Posted by Rick Denney on June 19, 2002 at 13:08:19:
In Reply to: Eb modifications=CC posted by Dr. Phil Golson on June 19, 2002 at 11:31:22:
A tuba comprises several basic elements: A bell stack, bottom bow, top bow, inner bottom bow, inner top bow, dog-leg, tuning slide, maybe another dog-leg, valve body, and leadpipe. You'll have to add about three feet to convert an Eb into a C (measure the length of the third valve on your Eb for a closer approximation), which I would expect entails adding another inner bottom and top bow and making adjustments to the tuning slide. You find something that's close, and then work it into the right size. You'll probably end up retapering existing bows, too.
The result will probably be no better than my project tuba, which means it won't play in tune or it will have holes in its scale. Beware!
A more typical approach is to take a BBb body with a tuning slide in the leadpipe and a tallish bell, and replace the bell with a short bell from an Eb Monster Bass and a straight-in leadpipe. The pros will replace the entire valve body up through the tuning slide and fabricate a new dog-leg to mate it to the bugle. Matt Walters created a beauty with a Buescher BBb bell, a Nirschl bottom bow and outer branches, and, as I recall, a Meinl-Weston valve body. Don't expect results like that from a project--you don't know how many horns Matt converted getting to the point where he could do that, and he didn't even start until he was a highly qualified repair technician.
The more parts you have to choose from, and the more experience you have, the more likely your results will be acceptable. The Conn 56J was prototyped in this fashion. Sam Gagney has also made several like this with good success. They basically use the valves and bottom bow from a King BBb tuba, plus the bell from an Eb tuba.
The time required to do this is enormous. I'd guess 100 hours for the conversion, plus the time require to overhaul the parts. If you just want the result, call Sam and look at the ones he has already converted and that he occasionally offers for sale, or look into a Conn 56J.
I learned this from my own project: This is not for hobbyists unless abject failure is acceptable and even expected. A desire for the product is a rationalization, not a motivation. For example, John Swenson offered to craft a valve extension for me. I told him it was too much to ask. He replied that he already had the lathe and he NEEDED a project. That is the only acceptable motivation for a hobbyist taking on a conversion project. If you don't understand that perspective, then run away. The biggest project I'm likely to attempt in the future is converting a top-action BBb tuna into a front-action BBb tuba, which doesn't require retapering anything.
Rick "who succombs to the occasional fit" Denney