust Gorilla (which is portable and has 5" inlet and is designed to use a 5" diameter 10' hose) is spec'd at 600cfm. In the table that is on their website, the data implies that the velocity would be about 4500 fpm. My history with dust collectors for planers, jointers, bandsaws, even table saws indicates that it is important to have a larger opening regardless of chip ejectors (and I also have the Dewalt planer and have used it for years). To me, it's amazing that the 2 1/2" Cobra could pull that kind of volume of chips.

I swear by Oneida, their support, and their assistance in buying, using, and designing dust collection systems, but I'm confused and trying to make sense of this so I don't end up upgrading my system with something that might not be best in the long-run.

My past information indicates that you really need around 400+ or so cfm to handle planers, jointers, etc.; the bigger tools that put out a lot of chips and dust. Those usually have at least 4" openings.

 

[JayStPeter]

The fans on different machines are not linear.  They work best at a specific volume of air and static pressure.  So you need a different fan to pull volume through a 2" hose than you do to pull air through a 4" hose.  When you neck down a 3HP Dust Gorilla to 2", you aren't giving it sufficient volume (raising static pressure) for the fan to be efficient and it doesn't flow the same CFM anymore.  If you hook a shop vac to a 15" planer with a 4" port, the air volume is too much and the fan doesn't pull as much air as it did with higher static pressure of a 2" hose.  You're looking at one number on the fan curve to make your comparison and not at the entire fan curve.  I hope that makes some sort of sense.

 

[Bohdan]

If you really want to get confused about dust collection as distinct from chip collection and all of the requirements have a read of "Cyclone and Dust Collection Research" by Bill Pentz.

http://billpentz.com/woodworking/cyclone/index.cfm

He explains all of the various considerations when designing an exhaust system to suit a workshop.

 

[gnlman]

Hi Yury. Here is the info as promised. Fog seemed to be down today, so sorry for the delay.
My own test instrument does not do CFM, and I borrowed one for my past data. I did this in ft/min which should still give you an idea of the differences. I did all tests with 15 foot hoses to try and keep the already rough data somewhat the same. I held the instrument one inch away from the ends of the hose while I measured. Hope this helps you in your decision making process….dust collection is a large and tough subject, but others on this thread are giving you very good advice, I’m just giving you a bit of real world non technical data. I don’t have a dust meter, but will tell you I find very little dust with either machine. Also, I do believe that Oneida has an “improved” Dust Deputy designed especially for the Festool  extractors, that addresses the static issue, but you may want to discuss that with them. If you are thinking of buying into the Festool system for woodworking, the extractors (ct’s) are a must in my opinion. I got by for a while with a shopvac/dust deputy setup, but the extractor works much better and keeps the air much cleaner.
Regards, Greg.

CT-36
36mm hose – 1790
27mm hose – 1070
2.5 inch hose – 2120

CT – 36 (with Dust Deputy)
36mm hose – 1350
27mm hose – 855
2.5 inch hose – 1585

DUST DEPUTY BY ITSELF MEASURED AT INLET OF CYCLONE INLINE WITH CT-36
1750

ONEIDA COBRA
36 mm hose – 1720
27mm hose – 925
2.5 inch hose - 2860

 

[jacko9]

I think the tests show that the hose size is the biggest flow restriction so, whatever system you choose use the largest hose you can with that system.

Jack

 

[grbmds]

It appears to me that, when your outlet on the tool itself is also going to be a limiting factor. For example, if you have a 2 1/2" outlet on a small table saw, that will restrict air movement no matter what the inlet or ducting is from the collector. Also, I've used my CT48 on my Incra table with an under table box. The outlet from the box is 4" and the Festool hose, 50mm, is about 2". That doesn't work nearly as well as connecting it to a 4" drop from my dust collector. So, it appears to me that the outlet and the ducting must, to some degree, match or be close to generate the maximum collection possible. Does that make sense?

 

[Qwerty_Adelaida]

CT-36
36mm hose – 1790
27mm hose – 1070
2.5 inch hose – 2120

CT – 36 (with Dust Deputy)
36mm hose – 1350
27mm hose 855
2.5 inch hose – 1585

DUST DEPUTY BY ITSELF MEASURED AT INLET OF CYCLONE INLINE WITH CT-36
1750

ONEIDA COBRA
36 mm hose – 1720
27mm hose – 925
2.5 inch hose - 2860

The thread stopped sending me notifications.
Thanks a lot for the data.

The dust deputy lowers the efficiency significantly.
I think I'll give the Cobra a try. I do not think that changing bags all the time on Festool is very convenient and Cobra seems the only way to go 2-stage without sacrificing suction.

I'll make a post when I get it.

What is the tool you was measuring your air flow with?

 

[gnlman]

Hi. No problem, you are welcome.
I used a fairly inexpensive anemometer I believe it's made by General. I bought it to do comparisons in my dust collection.

Yes that is why I went with the cobra, as introducing the Dust Deputy reduced the cfm....having said that, if you are just looking at collection from your cnc, you might try the Dust Deputy as it may still have enough cfm to keep the table clean...you could always return it if it does not meet you needs.( it also keeps your filters and shopvac clean) I used the Dust Deputy/shopvac with my track saw, routers, chopsaw, and it worked fine....I upgraded once I bought a router table and small table saw, plus a small dust collection network.....that's when I found it could not keep up....one tool at a time it was fine....Just a thought that might save you some money. Also used a auto switch with both the shopvac system, and the cobra so it's tool activated which is really handy.

Good luck and let us know how you make out.
Greg