Blowing machine

[Tunborough]

I'll wait till I hear your interpretation of the above before doing anything more!

I'd still like to see results from other calibrators with the longer tubing downstream of them, to see if they also line up the way the 30 x 4 calibrator does. After the dust settles from St. Patrick's Day, of course. Hope it's a good one for you.

[Terry McGee]

Yep, St Paddy's was great. A nice appreciative crowd, and everybody played well. And the management invited us back "anytime we like".

The small child of one of the musicians was amusing herself running around filming everything with her phone. The friend sent us a few seconds afterwards. We were me on flute/ whistle/guitar, Jesse on Hammer Dulcimer, Mark on box, Julie on keyboard and Matti on bodhran. The snippet was with me on whistle, my Tweaked Soodlums Mellow D. Guess who was loudest? Gulp, I need to be quietening whistles, not making them louder!

I'd still like to see results from other calibrators with the longer tubing downstream of them, to see if they also line up the way the 30 x 4 calibrator does.

OK. Pressure Regulator > resistor > flow gauge > whistle connector with PTO > calibrator-under-test > 130mm of 13.3mm tubing > air. Digital Manometer from PTO to air.

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Calibrators plus 130mm of 13.3mm tubing			
			
30 x 4mm Calibrator + 130mm of 13.3mm tubing to air			
Flow	MM(H20)	√A/P	Resistance
5	4	2.00	0.40
10	16.5	4.06	0.41
15	36.5	6.04	0.40
20	66.5	8.15	0.41
			
Average Resistance			0.40
			
			
30 x 2mm Calibrator + 130mm of 13.3mm tubing to air			
Flow	MM(H20)	√A/P	Resistance
5	60	7.75	1.55
10	271	16.46	1.65
15	623	24.96	1.66
20	1225	35.00	1.75
			
Average Resistance			1.65
			
			
5.18 x 10, 4 x 20 Calibrator + 130mm of 13.3mm tubing to air			
Flow	MM(H20)	√A/P	Resistance
5	3.5	1.87	0.37
10	14.5	3.81	0.38
15	31.5	5.61	0.37
20	58.5	7.65	0.38
			
Average Resistance			0.38
			
			
4.97 x 20, 4 x 10 Calibrator + 130mm of 13.3mm tubing to air			
Flow	MM(H20)	√A/P	Resistance
5	3	1.73	0.35
10	14	3.74	0.37
15	31	5.57	0.37
20	59	7.68	0.38
			
Average Resistance			0.37
			
			
5 x 10, 4 x 10, 2.9 x 10 Calibrator + 130mm of 13.3mm tubing to air			
Flow	MM(H20)	√A/P	Resistance
5	11	3.32	0.66
10	48	6.93	0.69
15	108	10.39	0.69
20	210	14.49	0.72
			
Average Resistance			0.69

[trill]

. . . The small child of one of the musicians was amusing herself running around filming . . . he snippet was . . .

Do you have it posted ? Can you give a link ?

[Terry McGee]

Fortunately not!

[Terry McGee]

A lady brought in two treble recorders yesterday, complaining that they seemed a bit dull and lifeless. Tapped out the blocks, and cleaned off the usual sticky breath condensate from the windway surfaces - the stuff that sticks our flute tuning slides together if we're not careful. But that wasn't the source of the lifelessness.

Turning to the bodies, I noticed that all the fingerholes appeared to be lined in thin brown felt. Now, nobody would do that, would they. On closer examination, it was slightly fluffy dirt. I can imagine an amalgam of dried bore oil, finger grease, domestic dust, hair, and fluff from the recorder mop. And although thin, keep in mind that recorder holes are small, to permit crossfingerings. And so recorders are naturally a bit on the underpowered side. Any additional losses are going to tell.

I used my trusty No 11 scalpel blade to scoop out the sludge, being very careful obviously not to dig into the underlying wood. And then repolished the insides of the holes with a fine abrasive cloth. Dramatic improvement - the instruments sounded stronger and brighter, and the owner was delighted.

So much so that she's going to bring another instrument next week. Her complaint with this one is that although clearly a well-made recorder, it requires "too much pressure". So I took windway measurements from one of yesterday's instruments, and will compare them to next week's. We may learn something from outside our usual range of inputs.

[trill]

. . .it requires "too much pressure". So I took windway measurements from one of yesterday's instruments, and will compare them to next week's. We may learn something from outside our usual range of inputs.

Any sign of roof + floor sculpting ?

Did you happen to glance at the blade ? And/or snap a pic ?

(flowmeter research still underway . . .)

[Terry McGee]

Any sign of roof + floor sculpting ?

Definite expansion in height in the middle of the windway, as we are used to seeing. But I didn't think to check whether any of that was a depression in the top of the block. I had the block out and could easily have put a rule along it to check, d'uh! My guess though is given the curvature is fairly shallow, it's probably just in the top of the windway.

Note my small diameter "feeler" drills tend to be pretty short, which is not a problem for treble whistles, but only gets me halfway on a treble recorder! Here are the numbers I was able to get.

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Coomber Treble		
L	H(L)	W
0	1.62	13.86
6.6	1.575	
15.85	1.53	
21.7	1.48	
31.7	1.375	
57.83	1	12

Did you happen to glance at the blade ? And/or snap a pic ?

No pics, but I certainly had a good look at it. I thought a pretty sharp ramp (ie small included angle). And undercut from below to form a pretty sharp edge. Maybe a slight protrusion of the block into the window space, but it would be no more than half a mm at most. And no dramatic chamfers on the top or bottom of the windway exit.

David Coomber was a pretty well-known and respected recorder maker in New Zealand, until suddenly he went off and became a psycho-analyst. I wondered what experiences with recorder customers might promote that kind of reaction, and the urge to go delving deep into damaged minds.....

[Terry McGee]

Then I'd like to try a similar test on the Feadog Mk 1 and the old Generation whistle heads with and without the whistle tube plugged into the whistle head, again at 5, 10, 15, 20 L/min.

OK, herewith the Old Gen. You didn't specify holes open or closed, so I did both. And, being a suspicious old B....., I repeated the Head only afterwards.

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Old Gen head to air, 20 March 23							
Flow	Head	Res.	Close	Res	Open	Res	Head rpt.	Res.
5	7	0.53	7.5	0.55	7.5	0.55	8	0.57
10	30	0.55	29	0.54	29	0.54	30	0.55
15	65	0.54	63.5	0.53	63.5	0.53	65	0.54
20	117.5	0.54	113.5	0.53	114.5	0.54	118.5	0.54
								
Average Res.	0.54		0.54		0.54		0.55

[Terry McGee]

And while I had Old Gen plugged in, I thought I'd see what the effect of Shutting the window and Plugging the tube socket would be. (Not at the same time of course!) Shutting the window involved carefully laying insulating tape over it to close off the escape of air without pushing the tape down onto the ramp. Plugging the tube socket involved a rubber bung.

Preceded by the Head only readings again, taken afresh to test repeatability.

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Old Gen head to air, 20 March 23						
Flow	Head	Res.	Shut	Res	Plug’d	Res
5	8	0.57	7.5	0.55	8	0.57
10	30	0.55	30.5	0.55	31.5	0.56
15	66	0.54	69	0.55	70	0.56
20	118.5	0.54	125	0.56	129	0.57
						
Average 	0.55		0.55		0.56

So we are seeing a bit of a pressure rise in both cases, but not dramatic.

[Terry McGee]

And now for the Feadog Mk 1. Head only, tube with all holes covered, tube with no holes covered.

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Feadog Mk1 head to air, 20 March 23						
Flow	Head	Res.	D	Res	c#	Res
5	5	0.45	5	0.45	5	0.45
10	18	0.42	18	0.42	18	0.42
15	40	0.42	39	0.42	39	0.42
20	71.5	0.42	70	0.42	69	0.42
						
Average 	0.43		0.43		0.43

[Tunborough]

With the flowmeter below the 30 x 4 calibrator, the pressure/flow relationship was pretty much entirely explained by Bernoulli and pressure loss through the calibrator. With the calibrators opening directly to air, it took an adjustment of Ke = 0.35 or so to get the flow/pressure relationship to line up. With the tubing below the calibrators, the adjustment was less, but still there, Ke = 0.12. The latest numbers don't agree with earlier measurements on similar configurations. Has something changed since the earlier measurements. Is the weather still hot there?

Here are some of the values for the adjustment, Ke:

Earlier tests with calibrators open to air: Ke = 0.35
Earlier test with Feadog Mk 1: Ke = 0.35
Earlier test with old Gen, flows from 6 to 20 L/min: Ke = 0.13
Calibrators followed by 130 mm tubing: Ke = 0.12
Old Gen head only: Ke = 0.25
Old Gen with tube: Ke = 0.20
Feadog head only: Ke = 0.43
Feadog with tube: Ke = 0.40

It's interesting to see that, as with the calibrators, having a tube below the windway of the old Gen did reduce the pressure. Not so much on the Feadog, however. This suggests that calibrator + tubing may be more like a whistle than the calibrators alone. Unfortunately, we still don't have a consistent value for Ke.

[david_h]

Calibrators followed by 130 mm tubing: Ke = 0.12

Is all the calibrators giving the same Ke? So you have the pressure loss down a calibrator modelled adequately? I may have missed that earlier.

[Terry McGee]

The latest numbers don't agree with earlier measurements on similar configurations. Has something changed since the earlier measurements. Is the weather still hot there?

No, it's cooled down a lot, thank goodness. But I'm not convinced the weather is the culprit. I suspect it's more to do with the Flow Gauges or possibly the plumbing from them to the Whistle Connector. Because we were only dealing with flows up to 20L/Min, I had disconnected the T-joiners that feed the RH Flow Gauge. We get a clue about this in the earlier results, see first group below.

But to be sure, I re-ran the last test this morning using just the LH Flow Gauge, then started plumbing in the RH gauge. You can see (lower group of data) that splitting the feed to the Flow Gauges didn't change anything, but inserting a T joiner to allow both to feed the Whistle Connector did change the pressure a little, even though the RH gauge was still isolated. Opening up the RH gauge made a bigger change, although that could be due to a number of causes, eg gauge errors, resolution problems, etc. Finally, I removed my passive "resistor" feeding the gauges and reinstituted the Flow Regulator. That made no further difference. This all seems to confirm my assertion that changes upstream from the Flow Gauges are not significant. But that changes downstream, even if seemingly minor, can be.

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Earlier Old Gen results			
20	103	0.507	Old Gen head after Flow Meters in parallel, 12 March 2023: 
20	119.5	0.547	Old Gen head after Flow Meters singly, 12 March 2023: 
20	118.5	0.54	Old Gen head to air LH Flowmeter only, 20 March 23
			
Old Gen head after LH Flow Meter, 21 March 2023: 			
20	118	0.54	Old Gen head after LH Flow Meter only
20	118	0.54	Split feed to both flow meters, but RH blocked at output
20	114	0.53	Insert T-joiner to combine output of 2nd flow meter, but with 2nd isolated 
20	105	0.51	Both flow meters in, 2 x10L = 20L
20	105	0.51	Flow Controller reinstated between Pressure Regulator and Flow Gauges instead of passive resistor.

Are those changes enough to explain the variations you are getting?

I'm using the T-joiners that are made for this kind of tubing. They have two obvious weaknesses:
- they reduce the 6.35mm bore of the tubing to about 4.75mm in the couplers
- they introduce one or more right angle bends, depending on how deployed.

If we could confirm that they are part of the problem, I could look at making up a Y connector that doesn't involve loss of diameter.

[Terry McGee]

So, I decided to do just that, shortening the tubing from the Flow Meters to the Whistle Connector, and replacing the internal T-Joiner with an external T-Joiner that widens the bore at the junction rather than narrowing it. No other changes.

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Old Gen head after reducing connector resistance, 21 March 2023: 			
20	116	0.54	LH gauge
20	106	0.51	Both gauges

But still seeing a change in pressure when the second gauge is brought in.

Wouldn't it be awful if we had to concede that trill was right, that we might need a single better flow gauge....

Any other suggestions I should try?

[david_h]

I haven't been plotting the numbers because I haven't been keeping track of the changes to the setup and I am not sure what factor Tunborough has successfully incorporated into his model.

My thoughts are:
- If measurements between 5 l/min and 20 l/min are enough for the derive the model just use one flow meter. May need them both when it comes to using the model but cross that bridge later.
- is the upper PTO far enough away from the whistle/calibrator connector that pressure losses just outside the windway entrance are not missed? (does moving it make a difference?)
- is the upper PTO so far away from the whistle/calibrator connector that pressure losses in the tubing need to be included in the model? (ditto)
- have the small volume differences due the changing pressure at the flow meter been taken into account (or calculated to be too small to worry about) ?
- are there any indications that the flow meter scale in non-linear? I think everything in the model has a linear Flow-sqrt(Pressure) relationship so the resistances should be the same for all pressures.**

I think identifying the influence of changes beyond the windway exit is real progress.

Would putting something to generate an edge tone (so with no resonator in place) beyond the calibrator exit give some glimpse of what the jet velocity was doing? Or is that just too complicated to interpret?

** there are results from Q and P measurements on all members of a consort of recorders on pages 9, 10 and 11 of the paper linked on this page https://www.researchgate.net/publicatio ... of_the_Jet (can't link the PDF directly). Apart from the odd wayward point nothing to indicate any change in the mechanism of flow over the range of an instrument. Figure 1 on page 3 suggests that a curved floor and roof of the windway is standard on a recorder. I think that suggests that oddities in Terry's data (variable resistance on one whistle) are probably due to the flowmeter and maybe some sort of correction could be worked out. That's what I suggested the zero length calibrator for but if Tunborough has the modelling of the calibrator windways sorted out it may not be needed.