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I was thinking about an Eb sousa for the range flexibility, and I've seen the thumb-actuated rotor added to horns before.
For those of you that have them, how well does it work?
For those that do the modification, is it a giant pain in the rear or relatively simple? Could you add it to either side of the MTS or just after the valve body?

Hey! I didn’t find it to be too much of a pain doing it on my personal horn. I added my fourth valve right after the valve casings. Mine is actually left hand actuated I did this mainly because that what I’m most used to! Feel free email me if you have questions! p(dot)chadbourneii at gmail (dot) com





I decided to get a little fancy with one of the braces supporting the tubing for the fourth valve

As an add-on 4th valve I think a rotary is easier to do than a piston because the in- and out- ports are co-linear.
I put mine on the larger-bore side of the main tuning slide because that matched the valve bore and because I wanted less resistance in the 4th valve tubing, but on an Eb sousaphone I think resistance will be less of an issue. Put it wherever the valve bore matches the tubing. Rigging up the linkage is an enjoyable opportunity for creativity. The ideal place for the paddle pivot is beside the first knuckle of your pinky, so the paddle follows approximately the same arc as your fingertip.

http://www.galvanizedjazz.com/tuba/frugalhorn.html

Adding a 4th piston valve, done correctly, is not an easy procedure. As Art said, lining up the ports is difficult, but simply finding a suitable valve can present issues, too (think about finding a valve to add to a 3 valve Holton .750 set....) Obtaining a rotary valve of the correct bore is considerably easier, IMHO.

Throw in the skill aspect (such as silver-soldering, and making and mounting a perfectly contoured sleeve to make it "look right"), and you've got even more difficulties.

Then, the 4th valve circuit needs to be "tubed", and due to its length, can be tricky just to find logical places to put it.

The Tuba Tinker made a very informative page on his website to describe all this:

http://thevillagetinker.com/yamaha_yeb3 ... ersion.htm" target="_blank