Every once in a while you get a request to do something outside the box. Ben Anderson, Ossicle Duo and Orchestra Victoria, had one of those requests back in 2017. He was interested in the ability to have 2 different bells on the same horn that would give him more options than his usual bass trombone. 

There were a few influences to the job, one being Rath’s design for Bruce Collings https://youtu.be/JdkcXoQMFUM and Dieter Gaertner’s double bell trumpet for Marco Blaauw https://youtu.be/1Bj8Al9vk4o

The main difference, was he wanted to still be able to use his normal double valve configuration as well as the second bell. This would require 3 valves on a trombone with the appropriate tapers for both horns. From the outset, there were a number of challenges to overcome before construction, and a couple more along the way.

1. TUNING - having enough length on each bell to tune or detune the bells.
2. WEIGHT - placement of the second bell so the weight is managable with mutes inserted
3. STABILITY - maintaining the ergonomics and integrity of the slide receiver without adding significant weight
4. BELL CHANGE - adding a bell change valve without disrupting the taper and having a smooth action between bells

After sending schematics to a number of valve makers we decided on the Meinlschmidt open flow valves for the F and Gb circuits and a custom axial flow from Instrument Innovations for the 2 bells change valve.

One of the problems with the trigger configuration was the bell change valve. I decided to talk to my watch/clock maker friends and borrow an idea of a wheel that would change the angle to a 90 degree action. The wheel was mounted with a bearing to minimise a loss of response from friction.

The other problem I ran into was the trigger layout for all 3 valves. So I decided to borrow the idea from the Schagerl super bone and make the triggers into paddles like this. This enabled the bell change valve trigger to remain in place when the valve and second bell are removed. 

Ben wanted the second bell to be removable so it could be transported more easily and operated as a regular bass trombone. I was able to install a large tapered screw mechanism, similar to one that I had made for Mike Szabo, Melbourne Symphony Orchestra, so he could remove his Gb Hagmann valve independently.

To keep the weight to a minimum I used a web of bracing to give each section strength. There were a number of complex bends to get the Gb section around the bell-change valve and the F section out of the way while keeping the Open Flow valves on the same plane.

I don't anticipate making another Double Bell Bass Trombone anytime soon, but the unique challenges have been useful in subsequent projects. I always value the open-mindedness of musicians like Ben and the value the other local craftsman for their input.