As stated, I have the Jet Air cleaner on the ceiling, but I came across this video and plan to make something similar to downdraft the ambient air through a filter.
Yes, and it probably delivers that. You're comparing apples to oranges in this case, comparing the Oneida/Clear Vue 2 stage cyclones to 1 stage dust collectors. The difference is that the 1 stage collectors don't have the additional throttling that comes from running the air through the cyclone separator. Adding the cyclone, or a thien baffle, cuts down on the throughput of the machine considerably, sometimes as much as 50%. http://www.jpthien.com/smf/index.php?topic=1241.0
Take a look at the CFM for the cyclones, and compare them against similar models. Here is the grizzly G0441, claiming 3 HP, and 1654 CFM @ 2.0" SP. Compare with the Oneida 3 HP Gorilla with "1,340 Actual CFM". I suspect that Grizzly has a higher flow rate because it has a slightly larger filter, a 8" intake for the Grizzly vs 7" for the Oneida, and the Grizzly is not HEPA.
Also the Grizzly G0442, 5 HP Cyclone claims 2184 CFM @ 1.9" SP vs 2150 @ 2" SP for Oneida 5 HP High Vacuum. The Clear Vue MAX has similar numbers, hitting 1900 CFM @2" SP on an 8" inlet.
So when you compare cyclones to cyclones, I'm not seeing much difference in the numbers. You'll also note that the cyclones generally have worse CFM flow rates than the single stage collectors, given a similar sized motor, and impeller, across a manufacturer's line.
^ Another factor might simply be bad design:
CFM is dependent on the ducting, the inlet size, the impeller size, and the impeller rpm.
As we all know, HP has no effect, unless there isn't enough HP to keep the impeller at full speed, for a given system.
So, manufacturers are probably vastly underpowering a larger impeller with that 2 HP motor, in order to get great CFM numbers with no ducting connected.
Those systems probably scream in pain under real-world conditions, and probably don't last very long.
I was more or less referring to the typical single stage DC systems that you see under the tool brands that are common relative to "mass market" and are sold at retailers like you mention, but there are a bunch of "compact, short cone cyclones" that have sorta come into that space now, too. Historically, it's been difficult or impossible to get fan curves on these machines, unlike with the DC specialty companies.
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The most expensive tool is the one you buy "cheaply" and often...
Okay, but what would a fan curve mean for a system that is not designed to be hooked up to a permanent ducting system, and subject to significant static pressure? To be frank, I don't see a fan curve for the Jet or Powermatic single stage DC systems either. Yet those numbers don't seem to be in question. So this seems to be a matter of the system not being rated to do something, any more than my honda accord has a rating for how big a trailer it can pull. This doesn't necessarily mean that the numbers themselves are bad or inflated.
Also I just checked, and Grizzly provides the fan curves for their "compact short cone cyclones", models G0860, G861, and G0862. You can see them on page 34 of the manual. The numbers presented don't see too out of line with other manufacturers cyclones, so I don't think it's a matter of rebadged clones either.
FWIW, I looked at these short cone cyclones, and watched Matt Cremona talk about his Laguna, and it seems the main problem with these models is the shorts cone doesn't separate as well. Otherwise they appear to have the motors and impellers of the "tall" cyclones.
Sorry, that's not what's published by the major cyclone manufacturers, who put out performance information with the fan and motor in the context of the cyclone or whatever else is included in the system. At least that's what I've seen from Clear Vue, Grizzly, and Oneida. Since the static pressure of a single stage collector is not going to change, unless you add things like after market filters, and they're not really designed to be attached to ducting, there is a single number, with the implied static pressure of the system as a whole.
Which is not to say they can't be attached to ducting, obviously they can, but the design is to be transported from place to place, and hooked directly to the system they're being used with.
Frank is correct...the fan curve is to understand what to expect from a system under various loads. While you are "generally" correct that many/most of the single stage DCs were not "designed" to be connected to duct work, they are still marketed/show than way by folks selling them and are used that way by folks buying them. I do not believe you are accurate that the static pressure isn't going to change with a single stage system...the load in front of the system matters in real world use.
Discussions like this one are the result...folks trying to help others maximize performance or at least set expectations. There are (without trying to count) hundreds of threads on this subject here over the years at SMC alone.
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The most expensive tool is the one you buy "cheaply" and often...
Let me bottom line it for you. I don't see a fan curve for any single stage DC. I don't know why that is, expections for usage are my explaination, what's yours?
Or do you you know of a fan curve for a single stage DC?
Finally, since I'm not aware of any fan curves for and single stage DCs, why are some numbers, Jet/Powermatic, seen as reasonable, but others, Grizzly/Busy Bee, not? Because the rationale that there is no fan curve, and therefore the numbers aren't accurate doesn't seem to hold up.
I could totally see making an argument that Busy Bee, Harbor Freight, Grizzly etc have a reputation for inflating their numbers, but that doesn't necessarily appear to be the case here, or at least there's been no rationale give, or sources showing that Busy Bee claimed X, but testing showed Y. If that is the case, I'd be interested to see it. Otherwise I think everybody here is just guessing.
If you can find out the diameter and design of the impeller, you can get pretty close to guessing the fan curve. A forward curved blade like some HF collectors use will give higher readings at lower pressure but fall off more quickly than a BC blade. A straight blade will deliver less cfm at low pressure but more at high pressure. Any direct to bag machine will have higher cfm than a cyclone with the same impeller due to the pressure drop of the cyclone. The key is to identify the impeller size and shape.
Slightly OT, but since I'm already contemplating getting a larger / more powerful unit, the thing I REALLY don't understand is:
How can having too LARGE a ducting cause a motor to overheat? I've read this numerous times, but shouldn't it be exactly the opposite?
I understand the simple concept that too large a ducting might cause the cfm to drop lower than ideal (inside the ducting itself) but why would a fixed-speed motor run hot with LESS resistance on the impeller?
Fans are a funny thing and it goes counter to conventional thinking. When fan is blocked off, it can't do any work & it just speeds up. the faster it goes, the less the motor is working. So if you run a blower wide open, that is intended to work in a complete system, then the motor will slow down & work harder because it is moving more air.
Maybe someone else can provide a more eloquent explanation for this.
Basically with less air to push, the motor actually works less, draws less current, creates less heat.
https://www.wired.com/2017/03/got-so...-time-physics/
That having been said, I don't think you can necessarily take this to the conclusion that the motor will burn up with a large duct. I would suspect that the impeller housing and intake would be a bigger limitation on air flow than ducting.