Penny or Irish Whistle

Introduction

This lesson is derived from a project by Jay Brockman, Associate Dean of Community Engagement and Experiential Learning and Associate Professor in the department of Computer Science and Engineering and department of Electrical Engineering at the University of Notre Dame.

Penny or Irish whistles work because a vibrating stream of air resonates inside a tube of a given length which produces sound waves at a given pitch. What distinguishes a penny whistle from other types of flutes is its use of a fipple to produce the vibrations. A fipple is a type of mouthpiece where a stream of air is blown through a channel and cut by a blade. This structure allows a thin sheet of air to pass beneath the blade. The fipple makes it easy for the player to set up the vibrations, but gives the player less control over shaping the note. Below is an animated GIF of a fipple producing vibrations:

The pitch or frequency of the note produced by a whistle depends on the tube length. Shorter tubes produce higher frequencies because the frequency is proportional to 1/(tube length).

By drilling holes into the tube, you shorten the tube, which raises the pitch. By strategically placing the holes and covering them with your fingers, you can create an instrument that can play the notes of a scale. A traditional Irish Penny Whistle has 6 holes tuned to play a D major scale.

Materials

• 1 piece of 1/2" schedule 40 PVC 240 mm long
• Drill bits less than or equal to 1/8"
• A hand drill
• A 3D printer

Fusion 360

1. Create a New Design and save it.
2. Create a Sketch:
   
3. Select the ground plane:
   
4. Select Polygon→Inscribed Polygon :
   
5. Create a hexagon at the origin that has a radius of 14mm:
   
6. From the Sketch Palette, enable Horizontal/Vertical:
   
7. Click on the bottom of the polygon to straighten the alignment:
   
8. Stop the Sketch:
   
9. Extrude the profile 25mm:
   
10. Create a new Sketch:
    
11. Select the top of the extruded hexagon to work on:
    
12. Either select Offset from the Sketch menu or type o to enable Offset:
    
13. Click on the the polygon and type -4:
    
14. Either select circle form the Sketch menu or type c and create a circle at the origin that has a diameter of 21.7mm:
    
15. Stop the Sketch.
16. Extrude the hexagon -23mm:
    
17. Turn the sketch back on:
    
18. Extrude the circle -10mm:
    
19. Create a new Sketch:
    
20. Select this plane (the one perpendicular to the blue axis):
    
21. Either select rectangle from the Sketch menu or type r and create a 8x12 rectangle:
    
22. Either select Sketch Dimension from the Sketch menu or type d to enable it. Measure the distance between th bottom of the hexagon and the bottom of the rectangle and set it to 2:
    
23. Enable Sketch Dimension again and measure from the side of the rectangle to the side of the plane. Set the dimensio to 3:
    
24. Stop the Sketch:
    
25. Extrude the rectangle -4mm:
    
26. Create another new Sketch:
    
27. Select the side of the cut you just made:
    
28. Adjust the view:
    
29. Either select Line from the Sketch menu or type l and draw a 8mm vertical line from the far top corner of the plane:
    
30. With Line still active, draw a diagonal line connecting the end of the vertical line to the near top corner of the plane:
    
31. Stop the Sketch:
    
32. Extrude the triangle 8mm:
    
33. Change the view so you can see the bottom and create a new Sketch:
    
34. Select the Bottom to be the plane:
    
35. Select the line command and create a small line from the midpoint. This vertical line should be 2.2mm:
    
36. Convert the line to a construction line by selecting it and then enabling Normal/Construction from the Sketch palette:
    
37. Draw a rectangle 4mm x 2 mm:
    
38. From the Sketch menu select mirror:
    
39. Select three edges of the of the rectangle:
    
40. Select the rectang;es edge that aligns with the vertical line as the mirror line:
    
41. Complete the transform by clicking OK:
    
42. Type t for trim and click on the center line to remove it:
    
43. Select the 3 point arc from the Sketch menu:
    
44. Create a 3 point arc:
    
45. Stop the Sketch:
    
46. Extrude the rectangle -2mm:
    
47. Turn on the last Sketch:
    
48. Extrude the arc 20mm:
    
49. You should have something like this:
    
50. Modify the exterior by adding text (do not extrude more than 1mm):
    
51. Or add some fillets:
    
52. Export and print!

Assembling your Recorder

1. Start with a tube cut to 240 mm (9 7/16 inches). Use 1/2" schedule 40 PVC tubing or you will be out of tune.
2. Attach 3D printed mouthpiece and use a tuner (such as Track Tuner for an iPhone) to verify that it plays a D. If the note is flat, sand off a bit of the end of the tube and if it is sharp pull the mouthpiece out a little (if it is very sharp you'll need a longer tube).
3. Print out a copy of the hole placement drilling guide.
4. Remove the mouthpiece and wrap the drilling guide around the tube. Drill small pilot holes (no more than 1/8") at each of the markings.
5. Reattach the mouthpiece, cover all the holes and blow. You should still get a D.
6. Cover all but the bottom hole with your fingers and blow. You should get a note somewhat flatter than an E as indicated by a tuner. Using the point of a pair of scissors, widen the hole slightly and play. The tuner (and your ears) should indicate the note getting sharper, closer to an E. Keep working the hole with the scissors point until the E is in tune.
7. Cover all but the bottom two holes with your fingers and repeat the process with the second hole from the bottom until you get an F# in tune.
8. Repeat the process for the remaining holes, using the fingering chart as shown above.

Extensions

Can you use other shapes?
Can you make a simple whistle?
Can you make whistles of different sizes?
Can you make a whistle with two tones?
Can you design a new instrument?

Resources

Exploring Whistles
American Whistle Corp
How a Whistle Works

Tinkercad

• The interior cylinder must be 21.7mm in diameter.
• The height of the interior cylinder is 10mm and the offset from the workplane is 15mm.
• The width and depth of the external hexagon is 24.21 x 27.95mm.
• The height of the external hexagon is 25mm.
• The width and depth of the internal hexagon is 15.81 x 18.26mm.
• The height of the internal hexagon is 23 and the offset from the workplane is 2mm.
• The hole in the side (pick a plane aligned with a line of the grid) is 8 x 12, and 2 mm from the workplane
• A wedge 8 across and 8 down is inside the hole
• A slit 8 x 2 is cut from the bottom and must be 2.2mm away from the edge.
• A round roof is rotated and will become the mouth piece. The edge is 13.5mm x 7.40mm. The height is 20mm

Source: ndWaves: Instruments
Air vertebrae in a recorder