<aside> 🚧 See my progress docs here:
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Goal: Make a bell & get a clean sound on 1 note
<aside> 💡 A note on dimensions: soprano trombones are not commonly made or used, so their dimensions are hard to come by. The best I could find are listed below, but most with only one or two sources (not much evidence). I made some assumptions about implied dimensions from scaling down from a starter tenor (larger) trombone CAD model, with the main ‘driving’ dimensions being the 5 in. diameter bell, and the 0.470 in. inner diameter straight tubing
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Updated MVP straight bugle (mouthpiece + 9” tube + bell). The bell dimensions match my plan for the eventual trombone, as well as the straight tube length, which is the length of tubing that will attach to the bell, be bent, and continue on until it meets the slide tubing! It didn’t make sense to make a super long bugle to match the actual trombone pitch, so I figured I would get comfortable with some of the dimensions of the eventual trombone so it is also easier to iterate on.
From my extensive research on how trombones & trumpets are made, as well as consultation with many expert fabricators at Tufts, I have devised a plan to make two mandrels to help form my bell: a bell mandrel (for the flared, lower ~4.2 in. of the bell), and a tube mandrel (for the ~8 in. cone-like tube that transitions to the flare).
The bell mandrel will consist of 1 in. stacked disks of oak, a hardwood that will hopefully hold up to hammering 24-gauge sheet brass against it, which I will cut out as circles to start, then CNC the side curved profiles, stabilize & align the disks to be centered with a 3/4” dowel down the center, and glue the disks together. I’ll probably sand the wood down to make sure it’s nice and smooth before pounding metal against it.
That weird cylinder/cube extender below the bell is a placeholder for some sort of extension of the mandrel so it can be easily & tightly held in something like a vice grip while I hammer the metal against the mandrel.
Mandrels
Bell over mandrels
Raw material sizes to make mandrels
I laid out the stacked raw circle drawings in OnShape to get a rough idea of how much 1” thick sheet I’ll need — the image is scaled down by half, so I need about 16”x6” of 1” thick sheet (assuming all goes well 🙂 — I’ll probably try to cut some samples out with the CNC with scrap wood at Nolop/Bray first to make sure the CNC cuts my file the way I intended). Units in inches below.
