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Re: Rate of Air Flow vs Volume of Air Flow
Posted: Sun Nov 27, 2022 9:37 am
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
Re: Rate of Air Flow vs Volume of Air Flow
Posted: Sun Nov 27, 2022 10:28 am
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).
Re: Rate of Air Flow vs Volume of Air Flow
Posted: Sun Nov 27, 2022 10:47 am
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.
Re: Rate of Air Flow vs Volume of Air Flow
Posted: Sun Nov 27, 2022 10:55 am
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.
Re: Rate of Air Flow vs Volume of Air Flow
Posted: Sun Nov 27, 2022 11:06 am
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 (40.68 KiB) Viewed 706 times
- Sized to fit.jpg (58.5 KiB) Viewed 706 times
Quick preliminary test produced 2658 ft/min measured ---(293.57 cfm) calculated. Oh for DC3300 numbers.
Re: Rate of Air Flow vs Volume of Air Flow
Posted: Sun Nov 27, 2022 11:53 am
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.
Re: Rate of Air Flow vs Volume of Air Flow
Posted: Sun Nov 27, 2022 12:12 pm
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?
Re: Rate of Air Flow vs Volume of Air Flow
Posted: Sun Nov 27, 2022 12:50 pm
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.
Re: Rate of Air Flow vs Volume of Air Flow
Posted: Sun Nov 27, 2022 12:52 pm
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.
Re: Rate of Air Flow vs Volume of Air Flow
Posted: Sun Nov 27, 2022 12:57 pm
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.