Miraphone 4V to 5V conversion
Well.... the first thing to do is select a Miraphone 186 from 'the herd'. In this case, I decided to use a horn that was rescued from a school junk pile a few months back. This horn has already received substantial time in the shop to repair valve body crushed tubes, damaged rotors, a crumpled bell, and a severely dented bottom bow. I replaced the bell with one that is a great match for the original bell except that it does not have the garland. When trimmed to the prescribed length, the throat of the new bell mates perfectly to the Miraphone stack ferrule. At over $1,000 a pop for a new Miraphone bell, I can live without the garland. I've been experimenting with replacement bells for the 186's for a while and the performance of the ones I use, in my opinion, is BETTER that the original bells. Anyway.... getting started, the first thing to do is remove the leadpipe. This one component that you don't want to mess up as new ones are well over $200 just for the pipe. I like to used old business cards to slide between the horn and the leadpipe as areas are unsoldered.
Parts is parts! A project like this cannot be started without an ample supply of bits and pieces that match the bore of the horn. In this case, the parts came from another Miraphone. The 'donor' horn had already been used for spare parts before I acquired it. Luckily, there was one good rotor assembly and this mess of tubes, crooks, and slide tubes. One of the time-consuming aspects of a project such as this is making sure all the parts are stripped of lacquer, clean, free of dents, and have all the old solder removed before beginning.
The picture on the left shows the 5th rotor and the tubing on the front of the horn. The picture on the right shows the backside of the 5th rotor wrap coming through from the front side. Everything is hand fit before soldering anything. The slide assembly on the backside was changed later to a slide that is about 1 1/2" longer. My starting length for the 5th valve circuit was about 56". I have found that it's a lot easier to start with tubing longer than is required and trim it down later to 'tune it in'. After I had everything hand fit, I took it all apart and soldered one joint at a time and leak tested the joints as I went along. The transition from the rotor to the back side was a very close fit! You can see that the 4th rotor tuning slide is very close! Closer counts!
Crafting a linkage is always a challenge! This one worked out very easily. I used an 'S' link from the 'donor' horn and fixed it rigidly (with a piece of #4-40 all thread rod) to a piece of 3/16 solid rod about 4 1/2" long. On the end of the rod is a finger button. The rod runs inside of a piece of tubing that fits the 3/16" rod very well. The tubing is attached to one of the #1 rotor tubes with and standoff from my 'hellbox' A washer is soldered to the outside tube to serve as a spring stop. With the addition of a light compression spring, the mechanism is complete. Things need to be cleaned up a little and buffed... but you get the idea. I'll probably add a sleeve to cover the exposed spring later. I'm thinking about NOT putting a thumb ring on this horn. I usually play my rotary horns with my thumb hooked under the #2 slide, anyway. I've never seen a thumb trigger/thumb ring combination that was comfortable for me. I may come up with a device to actually work like a strap over the back of my wrist for this application.
I've replaced the button and spring mechanism with some saxophone (ugh) parts. Scroll to the end of this page to see the generation two mechanism.
In the pictures above, you can see a side-by-side comparison of the 4V to 5V conversion. The 5V is on top and the 4V is on bottom. (of course, you probably already had THAT figured out!) Note that the leadpipe is about 3" lower on the 5V. This is a matter of my own preference. I like to play with my horn in my lap instead of on the edge of a chair or on a stand. In order to do this... while the leadpipe was off the horn... it was annealed (heated to red-hot and air-cooled) and filled with pitch. If these two things aren't done prior to re-bending the leadpipe, it will kink and/or crack. Annealing is usually done to a horn several times during the manufacturing process so the brass can be formed. Brass work-hardens whenever it is stressed and will crack unless annealed. Once the re-bending is done, the leadpipe is heated and the pitch runs out. The pitch can be used over and over. A little further heating will turn any remaining pitch to ash and it can be simply washed out. Another note is that the old leadpipe had to be shortened at the large end an amount equal to the distance that the new rotor occupies. Note that the 5th rotor wrap on the front side of the horn is also shorter that in one of the previous pictures. It was left long for tuning purposes. Once trimmed to the correct length... with the tuning slide out about 1", the 5th rotor produces a 'right on' C sharp and F sharp. Yep! I learned a lot on this project! I don't care how many horns I fix, there is something to be learned from every one of them!
Yep! That's a key off a bari sax riding on a roller pin that is screwed into an altered Miraphone paddle bar mount. A tab was silver-soldered to the sax key for the DuBro ball to mount to. I also decided to put a finger ring on this horn. The location of the finger ring barely clears the removal of the 2nd rotor slide. Played it at community band rehearsal tonight. Works just fine!