Blowing machine

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Tunborough
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Re: Blowing machine

Post by Tunborough »

Terry McGee wrote: Sat Feb 04, 2023 12:27 amDo you still have aspirations to build a blowing machine, Tunborough, in which case should we return to answering the question "how"?
Absolutely. I would like to make measurements on whistles that I have in-hand, varying window length and other dimensions as feasible.

Since I don't have a compressor in the back room, or even in the budget, I'm looking at other options. High volume, low pressure (HVLP) equipment might be an option, but they have much higher volume and pressure than I need, 10 CFM and up, rather than zero to more like 3 CFM. From the back of a closet, I pulled out an air bed inflator, but I think it, too, is much higher volume (and higher noise) than I need. Maybe I should be looking at hairdryers, if I can find one quiet enough.
trill
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Re: Blowing machine

Post by trill »

Here's a flowmeter:

https://www.amazon.com/TOPCHANCES-Porta ... B082HM27J5

No computer or software needed. Just batteries.

I've seen lower priced units, medical grade, but a laptop+software were needed.

A meter like this, plus a downstream manometer, and we're set to quantify the backpressure+flow of any whistle on your test-rig.
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Terry McGee
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Re: Blowing machine

Post by Terry McGee »

Tunborough wrote: Sat Feb 04, 2023 10:38 am
Terry McGee wrote: Sat Feb 04, 2023 12:27 amDo you still have aspirations to build a blowing machine, Tunborough, in which case should we return to answering the question "how"?
Absolutely. I would like to make measurements on whistles that I have in-hand, varying window length and other dimensions as feasible.

Since I don't have a compressor in the back room, or even in the budget, I'm looking at other options. High volume, low pressure (HVLP) equipment might be an option, but they have much higher volume and pressure than I need, 10 CFM and up, rather than zero to more like 3 CFM. From the back of a closet, I pulled out an air bed inflator, but I think it, too, is much higher volume (and higher noise) than I need. Maybe I should be looking at hairdryers, if I can find one quiet enough.
What about using the airbed inflator to fill the airbed, then shut it off, like my compressor fills its tank and shuts down. Via a manual or one-way valve so you don't have to keep unplugging and plugging the pump from the bed? And load weights onto the airbed to create the pressure you need to create the flow you want? Some kind of in-line tap to conserve the air and control the flow, flow meter to measure the flow and a home-made U-tube Manometer to measure pressure when needed?
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Terry McGee
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Re: Blowing machine

Post by Terry McGee »

Heh heh, I have something rather silly to report! It occurred to me during the night (when I seem to do my best work, arguably my only good work!) that I've only been reading only half the U-tube manometer. When there is no pressure applied, the left and right arms have equal levels of liquid. When you apply some air pressure, it depresses the level on the input side and the level on the output side rises by the same amount. The difference between those two levels is the correct measurement for that applied pressure. I'd stupidly been recording only the change in level on one side (easier to measure - you don't have to keep moving the rule.). So double any pressure readings I've reported up to this point.

I'll just go down to the workshop and beat myself repeatedly over the head with the 6 pound demolition hammer I keep for such occasions.....
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Terry McGee
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Re: Blowing machine

Post by Terry McGee »

trill wrote: Sat Feb 04, 2023 4:43 pm Here's a flowmeter:

https://www.amazon.com/TOPCHANCES-Porta ... B082HM27J5

No computer or software needed. Just batteries.

I've seen lower priced units, medical grade, but a laptop+software were needed.

A meter like this, plus a downstream manometer, and we're set to quantify the backpressure+flow of any whistle on your test-rig.
Now that one only reads up to 10mL/Min whereas we are seeing flows up to around 40L/Min (admittedly hammering the poor old whistle harder than the maker intended!)
Last edited by Terry McGee on Sat Feb 04, 2023 11:10 pm, edited 1 time in total.
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Terry McGee
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Re: Blowing machine

Post by Terry McGee »

Tunborough wrote: Wed Feb 01, 2023 7:36 am . . .you might want to check this by (on one whistle * ) measuring air flow and pressure over a wide range, and plot air flow and the square root of air pressure to see if you get a straight line that goes through zero.
OK, a bit of progress to report here. I've done this test on the Feadog Mk 1 at four flow rates (0, 10, 20, 30, 40 L/Min), and graphed the square root of air pressure as Tunborough had suggested. Sure enough, I get a straight line that goes through zero. Well, straight within the limitations of the measurement technology, but no question.

I did the first test with all the finger holes uncovered (OOO OOO). Then repeated it with all the holes covered (XXX XXX). No significant changes. So did the same test again having removed the fingering tube from the head. No significant changes. Tried covering the window, pressure went up very slightly, flow remained the same.

So then I repeated the test with the thin-windway Killarney. Stupidly applied the 40L/min flow which was still set up from the previous test. Far too much flow for the Killarney, so the dramatically increased back-pressure shot the blue manometer liquid out the top again. Fortunately didn't make it to the ceiling this time. Moral of the story, always reduce flow to zero between models! Refilling the manometer and proceeding more carefully, I found I could only get this one up to 30L/Min. A taller U-tube Manometer could push it further, but I think this is plenty, so I've now made that the limit on the testing.

So then repeated the test with the large windway Tweaked Mellow D. It required a little more pressure than the old Feadog to achieve the same flow. Or, if you'd prefer to look at it the other way around, the same flow generates a little more back pressure. But nothing compared to the Killarney.

Looking at the back pressure of all three, at 30L/Min flow rate (so we can include the Killarney) we find they are:
Killarney: 340mm H20
Tweaked Mellow D: 170mm H20
Feadog Mk 1: 134mm H20

Regard these as interim results for the time being. Making sure all these funny-shaped beaks can form an airtight seal with the tubing feeding it is quite a challenge, and of course any leakage here is fatal to accuracy. I'd like to come up with a better attachment system. It would then be wise to at least spot check the findings.

I did also try what happens if you don't have any whistle connected. I thought it might give me a figure for the resistance of the tubing below the point where the Manometer is connected. But I got negative results - the level dropped a few mm. M. Bernoulli messing with me, I suspect.

We can say safely that the pressure needed by a whistle to set up a certain flow (and thus airspeed) is a windway thing, and unrelated to things going on from the window downwards. Presumably, we could assign each model of whistle with a value for its resistance. Measured in MM H20/L/Min or some similar unit? And presumably we could check that value against predictions we might make by measuring the windway length, height, taper, etc of the whistle.

It also probably means we can leave off taking pressure readings while investigating regime boundaries etc, as they can be calculated from the flow readings, using the resistance value mentioned above. That would speed up the regime readings.

One source of minor error I noticed is the tendency for the last of the liquid in the manometer to take a while to come back down the tube and rejoin the body of liquid after a high reading. But it's pretty minor.
trill
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Re: Blowing machine

Post by trill »

Terry McGee wrote: Sat Feb 04, 2023 9:22 pm. . . only reads up to 10mL/Min whereas we are seeing flows up to around 40L/Min . .
This one goes to 100 l/m: https://www.amazon.com/dp/B0B5GJX2HL
trill
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Re: Blowing machine

Post by trill »

Tunborough wrote: Sat Feb 04, 2023 10:38 am. . . hairdryers, if I can find one quiet enough.
Some ideas:

1) Mount the hair dryer in a box or in a different room, with a hose/duct to feed your test-bench. That would keep the noise out of your test area.

2) For in-stream noise, maybe run the duct into a "muffler" or plenum to dampen the acoustic flow noise.

3) Here's a quiet fan: https://www.amazon.com/dp/B075333HWM/
trill
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Re: Blowing machine

Post by trill »

Terry McGee wrote: Sat Feb 04, 2023 11:06 pm. . . a bit of progress to report here. . .
Terry McGee, down in Malua Bay
Gives us new data almost every day !
He's fast, he's quick, he's got his own shop
Here's hoping u-tube geysers wont make him stop !

:)
trill
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Re: Blowing machine

Post by trill »

Terry McGee wrote: Sat Feb 04, 2023 11:06 pm... shot the blue manometer liquid out the top again. . .
:shock: :love: :thumbsup:

Sir, having worked in a shop myself, I know exactly the feeling.

Best laugh I had all day !

:)
trill
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Re: Blowing machine

Post by trill »

Terry McGee wrote: Sat Feb 04, 2023 11:06 pm Looking at the back pressure of all three, at 30L/Min flow rate (so we can include the Killarney) we find they are:
Killarney: 340mm H20
Tweaked Mellow D: 170mm H20
Feadog Mk 1: 134mm H20
Behold !

The first compilation of it's kind !

One thing though: we don't know what "tones/notes" those flows correspond to.

So, Terry, I'd like to propose a related test: for the same 3 whistles, pick a single note (e.g. G) and find the flow + pressure that puts the pitch-needle dead-on.

That table of data would be shed some light on "backpressure" as experienced by a player.
Last edited by trill on Sun Feb 05, 2023 2:56 am, edited 1 time in total.
trill
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Re: Blowing machine

Post by trill »

Terry McGee wrote: Sat Feb 04, 2023 9:19 pm The difference between those two levels is the correct measurement . . . So double any pressure readings I've reported up to this point.

I'll just go down to the workshop and beat myself repeatedly over the head with the 6 pound demolition hammer I keep for such occasions.....
Sir, we've all been there !

Thank you for explaining. :)
trill
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Re: Blowing machine

Post by trill »

Terry McGee wrote: Sat Feb 04, 2023 11:06 pm. . . a value for its resistance. Measured in MM H20/L/Min or some similar unit?
Yes, I agree.

I have a vague memory of something called a "discharge coefficient" for flow. It involves knowing the pressure drop, flow area, and actual (measured) flow.

I'll do some digging and see if I can get more specific. More when I get to it. . .
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Terry McGee
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Re: Blowing machine

Post by Terry McGee »

trill wrote: Sun Feb 05, 2023 2:27 am
Tunborough wrote: Sat Feb 04, 2023 10:38 am. . . hairdryers, if I can find one quiet enough.
Some ideas:

1) Mount the hair dryer in a box or in a different room, with a hose/duct to feed your test-bench. That would keep the noise out of your test area.

2) For in-stream noise, maybe run the duct into a "muffler" or plenum to dampen the acoustic flow noise.

3) Here's a quiet fan: https://www.amazon.com/dp/B075333HWM/
Fans tend to be pretty low on pressure, and as we've seen from today's pressure vs flow tests, we need a bit of pressure for those thinner windway whistles. Our box player tunes accordions, and for that purpose put together a blower capable of playing pairs of accordion reeds. It was based on the blower from an old 12volt car portable vacuum cleaner, set in a box which acted as plenum (to smooth the flow) and sound insulation (so it didn't mess with his tuner). Vacuum cleaners need flow and pressure (suction). He provided it with a 0-12V adjustable power supply to be able to control the amount of pressure. (Being a free-reed instrument, we're talking pressure-driven, rather than flow-driven.) That could be a possible approach. The box containing the blower could even be left in the next room, with the supply tube and control lines taken under the door, to further help reduce noise contamination.
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Terry McGee
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Re: Blowing machine

Post by Terry McGee »

trill wrote: Sun Feb 05, 2023 2:40 am So, Terry, I'd like to propose a related test: for the same 3 whistles, pick a single note (e.g. G) and find the flow + pressure that puts the pitch-needle dead-on.

That table of data would be shed some light on "backpressure" as experienced by a player.
But where the pitch-needle is dead-on depends on how far I have the finger tube pulled from the head! But I could tune them to where I would play that note in tune and see what that yielded....
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