Adding a 4th valve

[Bbfoghorn]

Hello all the Frankentuba builders out there! I pose a question. On a BBb 3v top loader tuba, conventional or compensating, I would like to add a rotary 4th valve downstream of the valve block. Do I understand correctly that it does not have to go back through the valve block, only if you want it to be part of the compensating loop? I'm investigating adding a thumb actuated rotor for 4th instead of 5th. the thumb works much better than the pinkie. On Eb it can be a step to the larger tubing just before or after the bugle. Same for a smaller Bb. In a larger BBb a rotor seems to open up the bottom better than a piston for some reason. Does this hold true with non-comp horns also? Foggy

[Bbfoghorn]

A quick Edit, I meant just before or just after the main tuning slide, not the bugle. Foggy

[iiipopes]

I thought about this years ago as a way of extending the lower range of my Besson New Standard 17-inch bell BBb 3-valve comp, since privilege tones were essentially non-existant on it. Because you have to be careful of the bore expansion and find room to plumb it, if you are going to do it, put the 4th valve before the main tuning slide if you are wanting a conventional 4th valve. Another option is to make it dependent in the 3rd valve circuit if all you are wanting to do is get low Eb or get 1+2+3 valve combination notes in tune, as on some Yamaha euphoniums. But frankly, there are inexpensive 4-valve conventional tubas out there, and you are better off purchasing a 4-valve, as I did, instead of trying to add a valve. It's like trying to hot-rod an old car: the more you do, the more that will have to be done. You may have to move braces, you may have to adjust the rest of the tubing depending on where you put it and how much is cut out to plumb the 4th valve (for example, on a lot of 3-valve tubas, the 3rd valve circuit is long for 1+3, which you don't need, although it is convenient depending on certain passages, if you have a 4th valve), designing the linkage to make it easy to get to, etc. Great idea, didn't work for me. Even Blaikley on his original 3-valve comp patent had an alternative to mount a valve to get 1+2+3 in tune, but in practice didn't use it because of the added complexity, and on a comp tuba you really don't need to lip low B nat and E nat as much as you do on a non-comp tuba. Projects such as these are similar to the fad a generation or so ago, led by Bob Rusk, cutting a BBb tuba to CC, when there was a much smaller selection of quality CC tubas. Now, nobody really talks about it much, except to repair one.