Rate of Air Flow vs Volume of Air Flow

Create a review for a woodworking tool that you are familiar with (Shopsmith brand or Non-Shopsmith) or just post your opinion on a specific tool. Head to head comparisons welcome too.

Moderators: HopefulSSer, admin

User avatar
dusty
Platinum Member
Posts: 21359
Joined: Wed Nov 22, 2006 6:52 am
Location: Tucson (Wildcat Country), Arizona

Re: Rate of Air Flow vs Volume of Air Flow

Post by dusty »

What rate of airflow should I expect to see?

That was a question asked in my very first post to this thread. Now I think we are getting very close to the answer. The next burning question will undoubtedly be: why am I now reaching that minimum airflow OR am I and I don't know that?

Wish I had bought an anemometer long ago - especially before I did the DC Upgrade.
"Making Sawdust Safely"
Dusty
Sent from my Dell XPS using Firefox.
RFGuy
Platinum Member
Posts: 2740
Joined: Mon Dec 31, 2018 8:05 am
Location: a suburb of PHX, AZ

Re: Rate of Air Flow vs Volume of Air Flow

Post by RFGuy »

dusty wrote: Sun Nov 27, 2022 4:44 pm What rate of airflow should I expect to see?

That was a question asked in my very first post to this thread. Now I think we are getting very close to the answer. The next burning question will undoubtedly be: why am I now reaching that minimum airflow OR am I and I don't know that?

Wish I had bought an anemometer long ago - especially before I did the DC Upgrade.
Dusty,

Do you agree with me on the area calculation? A 2-1/2" port (2.25" ID) should have an area of 0.028ft².

I referred to my previous thread on this earlier that details all of my prior anemometer measurements on my DC-3300. I will list them again here. I would expect at least this airspeed and airflow from your upgraded DC-3300. The fact that you are seeing lower airspeed than what I reported is concerning, I believe, and should be investigated.


AIRSPEED - <measured>
1 port open at a time: (units=ft/min)
Left: 4944 Center: 4494 Right: 4894

2 ports open at a time: (units=ft/min)
Left: 3411 Right: 3388

3 ports open at a time: (units=ft/min)
Left: 2584 Center: 2497 Right: 2479


AIRFLOW - <calculated>
1 port open at a time: (units=CFM)
Left: 142.7 Center: 129.7 Right: 141.2

2 ports open at a time: (units=CFM)
Left: 98.4 Right: 97.8

3 ports open at a time: (units=CFM)
Left: 74.6 Center: 72.0 Right: 71.5


FULL DESCRIPTION OF THESE MEASUREMENTS AT LINK BELOW:
viewtopic.php?p=285543#p285543
📶RF Guy

Mark V 520 (Bought New '98) | 4" jointer | 6" beltsander | 12" planer | bandsaw | router table | speed reducer | univ. tool rest
Porter Cable 12" Compound Miter Saw | Rikon 8" Low Speed Bench Grinder w/CBN wheels | Jessem Clear-Cut TS™ Stock Guides
Festool (Emerald): DF 500 Q | RO 150 FEQ | OF 1400 EQ | TS 55 REQ | CT 26 E
DC3300 | Shopvac w/ClearVue CV06 Mini Cyclone | JDS AirTech 2000 | Sundstrom PAPR | Dylos DC1100 Pro particulate monitor
Matanuska
Gold Member
Posts: 96
Joined: Sun Jan 02, 2022 8:07 pm
Location: Dallas, Texas

Re: Rate of Air Flow vs Volume of Air Flow

Post by Matanuska »

RFGuy wrote: Sun Nov 27, 2022 2:10 pm
Matanuska wrote: Sun Nov 27, 2022 1:50 pm Perhaps I misunderstood the suggestion, but sealing the flow path between the anemometer and the suction inlet could erroneously change the measured velocity if the anemometer diameter is different than the suction inlet.
Matanuska,

Dusty has measured 2990 fpm airspeed using an off the shelf anemometer and this reading was taken from a 2-1/4" round dust port from the DC-3300. So, I believe any airflow (CFM) calculation MUST be performed using the area of a circle of diameter 2.25", for this particular case with the DC-3300. Do you agree with this?
It depends on whether the anemometer is sealed to the inlet to capture 100% of the inlet suction airflow as well as the size of the anemometer ID relative to the suction inlet ID.

I agree that the 2.25" diameter should be used to calculate CFM if the anemometer is capturing 100% of the inlet flow and the anemometer ID is the same as the suction inlet ID. I also agree that a 2.25" ID gives 83 CFM.

If the anemometer is capturing 100% of the inlet flow but the anemometer ID is different than the suction inlet ID I believe the anemometer ID must be used to calculate CFM. If the anemometer ID is larger than the suction inlet diameter it will measure a lower velocity (ft/min) than the velocity that is entering the inlet suction. Of course this assumes incompressible flow which isn't really the case for gas flow, but it will probably be close. If the anemometer ID is 3" and the suction inlet ID is 2.25" I believe a 2990 fpm 100% flow at the anemometer would correspond to 147 CFM at both the anemometer and the suction inlet. 147 CFM at the 2.25" suction inlet will have a velocity of about 5250 fpm due to its smaller area. Are we on the same page?
1985 Mark V upgraded to 520 PowerPro. Shopsmith cast iron table bandsaw, jointer, belt sander, and 60's vintage 610 jigsaw SPT's. Makita 2040 15" planer, JessEm Mast-R-Lift II router table.
User avatar
dusty
Platinum Member
Posts: 21359
Joined: Wed Nov 22, 2006 6:52 am
Location: Tucson (Wildcat Country), Arizona

Re: Rate of Air Flow vs Volume of Air Flow

Post by dusty »

I am learning a lot here but NO I have not gotten there yet.
"Making Sawdust Safely"
Dusty
Sent from my Dell XPS using Firefox.
User avatar
JPG
Platinum Member
Posts: 34610
Joined: Wed Dec 10, 2008 7:42 pm
Location: Lexington, Ky (TAMECAT territory)

Re: Rate of Air Flow vs Volume of Air Flow

Post by JPG »

If the anemometer is capturing 100% of the inlet flow but the anemometer ID is different than the suction inlet ID I believe the anemometer ID must be used to calculate CFM. If the anemometer ID is larger than the suction inlet diameter it will measure a lower velocity (ft/min) than the velocity that is entering the inlet suction. Of course this assumes incompressible flow which isn't really the case for gas flow, but it will probably be close. If the anemometer ID is 3" and the suction inlet ID is 2.25" I believe a 2990 fpm 100% flow at the anemometer would correspond to 147 CFM at both the anemometer and the suction inlet. 147 CFM at the 2.25" suction inlet will have a velocity of about 5250 fpm due to its smaller area. Are we on the same page?

I think SO!!!
╔═══╗
╟JPG ╢
╚═══╝

Goldie(Bought New SN 377425)/4" jointer/6" beltsander/12" planer/stripsander/bandsaw/powerstation /Scroll saw/Jig saw /Craftsman 10" ras/Craftsman 6" thicknessplaner/ Dayton10"tablesaw(restoredfromneighborstrashpile)/ Mark VII restoration in 'progress'/ 10
E[/size](SN E3779) restoration in progress, a 510 on the back burner and a growing pile of items to be eventually returned to useful life. - aka Red Grange
RFGuy
Platinum Member
Posts: 2740
Joined: Mon Dec 31, 2018 8:05 am
Location: a suburb of PHX, AZ

Re: Rate of Air Flow vs Volume of Air Flow

Post by RFGuy »

Matanuska wrote: Sun Nov 27, 2022 5:47 pm It depends on whether the anemometer is sealed to the inlet to capture 100% of the inlet suction airflow as well as the size of the anemometer ID relative to the suction inlet ID.

I agree that the 2.25" diameter should be used to calculate CFM if the anemometer is capturing 100% of the inlet flow and the anemometer ID is the same as the suction inlet ID. I also agree that a 2.25" ID gives 83 CFM.

If the anemometer is capturing 100% of the inlet flow but the anemometer ID is different than the suction inlet ID I believe the anemometer ID must be used to calculate CFM. If the anemometer ID is larger than the suction inlet diameter it will measure a lower velocity (ft/min) than the velocity that is entering the inlet suction. Of course this assumes incompressible flow which isn't really the case for gas flow, but it will probably be close. If the anemometer ID is 3" and the suction inlet ID is 2.25" I believe a 2990 fpm 100% flow at the anemometer would correspond to 147 CFM at both the anemometer and the suction inlet. 147 CFM at the 2.25" suction inlet will have a velocity of about 5250 fpm due to its smaller area. Are we on the same page?
Matanuska,

Thanks. I appreciate it. These cheap anemometers don't measure airflow (CFM), but instead calculate it based on a user input area. Also, they are commonly sold and used in the HVAC area where commonly they are held in front of a much larger aperture such as a supply register for the HVAC system. As such, measured airspeed is independent of either the supply register size or the anemometer suction inlet size as I understand it. However, since dust collectors are often spec'ed in terms of airflow that is what we are attempting to get to and there-in lies the question...how to specify airflow and at what reference plane? Since a DC-3300 ultimately connects to a 2-1/2" hose and a 2-1/2" port on the Mark V, the airflow gets choked down through it. This is why I am trying to standardize on agreed upon terms and how to specify the airflow on this thread. Shopsmith specs the DC-3300 as a 330 CFM dust collector, but I see that as more of the design value and not a measured value. I don't believe ANYONE has ever measured 330 CFM through a single 2-1/2" port on the DC-3300. The most I can get through a single port of my DC-3300 is 142.7 CFM. Rather, I think the 330 CFM was the intended target spec for the DC-3300 and can only be achieved through the 4.5" port of the DC-3300 with the 3 port manifold removed. Calculation wise we are both on the same page and I appreciate any additional insights you might have to help this conversation. As far as I know I am the only one to ever measure the DC-3300 dust collector using an anemometer; that is until Dusty's recent purchase. IF we can all agree on where and how to measure/calculate airflow then it would be helpful because then Dusty can measure it on his upgraded DC-3300 (DC-6000 upgrade kit) and finally report to us how much, if any, improvement is obtained via upgrading to Shopsmith's new DC-6000 upgrade kit.
📶RF Guy

Mark V 520 (Bought New '98) | 4" jointer | 6" beltsander | 12" planer | bandsaw | router table | speed reducer | univ. tool rest
Porter Cable 12" Compound Miter Saw | Rikon 8" Low Speed Bench Grinder w/CBN wheels | Jessem Clear-Cut TS™ Stock Guides
Festool (Emerald): DF 500 Q | RO 150 FEQ | OF 1400 EQ | TS 55 REQ | CT 26 E
DC3300 | Shopvac w/ClearVue CV06 Mini Cyclone | JDS AirTech 2000 | Sundstrom PAPR | Dylos DC1100 Pro particulate monitor
Matanuska
Gold Member
Posts: 96
Joined: Sun Jan 02, 2022 8:07 pm
Location: Dallas, Texas

Re: Rate of Air Flow vs Volume of Air Flow

Post by Matanuska »

I did some on-line sleuthing and learned a few things about dust collection blower specs. Blower CFM ratings are associated with a specific static pressure (suction pressure, or the pressure drop caused by frictional losses through the flow system being overcome by the fan at a given CFM). The max CFM occurs for zero pressure drop (no flow lines or fittings attached to the blower). The maximum suction pressure generated by a blower occurs at zero CFM and can be measured by connecting the blower suction inlet to a manometer. CFM decreases as static pressure losses increase. Duct length, fittings, and duct smoothness all contribute to static pressure loss. Blower manufacturers can provide plots of CFM vs. static pressure drop for a given blower.

If a blower's CFM rating is specified without an associated static pressure, the rating is probably the max CFM at zero pressure drop (no duct or fittings) so that would explain why dust collection systems with fittings and hose have lower CFM's. Knowing this, I'd suggest the easiest way to compare blower CFM's would be to use the zero pressure drop max CFM value. I found a YouTube video showing how to measure both max CFM and max static pressure for a blower. Search YouTube for "Measuring Airflow for a Dust Collector | Static Suction & Air Velocity".
1985 Mark V upgraded to 520 PowerPro. Shopsmith cast iron table bandsaw, jointer, belt sander, and 60's vintage 610 jigsaw SPT's. Makita 2040 15" planer, JessEm Mast-R-Lift II router table.
RFGuy
Platinum Member
Posts: 2740
Joined: Mon Dec 31, 2018 8:05 am
Location: a suburb of PHX, AZ

Re: Rate of Air Flow vs Volume of Air Flow

Post by RFGuy »

Matanuska wrote: Sun Nov 27, 2022 10:59 pm I did some on-line sleuthing and learned a few things about dust collection blower specs. Blower CFM ratings are associated with a specific static pressure (suction pressure, or the pressure drop caused by frictional losses through the flow system being overcome by the fan at a given CFM). The max CFM occurs for zero pressure drop (no flow lines or fittings attached to the blower). The maximum suction pressure generated by a blower occurs at zero CFM and can be measured by connecting the blower suction inlet to a manometer. CFM decreases as static pressure losses increase. Duct length, fittings, and duct smoothness all contribute to static pressure loss. Blower manufacturers can provide plots of CFM vs. static pressure drop for a given blower.

If a blower's CFM rating is specified without an associated static pressure, the rating is probably the max CFM at zero pressure drop (no duct or fittings) so that would explain why dust collection systems with fittings and hose have lower CFM's. Knowing this, I'd suggest the easiest way to compare blower CFM's would be to use the zero pressure drop max CFM value. I found a YouTube video showing how to measure both max CFM and max static pressure for a blower. Search YouTube for "Measuring Airflow for a Dust Collector | Static Suction & Air Velocity".
Matanuska,

I am not sure that this helps us converge on this thread, except for the fact that this is exactly what I did already. I measured my original DC-3300 dust collector at the 2-1/4" inlet port on the 3 port manifold. No hoses were involved so no added static pressure losses to the system. So, it makes sense, to me, that we naturally calculate airflow using that 2-1/4" inlet aperture size. Now, there is discussion on this thread of using 3" or other aperture sizes to calculate airflow for the DC-3300. I just wanted to have an apples-to-apples comparison.
📶RF Guy

Mark V 520 (Bought New '98) | 4" jointer | 6" beltsander | 12" planer | bandsaw | router table | speed reducer | univ. tool rest
Porter Cable 12" Compound Miter Saw | Rikon 8" Low Speed Bench Grinder w/CBN wheels | Jessem Clear-Cut TS™ Stock Guides
Festool (Emerald): DF 500 Q | RO 150 FEQ | OF 1400 EQ | TS 55 REQ | CT 26 E
DC3300 | Shopvac w/ClearVue CV06 Mini Cyclone | JDS AirTech 2000 | Sundstrom PAPR | Dylos DC1100 Pro particulate monitor
DLB
Platinum Member
Posts: 1985
Joined: Fri Nov 08, 2019 11:24 am
Location: Joshua Texas

Re: Rate of Air Flow vs Volume of Air Flow

Post by DLB »

RFGuy wrote: Mon Nov 28, 2022 6:56 am ...Now, there is discussion on this thread of using 3" or other aperture sizes to calculate airflow for the DC-3300...
What Matanuska is suggesting is that the larger aperture blade anemometer won't directly measure velocity in the manifold to support a CFM calculation in the way that a smaller anemometer would. Because, I think, blade anemometers measures average velocity over their own aperture. Therefore, use the measured velocity in this case to determine CFM through the anemometer's aperture on the presumption that the same CFM is entering the manifold.

An alternative would be to measure sans manifold, where presumably the duct size exceeds both anemometer apertures. This would give an interesting direct comparison of DC-3300 to DC-6000.

Also note that RFGuy and Dusty are using different filter hoods at the time they ran their tests, neither 'standard'. It is another unquantified variable. SS asserts higher CFM for larger hood: "Advantage of the 24" filter hood on DC3300 is that it increases airflow 30% or from 330 to 430 CFMs. 42" hood CFM range 695-890 hose is 2 1/2". Diameter plastic end makes it 2 1/4"." https://www.shopsmith.com/mediawiki/ind ... Filtration

- David
RFGuy
Platinum Member
Posts: 2740
Joined: Mon Dec 31, 2018 8:05 am
Location: a suburb of PHX, AZ

Re: Rate of Air Flow vs Volume of Air Flow

Post by RFGuy »

DLB wrote: Mon Nov 28, 2022 8:27 am
RFGuy wrote: Mon Nov 28, 2022 6:56 am ...Now, there is discussion on this thread of using 3" or other aperture sizes to calculate airflow for the DC-3300...
What Matanuska is suggesting is that the larger aperture blade anemometer won't directly measure velocity in the manifold to support a CFM calculation in the way that a smaller anemometer would. Because, I think, blade anemometers measures average velocity over their own aperture. Therefore, use the measured velocity in this case to determine CFM through the anemometer's aperture on the presumption that the same CFM is entering the manifold.

An alternative would be to measure sans manifold, where presumably the duct size exceeds both anemometer apertures. This would give an interesting direct comparison of DC-3300 to DC-6000.

Also note that RFGuy and Dusty are using different filter hoods at the time they ran their tests, neither 'standard'. It is another unquantified variable. SS asserts higher CFM for larger hood: "Advantage of the 24" filter hood on DC3300 is that it increases airflow 30% or from 330 to 430 CFMs. 42" hood CFM range 695-890 hose is 2 1/2". Diameter plastic end makes it 2 1/4"." https://www.shopsmith.com/mediawiki/ind ... Filtration

- David
David,

Yeah, I wish you hadn't referenced that inaccurate Shopsmith Wiki link above. Shopsmith used to make the filter hood information readily available on their website, but recently I noticed they took it down or moved it. Below is a past Shopsmith catalog that details the filter rating differences between the 12", 24" and 42" filter hoods. The Wiki you reference has this wrong and claims 1.5 to 2µm filtering with the "regular hood". Shopsmith has listed the 12" filter hood as filtering down to ONLY 7µm for several years. The 24" filter hood goes down to 5µm and the 42" filter hood is rated down to 1µm. I know because I have looked it up umpteen times in the past. Given the inaccuracies relating to the filter hoods in your Shopsmith Wiki link, I don't know that I can trust ANY of the other info on that Wiki page.

Accurate Catalog Description:
https://www.shopsmith.com/ownersite/Mas ... 8-08r2.pdf
ShopsmithFilterHood.jpg
ShopsmithFilterHood.jpg (192.45 KiB) Viewed 1407 times

Inaccurate Wiki Description:
ShopsmithWiki.jpg
ShopsmithWiki.jpg (91.42 KiB) Viewed 1397 times
Last edited by RFGuy on Mon Nov 28, 2022 10:40 am, edited 4 times in total.
📶RF Guy

Mark V 520 (Bought New '98) | 4" jointer | 6" beltsander | 12" planer | bandsaw | router table | speed reducer | univ. tool rest
Porter Cable 12" Compound Miter Saw | Rikon 8" Low Speed Bench Grinder w/CBN wheels | Jessem Clear-Cut TS™ Stock Guides
Festool (Emerald): DF 500 Q | RO 150 FEQ | OF 1400 EQ | TS 55 REQ | CT 26 E
DC3300 | Shopvac w/ClearVue CV06 Mini Cyclone | JDS AirTech 2000 | Sundstrom PAPR | Dylos DC1100 Pro particulate monitor
Post Reply