Is there poor mans CFM meter or a simple JIG one can rig up to estimate the
CFM being pulled by a dust collector through a 4 " pipe?
Maybe some sort of calculation based on the deflection of a known
size/weight object at the measured opening diameter of the intake? Object
might pendulum from top edge of opening.
thanks
On Apr 26, 11:27 am, "trs80" <[email protected]> wrote:
> Is there poor mans CFM meter or a simple JIG one can rig up to estimate the
> CFM being pulled by a dust collector through a 4 " pipe?
>
> Maybe some sort of calculation based on the deflection of a known
> size/weight object at the measured opening diameter of the intake? Object
> might pendulum from top edge of opening.
>
> thanks
I remember a year or so ago when someone posted here that he'd found a
fairly inexpensive wind meter, which he used at the end of the duct to
measure the air speed, then used that to calculate CFM moving through
the four inch tube.
I don't have time to search for it till later tonight but I remember
googling on it then and found that you can get a pretty reasonable
figure for your cfm using wind speed and size of duct. The sides of
the duct will affect it - smooth sides as in solid sections are better
than rough as in flexible tubing, but you can still get a good idea.
On Apr 26, 9:27 am, "trs80" <[email protected]> wrote:
> Is there poor mans CFM meter or a simple JIG one can rig up to estimate the
> CFM being pulled by a dust collector through a 4 " pipe?
A plastic garbage bag. Time how long it takes to fill up.
Wind velocity is one thing you can sense, but until
you understand the way that velocity is mapped to the
full surface area of the pipe, it isn't enough.
Back pressure is another thing you can sense, and if
your pipe is long enough (to get away from turbulence
at the ends) a U-tube manometer with some water in it
can be attached to the pipe at two points in the flow,
and the resulting pressure measurement (like, "in two feet of 4"
pipe, there was 25mm of water pressure drop") will be roughly
proportional to the square of the flow rate.
You can use such a U-tube and calibrate with the plastic bag
and get some idea when your filters are clogged (and stopping the
flow). You can also use a U-tube (or any other) manometer
for sensing the backpressure from the filter inlet and outlet
and this also tells you when the filters are clogged, but isn't
sensitive to inlet port choking. In filter rooms I'm familiar with,
this measurement (the backpressure across the filter) is
the important indicator of performance.
trs80 wrote:
| Is there poor mans CFM meter or a simple JIG one can rig up to
| estimate the CFM being pulled by a dust collector through a 4 "
| pipe?
Try a Google group search on alt.solar.thermal for "Air Flow
measurements".
Inexpensive _and_ accurate.
--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/
trs80 wrote:
>
> Is there poor mans CFM meter or a simple JIG one can rig up to estimate the
> CFM being pulled by a dust collector through a 4 " pipe?
>
> Maybe some sort of calculation based on the deflection of a known
> size/weight object at the measured opening diameter of the intake? Object
> might pendulum from top edge of opening.
>
> thanks
Bottom line answer - depending on your definition of "poor" -
is probably NO. If about a hundred bucks and some of your
time learning about how to use an instrument, how, where
and when to take measurements and record them, and what
calculations are needed for converting your data to the
an answer (ie Feet Per Minute air flow at your measuring
instrument, and calculated Cubic Feet Per Minute) is
acceptable
THEN
You're in luck.
I just got off the phone with Bill. Hopefully what follows
will save him a few more e-mails. Here's the minimum
you're going to need to get ACTUAL FPM and CFM in terms
of measuring equiptment
Dwyer Model 4010 Magnahelic (about $50-60 US used of eBay
or three times that for new from Magnahelich
http://www.nciweb.net/capsuhel.htm
look for Model 4010
Dwyer 166 pitot tube 6" long (can get to the center of a 12"
diameter duct) -eBay running in the $50-60 range, triple
that if buying new.
http://www.nciweb.net/dwyer_air-velocity_series-160.htm
Combined, these two give you Feet Per Minute - at the
point where the end of the pitot tube is located.. If
that's at the center of the duct you're getting the Max
speed in the round duct. Because the air is moving
slower the closer you get to the walls of the duct
(friction starts slowing the air flow down), a rough
estimate of average speed is Max Speed x 0.90.
With the Average Feet Per Minute speed and the cross
sectional area of the inside of the duct you can
calculate the Cubic Feet Per Minute (CFM) by multiplying
the Average FPM x the Cross Sectional Area of the inside
of the duct (in Square Feet, not square inches).
Note: getting the pitot tube aligned right and postioned
in the center of the duct is up to you. The instruments
will measure a pressure differential. You have to
make sure you put it where you want it to be.
Now as to hand held plastic"wind meters" - the little
things with the plastic fan blade. They're intended
to measure wind speeds you can stand in - not hurricane
speeds. In a dust collector you're looking for 3700
to 3800 feet per minute, AT A MINIMUM, air speed.
http://BillPentz.com/woodworking/cyclone/DC4Dummies.cfm#Airspeed
That's around 42 to 43 MPH. On larger dust collectors you
might get air speeds well above that depending on where you're
measuring. Above 70 mph the plastic hand held may
fail / come apart. Then there's the affect of the
body of the unit and your hand holding it - in a relatively
small opening - vs over your head while standing on
the beach or mountain top - in the middle of a hurricane
(on the leading edge or trailing edge, not in the "eye")
Turbulence in the air stream being measure raises all
kinds of hell in air flow.
For more on the basics read, and understand the FAQ
on Bill's site.
http://BillPentz.com/woodworking/cyclone/FAQs.cfm
And PLEASE - don't e-mail him for a while - he's got
his hands really full right now.
Hope this helps.
charlie b
"trs80" <[email protected]> wrote:
>whats that have to do with airflow...lexy" <[email protected]> wrote in
>message news:[email protected]...
>> "trs80" <[email protected]> wrote:
>>
>>>thanks. what is an ammeter?
>>
>> Given your moniker, I'll point you to this one:
>>
>> http://www.radioshack.com/product/index.jsp?parentPage=search&summary=summary&cp=&productId=2103173&accessories=accessories&kw=ammeter&techSpecs=techSpecs¤tTab=summary&custRatings=custRatings&sr=1&features=features&origkw=ammeter&support=support&tab=features
>>
>>
>> --
>> Alex -- Replace "nospam" with "mail" to reply by email. Checked
>> infrequently.
I was thinking that the current you drew would be in proportional to
the amount of air you move. But others that sound more knowledgable
than I said that wouldn't help. And as I think a little about it, it
seems that the current you draw (power you use) would depend both on
the CFM and the pressure (suction). Sorry for the bum steer.
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.
thanks. what is an ammeter?
"alexy" <[email protected]> wrote in message
news:[email protected]...
> "trs80" <[email protected]> wrote:
>
>>Is there poor mans CFM meter or a simple JIG one can rig up to estimate
>>the
>>CFM being pulled by a dust collector through a 4 " pipe?
>>
>>Maybe some sort of calculation based on the deflection of a known
>>size/weight object at the measured opening diameter of the intake? Object
>>might pendulum from top edge of opening.
>>
>>thanks
>>
> Any jig you can rig up will likely tell you relative CFM, but without
> a way to calibrate it, you will only be able to tell whether you are
> drawing more CFM from this port or that. If you use only one port at a
> time, and ammeter on the line going to your DC may be just as useful
> as a jig.
> --
> Alex -- Replace "nospam" with "mail" to reply by email. Checked
> infrequently.
great input. thanks
"charlieb" <[email protected]> wrote in message
news:[email protected]...
> trs80 wrote:
>>
>> Is there poor mans CFM meter or a simple JIG one can rig up to estimate
>> the
>> CFM being pulled by a dust collector through a 4 " pipe?
>>
>> Maybe some sort of calculation based on the deflection of a known
>> size/weight object at the measured opening diameter of the intake?
>> Object
>> might pendulum from top edge of opening.
>>
>> thanks
>
> Bottom line answer - depending on your definition of "poor" -
> is probably NO. If about a hundred bucks and some of your
> time learning about how to use an instrument, how, where
> and when to take measurements and record them, and what
> calculations are needed for converting your data to the
> an answer (ie Feet Per Minute air flow at your measuring
> instrument, and calculated Cubic Feet Per Minute) is
> acceptable
>
> THEN
>
> You're in luck.
>
> I just got off the phone with Bill. Hopefully what follows
> will save him a few more e-mails. Here's the minimum
> you're going to need to get ACTUAL FPM and CFM in terms
> of measuring equiptment
>
> Dwyer Model 4010 Magnahelic (about $50-60 US used of eBay
> or three times that for new from Magnahelich
> http://www.nciweb.net/capsuhel.htm
> look for Model 4010
>
> Dwyer 166 pitot tube 6" long (can get to the center of a 12"
> diameter duct) -eBay running in the $50-60 range, triple
> that if buying new.
> http://www.nciweb.net/dwyer_air-velocity_series-160.htm
>
> Combined, these two give you Feet Per Minute - at the
> point where the end of the pitot tube is located.. If
> that's at the center of the duct you're getting the Max
> speed in the round duct. Because the air is moving
> slower the closer you get to the walls of the duct
> (friction starts slowing the air flow down), a rough
> estimate of average speed is Max Speed x 0.90.
>
> With the Average Feet Per Minute speed and the cross
> sectional area of the inside of the duct you can
> calculate the Cubic Feet Per Minute (CFM) by multiplying
> the Average FPM x the Cross Sectional Area of the inside
> of the duct (in Square Feet, not square inches).
>
> Note: getting the pitot tube aligned right and postioned
> in the center of the duct is up to you. The instruments
> will measure a pressure differential. You have to
> make sure you put it where you want it to be.
>
> Now as to hand held plastic"wind meters" - the little
> things with the plastic fan blade. They're intended
> to measure wind speeds you can stand in - not hurricane
> speeds. In a dust collector you're looking for 3700
> to 3800 feet per minute, AT A MINIMUM, air speed.
> http://BillPentz.com/woodworking/cyclone/DC4Dummies.cfm#Airspeed
>
> That's around 42 to 43 MPH. On larger dust collectors you
> might get air speeds well above that depending on where you're
> measuring. Above 70 mph the plastic hand held may
> fail / come apart. Then there's the affect of the
> body of the unit and your hand holding it - in a relatively
> small opening - vs over your head while standing on
> the beach or mountain top - in the middle of a hurricane
> (on the leading edge or trailing edge, not in the "eye")
> Turbulence in the air stream being measure raises all
> kinds of hell in air flow.
>
> For more on the basics read, and understand the FAQ
> on Bill's site.
>
> http://BillPentz.com/woodworking/cyclone/FAQs.cfm
>
> And PLEASE - don't e-mail him for a while - he's got
> his hands really full right now.
>
> Hope this helps.
>
> charlie b
If I make my own slack tube Manometer, do both ends of the manometer have to
be the same opening diameter? Could I put a npt in the outside the duct
connected to plastic slack tube with a metal tube inside and the metal tube
opening being smaller then the opening at the other end of the plastic tube?
Then measure water column difference to calculate the cfm?
thanks again
"charlieb" <[email protected]> wrote in message
news:[email protected]...
> trs80 wrote:
>>
>> Is there poor mans CFM meter or a simple JIG one can rig up to estimate
>> the
>> CFM being pulled by a dust collector through a 4 " pipe?
>>
>> Maybe some sort of calculation based on the deflection of a known
>> size/weight object at the measured opening diameter of the intake?
>> Object
>> might pendulum from top edge of opening.
>>
>> thanks
>
> Bottom line answer - depending on your definition of "poor" -
> is probably NO. If about a hundred bucks and some of your
> time learning about how to use an instrument, how, where
> and when to take measurements and record them, and what
> calculations are needed for converting your data to the
> an answer (ie Feet Per Minute air flow at your measuring
> instrument, and calculated Cubic Feet Per Minute) is
> acceptable
>
> THEN
>
> You're in luck.
>
> I just got off the phone with Bill. Hopefully what follows
> will save him a few more e-mails. Here's the minimum
> you're going to need to get ACTUAL FPM and CFM in terms
> of measuring equiptment
>
> Dwyer Model 4010 Magnahelic (about $50-60 US used of eBay
> or three times that for new from Magnahelich
> http://www.nciweb.net/capsuhel.htm
> look for Model 4010
>
> Dwyer 166 pitot tube 6" long (can get to the center of a 12"
> diameter duct) -eBay running in the $50-60 range, triple
> that if buying new.
> http://www.nciweb.net/dwyer_air-velocity_series-160.htm
>
> Combined, these two give you Feet Per Minute - at the
> point where the end of the pitot tube is located.. If
> that's at the center of the duct you're getting the Max
> speed in the round duct. Because the air is moving
> slower the closer you get to the walls of the duct
> (friction starts slowing the air flow down), a rough
> estimate of average speed is Max Speed x 0.90.
>
> With the Average Feet Per Minute speed and the cross
> sectional area of the inside of the duct you can
> calculate the Cubic Feet Per Minute (CFM) by multiplying
> the Average FPM x the Cross Sectional Area of the inside
> of the duct (in Square Feet, not square inches).
>
> Note: getting the pitot tube aligned right and postioned
> in the center of the duct is up to you. The instruments
> will measure a pressure differential. You have to
> make sure you put it where you want it to be.
>
> Now as to hand held plastic"wind meters" - the little
> things with the plastic fan blade. They're intended
> to measure wind speeds you can stand in - not hurricane
> speeds. In a dust collector you're looking for 3700
> to 3800 feet per minute, AT A MINIMUM, air speed.
> http://BillPentz.com/woodworking/cyclone/DC4Dummies.cfm#Airspeed
>
> That's around 42 to 43 MPH. On larger dust collectors you
> might get air speeds well above that depending on where you're
> measuring. Above 70 mph the plastic hand held may
> fail / come apart. Then there's the affect of the
> body of the unit and your hand holding it - in a relatively
> small opening - vs over your head while standing on
> the beach or mountain top - in the middle of a hurricane
> (on the leading edge or trailing edge, not in the "eye")
> Turbulence in the air stream being measure raises all
> kinds of hell in air flow.
>
> For more on the basics read, and understand the FAQ
> on Bill's site.
>
> http://BillPentz.com/woodworking/cyclone/FAQs.cfm
>
> And PLEASE - don't e-mail him for a while - he's got
> his hands really full right now.
>
> Hope this helps.
>
> charlie b
An ammeter is still not going to give you a flow measurement. It will only
tell you how much electrical current your system is pulling.
Air flow can be a tricky science, even to get a relatively low accuracy
measurement. Some people spend their entire carrer on just this one area of
measurement science. I wouldn't expect to find a simple and cheap way to do
it.
You probably will not find an air flow meter for less than around $250 that
will give you a readout in CFM and then it won't be a real accurate
measurement. Probably in the range of +/- 10% uncertainty.
I thin that a paddlewheel type of anemommeter would be your best bet. They
work like a fan in reverse. The air flow turns the fan blades and the speed
is measured. This gives an air velocity measurement and the Volume in CFM is
calculated by knowing the area of the tube that the meter is installed in.
Since you are probably trying to measure the cfm on you DC you don't want
to restrict the line much and that further limits you choices.
There are many methods for air flow measurement, but most of them are
pretty complex.
--
Lloyd Baker
"alexy" <[email protected]> wrote in message
news:[email protected]...
> "trs80" <[email protected]> wrote:
>
>>thanks. what is an ammeter?
>
> Given your moniker, I'll point you to this one:
>
> http://www.radioshack.com/product/index.jsp?parentPage=search&summary=summary&cp=&productId=2103173&accessories=accessories&kw=ammeter&techSpecs=techSpecs¤tTab=summary&custRatings=custRatings&sr=1&features=features&origkw=ammeter&support=support&tab=features
>
>
> --
> Alex -- Replace "nospam" with "mail" to reply by email. Checked
> infrequently.
"Morris Dovey" <[email protected]> wrote in message
news:[email protected]...
> trs80 wrote:
> | Is there poor mans CFM meter or a simple JIG one can rig up to
> | estimate the CFM being pulled by a dust collector through a 4 "
> | pipe?
>
> Try a Google group search on alt.solar.thermal for "Air Flow
> measurements".
>
> Inexpensive _and_ accurate.
>
> --
> Morris Dovey
> DeSoto Solar
> DeSoto, Iowa USA
> http://www.iedu.com/DeSoto/
>
>
Thanks for the tip Morris.
I'll have to take a look at that next week some time. I'm off to a living
history encampment for the scouts. Portraying the colonial carpenter again,
so science thought will be taking a back burner for the next 72 hours.
I am definitely interested in seeing any inexpensive and accurate methods
of air flow measurement, but then my definition of accurate may be a little
different. Also getting something calibrated, traceable to international
standards (a requirement in my line of work), adds cost.
--
Lloyd Baker
"trs80" <[email protected]> wrote:
>Is there poor mans CFM meter or a simple JIG one can rig up to estimate the
>CFM being pulled by a dust collector through a 4 " pipe?
>
>Maybe some sort of calculation based on the deflection of a known
>size/weight object at the measured opening diameter of the intake? Object
>might pendulum from top edge of opening.
>
>thanks
>
Any jig you can rig up will likely tell you relative CFM, but without
a way to calibrate it, you will only be able to tell whether you are
drawing more CFM from this port or that. If you use only one port at a
time, and ammeter on the line going to your DC may be just as useful
as a jig.
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.
[email protected] wrote:
>
> I remember a year or so ago when someone posted here that he'd found a
> fairly inexpensive wind meter, which he used at the end of the duct to
> measure the air speed, then used that to calculate CFM moving through
> the four inch tube.
Pilot and radio control hobby shops, as well as weather station dealers
sell "Kestrel" portable wind meters, like these:
<http://www.weathershack.com/portable-weather-stations.html>
"trs80" <[email protected]> wrote:
>thanks. what is an ammeter?
Given your moniker, I'll point you to this one:
http://www.radioshack.com/product/index.jsp?parentPage=search&summary=summary&cp=&productId=2103173&accessories=accessories&kw=ammeter&techSpecs=techSpecs¤tTab=summary&custRatings=custRatings&sr=1&features=features&origkw=ammeter&support=support&tab=features
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.
whats that have to do with airflow...lexy" <[email protected]> wrote in
message news:[email protected]...
> "trs80" <[email protected]> wrote:
>
>>thanks. what is an ammeter?
>
> Given your moniker, I'll point you to this one:
>
> http://www.radioshack.com/product/index.jsp?parentPage=search&summary=summary&cp=&productId=2103173&accessories=accessories&kw=ammeter&techSpecs=techSpecs¤tTab=summary&custRatings=custRatings&sr=1&features=features&origkw=ammeter&support=support&tab=features
>
>
> --
> Alex -- Replace "nospam" with "mail" to reply by email. Checked
> infrequently.
> [email protected] wrote:
>>
>> I remember a year or so ago when someone posted here that he'd found a
>> fairly inexpensive wind meter, which he used at the end of the duct to
>> measure the air speed, then used that to calculate CFM moving through
>> the four inch tube.
Come to think of it...
If all you want are relative measurements to judge improvement, it seems
there is an easy answer.
All you'd need is some sort of DC motor with a fan attached and a
digital voltmeter. The motor would probably need to have brushes, I'm
not sure if a brushless motor will work as generator. Make a fitting
with the fan in it to fit the duct, insert it into the air stream and
read the voltage produced. A higher air velocity will produce a higher
voltage.
Since the setup is not calibrated to any sort of standard, actual CFM
measurements would be impossible. However, the setup would tell you
"better or worse" as you make changes.