Rate of Air Flow vs Volume of Air Flow

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RFGuy
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Re: Rate of Air Flow vs Volume of Air Flow

Post by RFGuy »

dusty wrote: Sun Nov 27, 2022 9:27 am Proven to be true!!!

I just took a new set of readings while being much more careful about alignment between the meter and DC port. The ft/mun numbers look more realistic (2350 ft/min which I believe to be about 200 cfm).

Not very scientific but it does make me feel a bit more confident in both the DC and the anemometer. Yes, I know - my quick and easy approach would not pass muster in an engineering review.
Dusty,

What size port were you measuring? IF it was a 2-1/2" hose (2.25" ID), then the area is 0.028 ft². Using CFM = (fpm * area), a 2350 fpm airspeed is only 65.8 CFM airflow through a 2-1/2" dust port. For comparison, I get around 5,000 fpm on my DC-3300 when measuring one 2-1/2" port. Based on this, the highest I calculated was 142.7 CFM on my DC-3300 out of one port. viewtopic.php?p=285543#p285543
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algale
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Re: Rate of Air Flow vs Volume of Air Flow

Post by algale »

The hose is going to cause some issues in measurement because it it not smooth.

I'd be curious what the cfm measurement is at the DC3300/6000 at the dust port itself. Just remove the hose and take a measurement at one port (with the other ports closed off).
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RFGuy
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Re: Rate of Air Flow vs Volume of Air Flow

Post by RFGuy »

algale wrote: Sun Nov 27, 2022 10:28 am The hose is going to cause some issues in measurement because it it not smooth.

I'd be curious what the cfm measurement is at the DC3300/6000 at the dust port itself. Just remove the hose and take a measurement at one port (with the other ports closed off).
Alan,

Yeah, this is what I did in my measurements here: viewtopic.php?p=285543#p285543 It is how I got the 142.7 CFM 1 port measurement on an original (non-upgraded) DC-3300. It would be helpful if Dusty can repeat this since he has an upgraded DC-3300. The challenge for him, I think could be that the size of the fan on his anemometer looks much bigger than a 2-1/2" port and could complicate his ability to get all of the suction to go through that fan (without leaks). The model of anemometer that I purchased has a fan housing that is almost identical in size to the 2-1/2" port, so it isn't hard at all to get a good seal around my anemometer and a 2-1/2" port. I could be wrong though about the size of his anemometer though...it just looks big in the picture. The diameter of the fan in my anemometer is 2.5" diameter.
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dusty
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Re: Rate of Air Flow vs Volume of Air Flow

Post by dusty »

algale wrote: Sun Nov 27, 2022 10:28 am The hose is going to cause some issues in measurement because it it not smooth.

I'd be curious what the cfm measurement is at the DC3300/6000 at the dust port itself. Just remove the hose and take a measurement at one port (with the other ports closed off).
I can and will do that. I just regret not being able to provide "before" numbers.
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dusty
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Re: Rate of Air Flow vs Volume of Air Flow

Post by dusty »

RFGuy wrote: Sun Nov 27, 2022 10:47 am
algale wrote: Sun Nov 27, 2022 10:28 am The hose is going to cause some issues in measurement because it it not smooth.

I'd be curious what the cfm measurement is at the DC3300/6000 at the dust port itself. Just remove the hose and take a measurement at one port (with the other ports closed off).
Alan,

Yeah, this is what I did in my measurements here: viewtopic.php?p=285543#p285543 It is how I got the 142.7 CFM 1 port measurement on an original (non-upgraded) DC-3300. It would be helpful if Dusty can repeat this since he has an upgraded DC-3300. The challenge for him, I think could be that the size of the fan on his anemometer looks much bigger than a 2-1/2" port and could complicate his ability to get all of the suction to go through that fan (without leaks). The model of anemometer that I purchased has a fan housing that is almost identical in size to the 2-1/2" port, so it isn't hard at all to get a good seal around my anemometer and a 2-1/2" port. I could be wrong though about the size of his anemometer though...it just looks big in the picture. The diameter of the fan in my anemometer is 2.5" diameter.
I may have resolved the sealing issue with a piece of self adhesive foam wrapped around the face of the meter.
Port Fit.jpg
Port Fit.jpg (40.68 KiB) Viewed 616 times
Sized to fit.jpg
Sized to fit.jpg (58.5 KiB) Viewed 616 times
Quick preliminary test produced 2658 ft/min measured ---(293.57 cfm) calculated. Oh for DC3300 numbers.
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dusty
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Re: Rate of Air Flow vs Volume of Air Flow

Post by dusty »

I took a measurement on a single port (others closed) with no hose and got 2990 ft/min (330.24 cfm calculated).

I then took another measurement on the same port via a hose and got 2687 ft.min (296.77 cfm calculated).

Both are surprisingly good and warrant verification. I did do a few quick readings with multiple ports open (with and without hose and saw differences that I would expect. Need yet to collect and record that comparison data in a reliable manner. I will do that but not until I am comfortable with the previous results. No value in collecting unreliable data.
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RFGuy
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Re: Rate of Air Flow vs Volume of Air Flow

Post by RFGuy »

dusty wrote: Sun Nov 27, 2022 11:53 am I took a measurement on a single port (others closed) with no hose and got 2990 ft/min (330.24 cfm calculated).

I then took another measurement on the same port via a hose and got 2687 ft.min (296.77 cfm calculated).

Both are surprisingly good and warrant verification. I did do a few quick readings with multiple ports open (with and without hose and saw differences that I would expect. Need yet to collect and record that comparison data in a reliable manner. I will do that but not until I am comfortable with the previous results. No value in collecting unreliable data.
Dusty,

I do NOT agree with your calculations. What is the ID of the pipe you are using to connect the anemometer to the DC-3300? It looks like at least a 3" ID pipe. This will inflate the calculation and would only be true if you kept that 3" ID all the way to the tool. Shopsmith uses 2-1/2" dust ports which have an ID of 2-1/4". The only relevant CFM calculation is relative to the final limiting dimension of 2-1/2" dust ports if you intend to connect the DC-3300 up to a Shopsmith tool using a 2-1/2" dust hose.

In reverse engineering your calculations, I see that you are using a 4.5" diameter aperture to calculate CFM. Where exactly do you get this 4.5" diameter from? In order for 2990 fpm to yield 330.24 CFM it has to be a 4.5" diameter aperture, if round. Same is true for the 2687 fpm to yield 296.77 CFM. Can you explain why you chose an area equivalent to a 4.5" ID pipe for your CFM calculations?
📶RF Guy

Mark V 520 (Bought New '98) | 4" jointer | 6" beltsander | 12" planer | bandsaw | router table | speed reducer | univ. tool rest
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dusty
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Re: Rate of Air Flow vs Volume of Air Flow

Post by dusty »

RFGuy wrote: Sun Nov 27, 2022 12:12 pm
dusty wrote: Sun Nov 27, 2022 11:53 am I took a measurement on a single port (others closed) with no hose and got 2990 ft/min (330.24 cfm calculated).

I then took another measurement on the same port via a hose and got 2687 ft.min (296.77 cfm calculated).

Both are surprisingly good and warrant verification. I did do a few quick readings with multiple ports open (with and without hose and saw differences that I would expect. Need yet to collect and record that comparison data in a reliable manner. I will do that but not until I am comfortable with the previous results. No value in collecting unreliable data.
Dusty,

I do NOT agree with your calculations. What is the ID of the pipe you are using to connect the anemometer to the DC-3300? It looks like at least a 3" ID pipe. This will inflate the calculation and would only be true if you kept that 3" ID all the way to the tool. Shopsmith uses 2-1/2" dust ports which have an ID of 2-1/4". The only relevant CFM calculation is relative to the final limiting dimension of 2-1/2" dust ports if you intend to connect the DC-3300 up to a Shopsmith tool using a 2-1/2" dust hose.

In reverse engineering your calculations, I see that you are using a 4.5" diameter aperture to calculate CFM. Where exactly do you get this 4.5" diameter from? In order for 2990 fpm to yield 330.24 CFM it has to be a 4.5" diameter aperture, if round. Same is true for the 2687 fpm to yield 296.77 CFM. Can you explain why you chose an area equivalent to a 4.5" ID pipe for your CFM calculations?
That suspect pipe is a coupling from an old DC3300 2 1/2" coupling. Now the 4.5" number may be suspect. I assume you come to this conclusion as a result of my using 2.25" measurement in my calculations. That number is intended to be the diameter of the coupling between the meter and the DC.
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dusty
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Re: Rate of Air Flow vs Volume of Air Flow

Post by dusty »

dusty wrote: Sun Nov 27, 2022 12:50 pm
RFGuy wrote: Sun Nov 27, 2022 12:12 pm
dusty wrote: Sun Nov 27, 2022 11:53 am I took a measurement on a single port (others closed) with no hose and got 2990 ft/min (330.24 cfm calculated).

I then took another measurement on the same port via a hose and got 2687 ft.min (296.77 cfm calculated).

Both are surprisingly good and warrant verification. I did do a few quick readings with multiple ports open (with and without hose and saw differences that I would expect. Need yet to collect and record that comparison data in a reliable manner. I will do that but not until I am comfortable with the previous results. No value in collecting unreliable data.
Dusty,

I do NOT agree with your calculations. What is the ID of the pipe you are using to connect the anemometer to the DC-3300? It looks like at least a 3" ID pipe. This will inflate the calculation and would only be true if you kept that 3" ID all the way to the tool. Shopsmith uses 2-1/2" dust ports which have an ID of 2-1/4". The only relevant CFM calculation is relative to the final limiting dimension of 2-1/2" dust ports if you intend to connect the DC-3300 up to a Shopsmith tool using a 2-1/2" dust hose.

In reverse engineering your calculations, I see that you are using a 4.5" diameter aperture to calculate CFM. Where exactly do you get this 4.5" diameter from? In order for 2990 fpm to yield 330.24 CFM it has to be a 4.5" diameter aperture, if round. Same is true for the 2687 fpm to yield 296.77 CFM. Can you explain why you chose an area equivalent to a 4.5" ID pipe for your CFM calculations?

Changing that would certainly deflate those numbers.
That suspect pipe is a coupling from an old DC3300 2 1/2" coupling. Now the 4.5" number may be suspect. I assume you come to this conclusion as a result of my using 2.25" measurement in my calculations. That number is intended to be the diameter of the coupling between the meter and the DC.
"Making Sawdust Safely"
Dusty
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RFGuy
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Re: Rate of Air Flow vs Volume of Air Flow

Post by RFGuy »

dusty wrote: Sun Nov 27, 2022 12:50 pm That suspect pipe is a coupling from an old DC3300 2 1/2" coupling. Now the 4.5" number may be suspect. I assume you come to this conclusion as a result of my using 2.25" measurement in my calculations. That number is intended to be the diameter of the coupling between the meter and the DC.
Dusty,

CFM = (fpm * area)

You measured 2990 fpm.

Assuming a 2-1/2" port (2-1/4" ID),

A=πr² and d = 2 * r (for a circle)

So, area = 3.14159 * (2.25/2/12)² = 0.027611631 = 0.028 ft² (rounding up)

Therefore,

CFM = 2990 fpm * 0.028 ft² = 83.72 CFM for 2-1/2" hose aperture.

NOTE: In area calculation above, 2.25" is divided by 2 to go from diameter to radius. Then it is divided by 12 to convert from inches to feet so that units align with fpm in CFM calculation.

P.S. I still think something isn't quite right with your airspeed (fpm) measurement. I get almost 5,000 fpm out of a 2-1/2" port on my DC-3300, so I am surprised that you are measuring about half that with your anemometer. Airspeed is measured and not calculated, so I don't understand why you are only getting 2990 fpm.
📶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
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