EDIT 9/1/2021: Iteration #2 is lighter and stiffer as I I turned the parallelogram sides into a triangle. (Last two photos). I dropped about half of the EMT and fittings from the first design.
Say hello to "The Tromboni"! My son and I have been working on this idea since he joined marching band this year. It's an inline trombone rack. He was concerned about traveling with his instrument perpendicular to the bicycle or hanging off the back where the case might flex over bumps.
