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I'll replace these sentences with some explanations of what I did here later. Right now, all I have time to do is upload the pictures (gotta get cleaned up and drive over an hour to a gig venue).

OK...This is a 1960's USA-made (single rotor) bass trombone that had seen a whole bunch of use.
Y'all being a bunch of tuba players, check out the rotor body, and see if you can figure out one of the things that was done today to improve the playing characteristics of this instrument.

Is it a new heavy weight valve cap?

Changed the direction of rotor rotation?

Larger bore Miraphone rotor, that’s been cryogenically frozen twice.

Is there a hollowed-out rotor inside?

Yes. I had altered a single rotor Miraphone bass trombone for this same customer by moving two inline Chinese rotors and their linkage over to the instrument to make it a two valve instrument for them. (They happened to have a Chinese two rotor bass trombone bell section that they got somewhere.) The Miraphone rotor and F attachment ended up being left over.

They also had a single rotor (Elkhart era) Conn bass trombone with a really worn-out rotor, so I transplanted the leftover Miraphone complete rotor assembly to the Conn, and I also transplanted the Miraphone F slide bow to the Conn, because it was such a good match and the Conn F slide bow had been damaged by someone trying to beat the F slide out (obviously, once stuck) sometime in the past.

So the Miraphone ended up being a two rotor instrument for this person, and the leftover Miraphone rotor ended up improving their Conn single rotor bass trombone.

something else:
Both of these instruments were purchased for very low prices by my customer/friend from eBay sellers. The playing slides on both were in pretty bad shape and they are now both excellent. With the Conn, I was able to replace both of the inside slide tubes with factory new ones that fit the Elkhart era outside tubes just fine, and I was able to repair the original outside slide tubes. With the Miraphone, I was able to repair both of the insides slide tubes and factory-new Conn outside slide tubes fit those just fine.

Bass trombone is really not his specialty, but he is the bass trombonist (and a remarkably fine one) in a freeway philharmonic where we both play. Both of these instruments actually sound quite nice, their valves and linkage (as of today) are both good, both have very nice playing slides, and he'll typically bring the Conn to play things like and Schubert and Dvorak and such, and he brings the (now) two rotor Miraphone to play pops concerts and things like that. Thinking of what people typically invest in bass trombones who play professionally, I doubt that he even has $1,000 invested in the pair of these. LOL

also:
No. The geometry of those two rotor bodies did not match differed by about 3/4 of a millimeter), but all I had to do was adjust the positioning of the tighter turn angled tubing branch that comes out of the F slide.

This was pretty major surgery, and I also polished up all the burned lacquer and sprayed over the area again for decent appearance. Everything you see that I did today took about two hours, and that includes a little lunch break.

Not long ago, I refinished both of the bells on both of these instruments for him. I only refinished the bells and not the entire bell sections. It was a barter for him picking up that Conn Orchestra Grand 6/4 B-flat that I bought (which was only about an hour away from where he lives). Had he not gone there in person and paid for it (with cash that he got from cashing a gig check that he had just received) and got it for me, I'll probably wouldn't have been able to get it.

I might have the details confused, but I think I did the two rotor conversion on the Miraphone for him just out of friendship. I was think I was trying to cheer him up right after a deer ran out in front of his car on the way home from one of our orchestra jobs. I think I did that super fast as well, probably also in only a couple of hours. He brought it back later and I redid some things straightened some stuff out a little nicer.

Having hung out in my shop, he has become interested in repair work, has bought some tools, and has actually become pretty good at removing dents. He has smoothed out all of the bodies on his university's brass sousaphones as sort of a donation to the band.

... I don't think he's quite ready to swap out rotor assemblies on trombone bell sections quite yet... Maybe by Christmas.

York-aholic wrote: ↑Sat Oct 12, 2024 6:16 pm Larger bore Miraphone rotor, that’s been cryogenically frozen twice.

Frozen?! Could you, please, let it go.....

matt g wrote: ↑Sat Oct 12, 2024 4:05 pm Changed the direction of rotor rotation?

You know, I've done this as well and on a similar instrument.

In the same orchestra, the principal player has an Elkhart era 88H trombone with the original lever and string linkage. There's something goofy about the way he holds the instrument, and the thrust portion of the lever (where the string attaches) was dragging against his thumb. He was asking me about linkage conversion and all that jazz, and instead of getting all involved in that stuff I just bent the thrust portion of the factory lever over to where it would pass on the opposite side of the rotor stop arm and not drag against his thumb.

Of course, I drilled a couple of new holes and moved the cork plate around to the opposite side, and I had a choice between taking the house top shape off of the rotor stem ("universalizing" it) or moving the stop foot around 90° on the stop arm, and I decided to do the latter. I just cringed when I thought about filing away the house top shape off the factory rotor stem of an Elkhart trombone.

Anyway, the instrument maintained its original appearance and works just like it did before. Most people wouldn't look at it and would never notice that everything had been reversed. Also, I didn't have to buy any parts, and - again - I didn't have to change the look of the instrument away from original/vintage to some modern look (with Minibal links etc).

Strings are a fast yet silent. Just require even more tedious maintenance.

Edit: I didn't scroll down enough and thought there were only 2 replies

PlayTheTuba wrote: ↑Sun Oct 13, 2024 10:46 am Strings are a fast yet silent. Just require even more tedious maintenance.

Edit: I didn't scroll down enough and thought there were only 2 replies

The string is the same one that was on there when he got it from the eBay seller a couple of years ago - and no telling how old it was before that.

It's not frayed, and I went ahead and wrapped the same string around this Miraphone rotor's stop arm.

I view mechanical linkage (for trombones and horns) as unnecessary...maybe even a poor choice.

I got a report back on the 72H and the way it's responding with the replacement rotor. Its owner is doing backflips. I'm glad they're happy.