Rate of Air Flow vs Volume of Air Flow

[dusty]

...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

Bad graphic presentation on my part. The anemometer image that I posted appears to be 3" but it is really much closer to 2 1/2".

[RFGuy]

Bad graphic presentation on my part. The anemometer image that I posted appears to be 3" but it is really much closer to 2 1/2".

Dusty,

Thanks. This helps, I think. I went back and looked at your picture and it does look like the ruler shows the fan on your anemometer is about 2.5" in diameter. My anemometer has a 2.5" fan, so I think we can assume our anemometers are similar and hopefully should give similar readings. I am still baffled though because you are only getting about half the airspeed that I measure with my original DC-3300. The only difference besides the DC-6000 upgrade kit, I believe, is that I have the 42" filter hood on my DC-3300. I really think you should be getting much more airspeed than what you are seeing so far...unless that 12" filter hood is really that restrictive.

[dusty]

Bad graphic presentation on my part. The anemometer image that I posted appears to be 3" but it is really much closer to 2 1/2".

Dusty,

Thanks. This helps, I think. I went back and looked at your picture and it does look like the ruler shows the fan on your anemometer is about 2.5" in diameter. My anemometer has a 2.5" fan, so I think we can assume our anemometers are similar and hopefully should give similar readings. I am still baffled though because you are only getting about half the airspeed that I measure with my original DC-3300. The only difference besides the DC-6000 upgrade kit, I believe, is that I have the 42" filter hood on my DC-3300. I really think you should be getting much more airspeed than what you are seeing so far...unless that 12" filter hood is really that restrictive.

I just measured the aperture on the anemometer at 2.58". I am attempting to devise some sort of "coupler" between the meter and the DC in an effort to get more repeatable readings.

[dusty]

OKAY - I must confess. I have created a lot of confusion in this thread caused in part my my ignorance and by my not being consistent with my actions during testing. My numbers have been with and without hoses and couplings. They have been with kluged couplers between the anemometer and the DC.

Until I can establish some repeatability here in my own shop I am going to resist posting any numbers. Furthermore, until I have repeatability I am going to make all air flow measurements without the hose and with as few couplings as possible. Including the hose in my setup really hoses my numbers.

Thanks for the help provided thus far.

[jsburger]

DLB said in an earlier post...

"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. "

I mentioned in another thread that DC manufacturers specify CFM without filters in place. That is the only way (IMO) to get meaningful numbers for comparison. Filter size, type, material, new, old, clean, dirty, how dirty etc. all effect the air flow through the system just as hoses and connectors do.

Without a level playing field no two sets of numbers will be the same from two different test machines

[RFGuy]

DLB said in an earlier post...

"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. "

I mentioned in another thread that DC manufacturers specify CFM without filters in place. That is the only way (IMO) to get meaningful numbers for comparison. Filter size, type, material, new, old, clean, dirty, how dirty etc. all effect the air flow through the system just as hoses and connectors do.

Without a level playing field no two sets of numbers will be the same from two different test machines

John,

I don't find this helpful. As a methodology, I have always sought to test products in the real world application as much as possible. This guided me well in design engineering throughout my career. While there may be 1 or 2 dust collector manufacturers that do shady things like test their dust collector unloaded, without even a filter installed, I find this practice to be unscrupulous. Yes, there will be differences dependent on what filter is installed, but that is what I hope we can get to the bottom of with some actual measured data from hopefully more than one forum member. Also, why I am trying to get measurements to be taken as close to the 3 port manifold as possible for comparison. All that I am interested in is getting reasonable data to compare like-to-like. I am not expecting Dusty, myself or anyone else to get absolute numbers here and wouldn't be surprised if there is at least a 10% measurement error due to different test equipment, differences in test setup, different DC-3300 performance, etc., etc. Just trying to get a reasonable assessment and then use that to compare perhaps original DC-3300 to upgraded DC-3300 to DC-6000. In short, I am just looking for data to get "in the ballpark" for discussion here. However, right now, Dusty's anemometer is 2x from my measurement which I think needs more investigation. It very well may be that all of the difference is the 12" filter hood vs. the 42" filter hood, but let's see where the data takes us first. Lastly, measuring without a filter in place actually tells us nothing about anticipated dust collection performance in-the-application which is what we want to know.

[jsburger]

DLB said in an earlier post...

"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. "

I mentioned in another thread that DC manufacturers specify CFM without filters in place. That is the only way (IMO) to get meaningful numbers for comparison. Filter size, type, material, new, old, clean, dirty, how dirty etc. all effect the air flow through the system just as hoses and connectors do.

Without a level playing field no two sets of numbers will be the same from two different test machines

John,

I don't find this helpful. As a methodology, I have always sought to test products in the real world application as much as possible. This guided me well in design engineering throughout my career. While there may be 1 or 2 dust collector manufacturers that do shady things like test their dust collector unloaded, without even a filter installed, I find this practice to be unscrupulous. Yes, there will be differences dependent on what filter is installed, but that is what I hope we can get to the bottom of with some actual measured data from hopefully more than one forum member. Also, why I am trying to get measurements to be taken as close to the 3 port manifold as possible for comparison. All that I am interested in is getting reasonable data to compare like-to-like. I am not expecting Dusty, myself or anyone else to get absolute numbers here and wouldn't be surprised if there is at least a 10% measurement error due to different test equipment, differences in test setup, different DC-3300 performance, etc., etc. Just trying to get a reasonable assessment and then use that to compare perhaps original DC-3300 to upgraded DC-3300 to DC-6000. In short, I am just looking for data to get "in the ballpark" for discussion here. However, right now, Dusty's anemometer is 2x from my measurement which I think needs more investigation. It very well may be that all of the difference is the 12" filter hood vs. the 42" filter hood, but let's see where the data takes us first. Lastly, measuring without a filter in place actually tells us nothing about anticipated dust collection performance in-the-application which is what we want to know.

OK, I will keep my mouth shut.

[dusty]

DLB said in an earlier post...

"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. "

I mentioned in another thread that DC manufacturers specify CFM without filters in place. That is the only way (IMO) to get meaningful numbers for comparison. Filter size, type, material, new, old, clean, dirty, how dirty etc. all effect the air flow through the system just as hoses and connectors do.

Without a level playing field no two sets of numbers will be the same from two different test machines

John,

I don't find this helpful. As a methodology, I have always sought to test products in the real world application as much as possible. This guided me well in design engineering throughout my career. While there may be 1 or 2 dust collector manufacturers that do shady things like test their dust collector unloaded, without even a filter installed, I find this practice to be unscrupulous. Yes, there will be differences dependent on what filter is installed, but that is what I hope we can get to the bottom of with some actual measured data from hopefully more than one forum member. Also, why I am trying to get measurements to be taken as close to the 3 port manifold as possible for comparison. All that I am interested in is getting reasonable data to compare like-to-like. I am not expecting Dusty, myself or anyone else to get absolute numbers here and wouldn't be surprised if there is at least a 10% measurement error due to different test equipment, differences in test setup, different DC-3300 performance, etc., etc. Just trying to get a reasonable assessment and then use that to compare perhaps original DC-3300 to upgraded DC-3300 to DC-6000. In short, I am just looking for data to get "in the ballpark" for discussion here. However, right now, Dusty's anemometer is 2x from my measurement which I think needs more investigation. It very well may be that all of the difference is the 12" filter hood vs. the 42" filter hood, but let's see where the data takes us first. Lastly, measuring without a filter in place actually tells us nothing about anticipated dust collection performance in-the-application which is what we want to know.

I want to see consistent numbers as much as anyone and I am working to achieve that on my machine. My current plan is to develop a means to attach the anemometer so that it is mounted "the same" each and every time. I plan not to test with hoses until I have achieved that. I will be testing and recording but I will not post numbers until I truly believe they are realistic. I would like to do this without dedicating my anemometer to the Shopsnmith DC System but I am prepared to do that if I can not fing another way. Wish me luck.

[dusty]

I am seeking confirmation.

Am I correct with the assumption that to achieve 200cfm through a 2 1/4" hose will require at least 7250 ft/min airflow?

If so, the outlook is bleak.

[RFGuy]

I am seeking confirmation.

Am I correct with the assumption that to achieve 200cfm through a 2 1/4" hose will require at least 7250 ft/min airflow?

If so, the outlook is bleak.

Dusty,

Yes, this is correct. Also, why I have not understood the guidance from Jim on what the DC-3300, upgraded DC-3300, or DC-6000 are capable of. That 3 port manifold is VERY restrictive and then the limitation of a 2-1/4" port is also very limiting. I can get almost 5000 ft/min out of 1 port on mine, but that is it. Again, I am not trying to knock the new DC-3300 upgrade kit or even the DC-6000, but I just want honesty of what to expect from them. I do think the upgrades probably give some improvement, but we need to quantify what that improvement is and whether you can even see it with the 3 port manifold installed.