above: the typical split linkage
Here is a useful trick that I stole from my friend Michael Riepe. Some models of Miraphone/Mirafone Tubas have linkage arms that connect to the lever and stop arm via these gray or white ball sockets. They seem to break regularly, and they aren't cheap to replace. You can modify the horn to take uniball linkages, but that isn't cheap either, so we have figured out a way to fix them.
This is really easy. All you need is a Fox L15 water tube for a bassoon. You cut the water tube to length so that it just covers the cylindrical shank of the linkage. It is a very tight fit, and you will probably need a plastic mallet to gently tap it on.
Here is a picture of the water tube cut to length:
Here is the final repair all assembled:
NOTE: When tightening down the plastic set screw in the end of the "bulb" be careful not to overtighten it as this will split the bulb.
What do you think?