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.Terry McGee wrote: ↑Mon Jan 09, 2023 4:18 am 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.
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.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..."
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: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.....