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Thread: a new take on dust extraction
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4th March 2018, 08:49 AM #16GOLD MEMBER
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Just had a quick look on the Harvey website and the spec sheet. They claim a max 1110cfm with a 6" hose (no associated static pressure drop though) and 700cfm through a 4" hose and 5 5/8" static pressure drop. The system is variable speed like the newer Oneidas, varying the fan rpm to keep airflow maximised for a 2HP motor. The numbers don't seem great but certainly better than a typical 2HP dustie, with much better filtration and much quieter.
It could be a good system if they upped the fan size and motor rating.
Cheers, Dom
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4th March 2018, 10:20 AM #17GOLD MEMBER
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Hence my question as to where the 765cfm figure came from??
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4th March 2018, 11:18 AM #18.
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From WoodPixels link above leading to Gyro Air - Dust Collection - Tools - Bridge City Tool Works
Here is a list of the specs listed on the Bridge city
Gyroair.jpg
If the airflows have been done according to industry standards then all the flows will be too high.
What the 6" , 765 CFM looks like is flow rate which that create an air speed of 20m/s or 4000 FPM which is the accepted minimum to see sawdust in suspension.
It can do more than that which is where DomAUs figure of 1100 CFM comes from
The limit on the Gyro is the 12" impeller with a 2HP motor.
A 3P motor and a VFD running at 70Hz on a modified 2HP DC would have similar specs.
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4th March 2018, 12:51 PM #19GOLD MEMBER
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So, from the specs we have three fan curve points; 0 cfm at 18.5" W.C., 647CFM at 5.6", and 765cfm at 2.2". The max cfm of 1400cfm of the blower would be at 0" W.C. but would be above the 2HP rating of the motor IMO so isn't really relevant (unless it's some kind of magically efficient fan). The only complication is that this fan curve is not really a traditional fan curve but rather a combination of fan curves at various fan speeds due to the variable speed feature.
Cheers, Dom
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4th March 2018, 02:04 PM #20.
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A modified 6" intake 2HP/12" impeller can move a real 1100 CFM @50Hz .
At 70Hz it should then be able to move a max of 1540 CFM , so 1400 CFM is not that unreasonable.
Not that I recommend doing this to a stock 2HP DC, well not unless it is surrounded by at least a 5mm steel cage around the impeller
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4th March 2018, 02:16 PM #21GOLD MEMBER
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4th March 2018, 03:46 PM #22.
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The Clearvue cyclone component imposes ~2.5" WC back pressure, so the impeller alone will move more than 1400 CFM
The 2HP DC was just the impeller, no filter enclosure or filter and no ducting.
When the needlefelt filter is added it dropped to ~850 CFM, with a PF it's around 920CFM - shows that its fan curve is not that flash.
A short length of ducting and a few junctions drops the flow even further.
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4th March 2018, 09:55 PM #23New Member
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Before coming across this thread I had been doing a little reading up on the GyroAir. I picked up a glossy brochure for it from the Sydney Wood Show last year where I was most impressed by its quiet operation, and a little frustrated there was no-one available who could explain anything about it to me other than quoting the brochure.
As an aside, I've read up on on ClearVues and agree with the widely held view of this forum that in terms of performance they're very good. Noise is the one thing holding me back from buying one. (I am in rented accommodation and have neighbours directly above through a wooden floor/ceiling and to both sides of a 3.6m wide room through masonry walls. There is no option for locating (or venting) anything outside, and building a freestanding self contained sound proof enclosure is not the most appealing proposition But I digress...
In reading up on the GyroAir there are a range of performance measures quoted, but no single website quotes all of them, including the manufacturer. I've compiled a short summary below. In addition to the inconsistent use of measurement units (the GyroAir brochure I picked up at the Sydney Wood Show is the only source to quote both metric and imperial for everything), there appear to be a couple of inconsistencies in the actual values quoted on some sites, which may help explain some of the measurements quoted in this thread.
Max blower airflow - Bridge City and Major Woodworking (Australian distributor) both quote 2380 m3h (~1400 cfm)
Max airflow - GyroAir Brochure and Harvey website quote 1110 cfm. Major Woodworking quotes 1100 m3h - maybe they got the units wrong and rounded to nearest hundred?
Max static pressure - GyroAir brochure, Harvey website, Bridge City, and Major Woodworking all quote 18.5" or the metric equivalent 4600 Pa.
Max airflow @ 6" - Bridge City quotes 1300 m3h (~765 cfm)
Static pressure @ 6" - Bridge City quotes 550 Pa (~2.2")
Max velocity @ 6" - Bridge City quotes 20.5 m/s
Max airflow @ 4" - Brochure and Harvey website quote 700 cfm (~1190 m3h). Bridge City quotes 1100 cfm which equates to 647 cfm.
Static pressure @ 4" - Brochure, Harvey website and Bridge City all quote 5 5/8" and/or the metric equivalent of 1400 Pa.
Max velocity @ 4" - Bridge City and Major Woodworking quote 38.9 m/s.
Separation efficiency before filtration - Brochure and Harvey website quote 99.9%, Bridge City and Major Woodworking quote 99.7%.
Thank you all for your contributions to this and other threads, from a grateful learner.
Bye from elpablo
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5th March 2018, 06:09 AM #24Member
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It seems clear from this discussion that the GyroAir is not going to improve on a CV when running 6 inch ducting. But in some cases 6 inch inlets at the tool/machine are just not possible e.g. a ROS or some thicknessers. So if you really have to reduce down to 4 inch or less then perhaps something like the GyroAir with its higher static pressure is the best way to overcome that. Still a very expensive way to address the problem though.
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5th March 2018, 09:50 AM #25.
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A high static pressure is great to have but I'm pretty certain that on the gyro air that is before the two cyclones are at work. Those cyclones are small and according to BP they will each consume around 4.5" of WC.
The 18" of WC will thus be reduce to 9" of WC which is a whole 1" WC more than the pressures generated by a 2HP DC with clean bags.
Of course the big advantage of any cyclone is that it should maintain these pressures as there are not filter bags to get s clogged.
I struggle to believe the 4" flow figure quoted by Gyro because a duct running at those flows will be screaming like a banshee and emitting considerably more than 61dB.
A 6" duct terminated by BMH, pulling about 1000 CFM, generates about 72dB at 3m. A 4" duct pulling 425 CFM emits about 76 dB. I once managed to generate 490 CFM through a 4" duct and it was considerably louder again.
Getting back to power tools dust collection. If the power tool has a fan inside it then the flow generated by the fan and the size of the dust outlet on the tool are the air/dust flow limiting factors. High static pressure pulls very little extra flow through these fans because the air path ways through the fan are very small. Typical flows out of fan exhausted tools is in the 50 to 70 cfm range. Hence all any ducting and DC/vac has to be able to do is to deal with these small flows. On most tools with peewee size outlets and small fans, 50 mm ducting and a 2HP will suffice. Only on bigger power tools with larger fans will 3" or even 4" flexy helps.
On tools without any fans, higher static pressure systems like vacs have a distinct advantage over DCs. The so called advantage of vacs being mobile is outweighed by the fact that most leak and many even end up making more fine dust than they collect. Best practice vac systems are ducted and have the vac located outside a shed, or enclosed in an airtight enclosure inside a shed which is then vented outside a shed.
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5th March 2018, 01:05 PM #26
Upto post 21. Good read. I'll be back
DaveTTC
The Turning Cowboy
Turning Wood Into Art
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18th March 2018, 07:41 PM #27GOLD MEMBER
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18th March 2018, 09:40 PM #28GOLD MEMBER
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Thanks for that Dom but yours has a 16" impeller, I wonder what the difference is between that and the 15". Where do you do your measurement and do you use a manometer?
CHRIS
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18th March 2018, 10:23 PM #29GOLD MEMBER
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Hi Chris,
Yeah I use a 16". Not sure what the 15" would do - less, but not sure how much less.
Yes, I use a large water U-shaped manometer I picked up a couple of years ago. I measure at the inlet to the cyclone, but theoretically it shouldn't matter where you measure when there is zero flow.
Cheers, Dom
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19th March 2018, 10:28 AM #30GOLD MEMBER
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I should get a length of clear hose and make one but I suspect the bore size will affect the result or am I wrong there. I used manometers as part of my job many years ago on a daily basis to calibrate industrial instruments, both water and mercury.
CHRIS
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