On the question of bell ripples

Many makers believe that bell ripples are unavoidable considering the large diameters and the volume of bending medium required to fill the bell. The traditional approach to bell bending allows bell ripples to form and then uses various processes to remove them such as hammering, burnishing, and filing. Contrarily, I believe that bell ripples are undesirable and avoidable. Bell ripples are an indication that the maker has pushed the brass past the point at which the material is flowing (compressing or stretching), and into over strain and buckling.

There are some serious implications for bells going through a process which allows it to ripple.

First, the strain in each peak and valley is much higher than the material around it. The force required to remove ripples is more than you might think and the force applied to a ripple doesn’t always flatten the ripple, it often sinks the entire ripple further into the bell. Makers often will use the bending medium under the brass to flatten ripples, rather than a forming mandrel, so the brass ends up taking the shape of the deformed bending medium rather than the original mandrel it was produced on. Once the bell has been rippled, it will never again take on the shape of the mandrel that made it. Straight bell tails are produced by drawing and spinning and its a one shot deal. Flattening ripples, even using steel mandrels can only approximate the original bell. Its as if you are doing a bell tail repair before the horn has even been made!

Another problem is that the surface of the bell tail is not uniform or smooth after taking out ripples on a tail. There are large hammer and burnisher marks and there are also usually places where the ripples have buckled inwards rather than raising a hump. Those inward buckles can’t be hammered out so the traditional technique is to file the surface smooth to remove the appearance of buckling. When you resort to filing and sanding lumps and divots in the brass surface, you remove more material, and in a less consistent way that normal finishing procedures.

No no no no.

Most of the time, the player won’t ever know (or maybe even care) about the shape of the bell because its extremely difficult to see and even harder to measure once the surrounding parts are installed. However, bell tails play a very important role in the overall intonation of the horn. Having variations and an inconsistent taper inside the bell tail can cause intonation quirks that are undesirable. Additionally, the bell tail is the final part which transfers vibration and resonance energy to the bell tail. Inconsistent material thickness and hardness can affect how much energy and how cleanly it’s passed on to the flare.

Bell tail ripples cause major problems in a critical part of the horn that can have serious implications to playing in tune and having a clean playing experience. Being trained in traditional horn craft, I am well aware of the presence and reasons behind the ripples, but as I have explored ways to update traditional techniques, I have come to the conclusion that there is a better way.

Bell ripples are an indication that the maker has pushed the brass past the point at which the material is flowing (compressing or stretching), and into over strain and buckling. This can be caused by a number of factors from incorrect annealing procedures, to poor jig designs, to a lack of understanding about how the material moves as the bell is bent. Bending a bell properly is a delicate dance with many pitfall and variables to keep track of, but when done right is an excellent start to a great horn.

Fresh off of a fully supported, 2 step bending jig and not a ripple or blemish in sight.

The bell is surprisingly important in sound transmission and intonation, excellence with these techniques pays large dividends.