This is something I've wanted to do for a while...
Originally, I was going to use a large bore rotary valve set, but upon realizing that I need 15 ft of 3/4" tubing, I opted for a smaller valve set to reduce the weight.
Luckily, I found the Barcone sousaphone that was used for the Bass Horn. The valve set was a little on the small side - .545" - but I didn't have to make a main tuning slide or figure out some of the wrap.
I took the Getzen Baritone Bugle and mounted the rest of my King tubing (after bending them into large crooks) on to the valve section. The leadpipe came from the baritone jazzophone that I had scrapped a while ago for the valve section and modified the first slide into a top slide - it was very successful!
As for the tuba.... well, it's OK. It's about 24 inches tall and has a 10" bell. It plays OK in everything but the lower register - essentially anytime I have more than two valve down, it plays like a bucket, just super stuffy and narrow. It's a practice instrument: practice to see if something like this is possible, which it is, and practice as in something I can practice on if I'm traveling or in a car or bus or if I want to ride a bike somewhere and not lug around a 30+ pound tuba or sousaphone.
About a month ago, I finished the bass horn, but never got around to updating this post.
So, without further ado - the conclusion of the BBb Bass Horn...
I decided not to bend the first valve crook, I didn't think I would have enough tubing left over to finish the fourth valve and have it still play in BBb. Instead, I split a piece of outer tubing down one side and covered the thin spot. It looks a bit odd, but doesn't leak!
Ben was kind enough to stand with the body to show an approximate size for some people that were interested in what I was doing:
I had at first thought of having a removable leadpipe, with a small crook loop, but upon bending it and trying to get it into the right shape AND still be sturdy enough ... I scrapped the idea in favor of a more traditional non-removable leadpipe.
In the next couple of days, in between normal class work - flute padding and trombone slide alignment - I began using what parts I had left from the euphonium to cobble together the rest of the fourth valve wrap and main slide. I used one of the smaller crooks for the second valve:
And fit the inner slides to the crooks (you can see the first slide patch). Before going on to solder all the fourth valve tubing together, I first went over to the main lathe and cut the inner and outer valve slides to the correct lengths - much easier than using the band saw! Each slide has about 4 inches of pull (8 inches total). Though, as I found out, the second slide can only be removed once the first slide has been. The first slide has an ever-so-slight bend that prevents the second slide from being pulled out more than an inch and a half. Of course, the way I play, I don't usually pull out second slide unless first slide is pulled out a bunch.
Sometime the next week or next couple days, I worked on the fourth valve wrap. I used some of the extra inner branches that I bent earlier (I had previously tuned the open bugle). At first, the slide was going to be pulled in the same direction as the main slide, but upon further experimentation, I realigned the tubing so that the slide would be pulled in the same direction as the other valve slides. In the following picture you can see the first attempt at the leadpipe on the left, the first attempt at the fourth wrap, and some approximation of where all the inner branches would be.
I noticed that the inner branches would interfere with the valve caps, so I had to move some of the tubing around so that I could still have access to the rotors for maintenance.
It was a frantic push to the end, as I think I only had a couple days left... Anyway, I began searching for braces and started mounting all the tubing. I bent the leadpipe, fit the slides, tuned the slides, and braced all the parts that needed bracing. I added a thumb hook, though Ben told me I needed a duck foot or some other support that rested on my finger instead of being held by my thumb. Drilled a hole for the only water key - an Amado - though I've discovered that I need at least 2 more to actually drain the water efficiently. I used most of the braces from the euphonium and a few from mini sousaphone. The others were various trumpet braces and some telescoping braces from cornet/trumpet.
I was going to use the Fred Young mouthpiece, but it had just a bit too much of a woofy sound. Fortunately, the Sellmansberger Solo #2 mouthpiece worked wonderfully. I owe this possibly to the fact that the mouthpiece is made to work with F and Eb tubas, but given the french horn length of an F tuba, I though it might work well with a rather cylindrical, almost contrabass trombone sized french horn. It really makes it sound like a french horn in certain registers.
Anyway, here are the final pictures. Since I didn't have enough time to buff all the parts, I decided to go with a scratch brush finish to simulate a satin finish. After playing it a few times over the next couple of days, I knew I couldn't keep the raw brass finish, so I took it over to Kennelly Key's up in Lynnwood and they sprayed a clear coat of lacquer over top. Yes, I know there are still patches of tinning and some heavy spots of solder, but for a PROTOTYPE, it works GREAT... though I still needs to cut the main slide an inch or so....
Hand tuning works just like on a normal french horn, though hand stopping is a little more difficult as the throat is larger than my hand.
As a size comparison, here it is next to the King 2350 and a King 1265 Jumbo sousaphone:
