And, Hans, what in your experience constitutes “a good chamfer” on a High D whistle? Say 1mm of chamfer, at around 45º? And left as the angle, or any smoothing of either or both of the transistions?
And what do you think the block protrusion actually does, in physical terms? I’ve seen it often as a regular feature of recorders, but can’t bring to mind any explanations of what’s actually going on there. Any thoughts?
Heh heh, coming to my mind is a totally adjustable whistle head, with dozens of little thumbscrews and wheels for stopper protrusion, windway width, windway height, window height, ramp angle, window length, etc, etc. You probably wouldn’t be able to lift it unaided…
“Quick nurse, McGee is out of his bed again, and heading for the workshop…”
Ahh, I wrote “good chamfer” so I don’t need to commit to particular measurements! I mainly followed the tradition I observed in the shape of various well-built whistles, and not using a lower chamfer did not help. For a high D whistle I like to set the window to 8mm width, and 4mm length (from labium to upper windway exit), with the block having about 3.5mm distance to the labium, so it protrudes 0.5mm. The chamfer filed on it would be between 45 and 60 degrees, say. I preferred it a bit steeper than 45, and not cut too much off at the windway floor. The cutoff should not be more than the protrusion, perhaps even a little less. I always smooth any edges. Perhaps a totally rounded chamfer may work as well, I don’t know.
And what do you think the block protrusion actually does, in physical terms? I’ve seen it often as a regular feature of recorders, but can’t bring to mind any explanations of what’s actually going on there. Any thoughts?
I don’t know, my acoustical physics is not good enough. I imagine it plays a role in unbalancing the air stream. I hoped you could tell me! Most makers use it, both for straight and for curved windway designs. Terry, for what I can read in this thread, you have not delved into the difference of straight versus curved windway and labium. I think there are acoustic differences, and to me a curved windway/labium will produce a somewhat rounder tone.
Heh heh, coming to my mind is a totally adjustable whistle head, with dozens of little thumbscrews and wheels for stopper protrusion, windway width, windway height, window height, ramp angle, window length, etc, etc. You probably wouldn’t be able to lift it unaided…
And add to that windway curvature…
The problem with the “fully adjustable head” is that it cannot guarantee a fully smooth air stream, there are too many edges in such a machine, and that influences the tone.
And of course this also needs a blowing machine, where you can adjust and measure pressures and air volume and speed…
And what do you think the block protrusion actually does, in physical terms? I’ve seen it often as a regular feature of recorders, but can’t bring to mind any explanations of what’s actually going on there. Any thoughts?
I don’t know, my acoustical physics is not good enough. I imagine it plays a role in unbalancing the air stream. I hoped you could tell me! Most makers use it, both for straight and for curved windway designs.
Would this be a feasible enough explanation, Hans, others? Having the block protrude a little into the window area helps force the returning pressure wave upwards earlier, lifting the jet out of the window to start the next halfcycle?
And perhaps chamfering off the end of the block restores the full length of the window to the airjet, stopping the edge of the protruding block from impeding the airjet on its downward cycle? Giving the jet permission and room to go down, but not actually forcing it to go down? Anyway, perhaps we simple whittlers and carvers don’t need to know the gory details, just have faith?
Terry, for what I can read in this thread, you have not delved into the difference of straight versus curved windway and labium. I think there are acoustic differences, and to me a curved windway/labium will produce a somewhat rounder tone.
Hmmm, you raise a good point there, Hans. And it applies also to the Comparison of High D whistle bores listing. The inclusion of (curved/straight) or (curved/flat?) would enable readers to say: “I like the robust sound of big-bore flat-blade whistles, what are my options in that area?” or “I prefer quieter, more economical sweet-sounding curved blade whistles, so what’s available there?”
But I wonder if flat windway whistles have rather given way to curved, just because the curved ones are easier to make using round tube, unless perhaps when using the moulded plastic head approach?
It’s been a long time since I’ve paid attention to trends in recorder making. If block protrusion is now a regular design feature, it became so in the meanwhile. Can you point me in the direction of a few examples?
…what…constitutes “a good chamfer” on a High D whistle? Say 1mm of chamfer, at around 45º? And left as the angle, or any smoothing of either or both of the transitions?
Again speaking from back in the day and with regard to recorders, chamfering is a core aspect of the voicing process. As such, it is adjusted by ear not measurement. It’s easy enough to set numbers on the block chamfer for a good first approximation. The upper chamfer (the one at the end of the roof of the windway and significantly smaller) is another matter. It is crucial to getting a recorder comfortably into the third octave but is tricky enough to see, much less measure. I’ve been party to many discussions about how to address the latter detail when documenting historical instruments. The way I understand it, the effect of chamfer benefits from clean faceting. I’ve read descriptions of it being added to assembled whistles by rubbing sandpaper across the end of the windway but have a rough time imagining that clear-cut chamfers would be less purposeful.
I wonder if flat windway whistles have rather given way to curved, just because the curved ones are easier to make using round tube, unless perhaps when using the moulded plastic head approach?
In historical practice, recorder windways were arched both axially (roof only) and radially — and tapered in width to boot. I regret not having examined how this mapped into flageolet design while I had access to an extensive collection of both instruments. The present discussion lies on the same continuum and I’m curious to see where it leads.
That may indeed an important reason, it certainly was a reason to start me into whistle making. But the historic traditional tin whistle had a flat windway, and a simple design too. So has the modern equivalent, the Overton. But it needs some good machinery to squash the round alu tube into a square shape for the head. But this then gives the advantage of bore restriction in the head, and thus helps the octave tuning!
I have been using a tapered windway for all my whistles, I reckoned that a slight taper would lead to a smoother air flow, with less resistance from the walls.
Hmmm, I think I’d bow to your greater experience in the field. I’m sure I’ve seen it, but that could well be in instruments brought in for repair or attention. I don’t think we see much sign of protrusion in whistles either, do we? The windways on all the plastic ones I’ve seen definitely stop dead at the window. The most obvious block protrusion I can visualise is on the classic Clarke whistles. And there it is so obvious, the first time I saw one I assumed something had gone wrong in the making. Here’s a reminder, taken from their website. Note, no noteworthy chamfer:
I regard Shaw whistles as truer instantiations of Clarke’s putative initial innovation than the eponymous ones now are. I have three Shaw whistles at hand; high D, C, G in descending order. They were selected out of a batch at Waltons on George’s Street in Dublin fifteen years ago, when side-by-side testing was both permitted and encouraged. There’s no body chamfer on them, which I wouldn’t expect on any instrument rolled from thin sheet metal. The blocks have no chamfer either but their lower ends are cut on a bias, roughly paralleling the one that forms the beak but at a less acute angle to the axis of the bore.
The edge of the inner end of the block on the windway side underlaps the upper edge of the window. The edge of the block opposite the window protrudes into it by well over half of the window’s length. I have no idea if the position of the block or the bias of its inner end were deliberately adjusted during the tuning and voicing processes. However, changing overlap/underlap ought reasonably to have an effect similar to adjusting chamfer — and the angled inner end of the block can also be seen as a steep non-faceted chamfer.
ETA: I’m now taking closer looks at other whistles in my arsenal from the perspective of the present discussion. I note that Phil Hardy extends the block into the bore on many, if not all, of his models by the width of the chamfer or just slightly less. I picked up a range of Chieftains on the same visit to Waltons and will write more about this aspect of their design in comparison with his later models separately, after the iterative dig through the remaining whistle heap.
Interesting stuff, stringbed. If I understand correctly, in some of these you are saying that the entire inner face of the block slopes, with the top (under the windway) starting before the end of the windway, but with the bottom of the block protruding significantly into the windway. An extreme and steep chamfer, if you will.
I’ve wondered about that approach, from the perspective of what happens to the returning pressure wave front as it approaches the back of the stopper. Just slams into it, and then looks around for a way out of here? “Hmmm, I’m going to have to shove that pesky air jet out of my way…”
What would happen if we gave it some help and guidance? A slope at the back of the block as I think you’ve described to redirect it upwards? Or would it be better to offer it a curved (concave) slope to coax it around the corner and help it redirect its energies into shoving airjets rather than generating heat? Or am I fantasising and anthropomorphising?
We could probably test these questions by sticking shaped block extensions into the back of flat-blocked heads…
It’s times like this I miss the late (Prof) Neville Fletcher. If asked, he would think for a moment and then say: “I’m reminded of some work a student of mine did up at the University of Armidale. We found that…”
And thinking, Tunborough, that we are now transgressing from acoustics into aerodynamics, so maybe the WID model can’t help us here? Feel free to shoot me down in flames…
I have been holding my breath, and realise that it may be the wrong thing to say in the company of craftsmen and engineers, but would a 3D printer have roll here. It might not make finely tuned whistle heads but one change at a time would be possible. Results could be hooked up to the blowing machine.
Correct. On all my Shaw whistles, the surface of the block that forms the floor of the windway ends just a smidge short of the end of its ceiling. The surface of the block that delimits the upper end of the air column is not perpendicular to its axis and slopes to a point opposite the middle and lower end of the window.
I’ve wondered about that approach, from the perspective of what happens to the returning pressure wave front as it approaches the back of the stopper. Just slams into it, and then looks around for a way out of here? “Hmmm, I’m going to have to shove that pesky air jet out of my way…”
The air reed and air column form a coherent oscillating system. I can’t see how the one component can, much less need to, exert force counter to the other. Additionally, the Shaw whistles are strongly tapered. On the high D one, the area of the window is 25% larger than that of the bell. If the vibrating air column were detrimentally constrained by the upper aperture, it would be even more so by the lower one. We would then be looking at a good reason for reducing the taper. For reference, the area of the window on a comparable but cylindrical Generation is 5% larger than than the cross-sectional area of the main bore.
What would happen if we gave it some help and guidance? A slope at the back of the block as I think you’ve described to redirect it upwards? Or would it be better to offer it a curved (concave) slope to coax it around the corner and help it redirect its energies into shoving airjets rather than generating heat? Or am I fantasising and anthropomorphising?
Many musical instruments take offense at being anthropomorphized (ask any so-called “baby grand” piano) but we should be able to avoid that risk here. And rather than speculate about the internal aerodynamics of a whistle perhaps we can stipulate a workshop rule of thumb that is amenable to informal assessment. The one here would be that any detail in a whistle’s structure that may potentially cause undesirable turbulence is worth trial modification. This is well instantiated by the suggestion that:
We could probably test these questions by sticking shaped block extensions into the back of flat-blocked heads…
I reckon once we can crack whistle (and flute) computer modelling, 3D printing should have great potential at least in prototype development. But I don’t see the likes of me getting that far. We have to leave something for the next generation to do!
Interesting to look back on the last 50 years. When I started making, there were no wooden flutes being made apart from those by a few baroque-flute makers, and just a few whistle makers, all well-established names. Look now at the C&F lists of flute and whistle makers!
Pretty much all of what has gone before was achieved through experimentation and selection - acoustic theory has not played a big role. That’s where I’d be looking for the next big developments.
Do you mean modelling as in CAD, or modeling as in simulating fluid dynamics? Because I do the first, and I know the 2nd is possible… I just can’t figure out how to get my model into this program: https://sim-flow.com/
All of my whistleheads start out 3D printed, and I finish the windway floor, ceiling, exit face, and airblade with needle files and sandpaper. Less cleanup / voicing is required on resin printed whistles, but adjusting the critical surfaces and edges is still essential. I don’t resin print production models simply because there’s no way to make them look nice/maintain durability.
At this point I bet it’s quicker to feed sound samples and a CT scan of the instrument into a machine learning program (aka AI) and have it predict what a flute producing a desired tone would sound like. It may not give the causal information regarding the impact of the design features, though. I don’t know enough about ML to say whether it’s possible to look ‘under the hood’ for a program like that.
Thanks for the comments on the whistle anatomy illustrations. I drew those up for my “Whistle Makers Anthology Book” many years ago to help fill a void in information at the time.
Hello Terry,
I used to take for each tonehole a value that I called “cutoff ratio”, which is the Tonehole’s Local Cutoff Frequency divided by the Tonehole’s Frequency. Then by graphing in the Excel the Frequency vs the cutoff ratio I would try to make the toneholes have a linear progression of this ratio from low to high. That helped predict more “sound alike” tonality from one hole to another.
The problem with cut-off ratio is the logarithmic nature of frequency. This makes cutoff ratio naturally climb as frequency got higher. Maybe some math wiz develop some antilog function to make this relate each hole from a a flat line perspective. Then the peak to peak of these ratios would give you an overall “Q” factor (like they do with RF coil quality) that would predict the performance of a set of toneholes.
Sorry about the delay. I used Arthur Benade’s formulas.
I stopped making instruments in 2020 due to numbness in fingers from a nerve pinch in the neck.
=34500*(Tone Hole 2b)/(Bore Dia at Tonehole 2a)/2/PI()/SQRT((Eff Chimney Height)*(Tone Hole 2S))
Now note: The value 0.6133 is the industry standard for the efficiency of a hole with a 90 Deg edge. If your toneholes edges in the bore are rounded or chamfer then this efficiency will change.
If you have good repeatable manufacturing habits then you can fine tune this factor by testing on instruments you’ve already made. This will help you to predict future instruments in similar keys because you are using repeatable tonehole geometry.
I learned about this factor this from my day job where we work with with orifice plates in air flow measurement, ANSI Specification ANSI-MFC-3M. This factor will also change when the bore radically varies ratiometrically from the tonehole diameter from what you have done in the past. Industries have been using such formulas for many years for predicting flow through holes.
Another factor is “End Correction”, this deals with how much air column blows out of the end of the whistle before it is resisted by contact with the atmosphere. Again, based on manufacturing habits of chamfer or taking the edge off of the hole this factor can vary from 0.5 to 0.75. I always used 0.6133 for this as well.
