Popular Mechanics Dec 1982 construction article for a 25 note mini-calliope.

Calliope Tuning Plugs for 1", 7/8", 3/4" and 5/8" OD 1/16" wall aluminum pipe

Tips are gladly accepted and much appreciated.

Mini-Calliope Part 6 - Pipe Tuning Plugs & Jacks
https://youtu.be/4U84IxTTqpM

Mini-Calliope Part 12 - Pipe Tuning Process
https://youtu.be/oiF2LTt6MI8

The 1” and 7/8” plugs are threaded for 5/16-18 threaded rod.

The 3/4” and 5/8” plugs are threaded for 1/4-20 threaded rod.

Note: Print plugs with threaded end pointing down

Required o-rings listed below and are noted in the stl description for each tuning plug.

1” Tuning Plug uses 1.5mm x 19mm O-rings

7/8” Tuning Plug uses 1.5mm x 15mm O-rings

3/4” Tuning Plug uses 2mm x 12mm O-rings

5/8” Tuning Plug uses 0.375 x 0.5 O-rings

Creality

Ender 3

No

No

0.1mm

40% to 80% depending on plug size