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A friend - who plays a Conn 72H bass trombone quite a bit (more of a tenor player, and also an alto trombone player) ALSO picked up a semi-unicorn 1970's Miraphone (yup, made right there in Waldkraiburg, Germany) bass trombone which is a COPY of a Conn 72H.

They own NO two-rotor bass trombone, but have a Jinbao (Yamaha-like) two-rotor bell section.

They've asked me to do a transplant of the two-rotor system onto their Miraphone bell section (to avoid "funking up" their Conn).

I've budgeted two hours for this gig...
...so how long do you think it will take me?

If/when this happens, ' y'all want pictures, or not?

I found this clip from a Tchaik 4 rehearsal of him playing the Miraphone bass:
https://www.facebook.com/eduarbone/vide ... 6575063648
I wasn't there that week (admittedly: prostituting myself out to play fourteen notes for mo' money), called Todd French (an extraordinary player) to sub, and - happily - he was available.

Here's a picture of it - right after I first got it "workin' ".
Yes...The rotary valve cap has the flowery engraving on it.
(Later, I replaced the outside slide tubes (with Conn tubes).

Two hours!? Pictures, please.

UncleBeer wrote: ↑Thu Dec 29, 2022 7:05 pm Two hours!? Pictures, please.

...so you think that includes too much screwin'-around time, or what...??

That’s one industrial trombone stand!

I know Todd French! I took lessons with him my senior year of high school! He's out in your neck of the woods now huh? Cool beans. He was here getting his masters I believe.

Tubajug wrote: ↑Thu Dec 29, 2022 8:11 pm I know Todd French! I took lessons with him my senior year of high school! He's out in your neck of the woods now huh? Cool beans. He was here getting his masters I believe.

Assuming good weather/traffic/etc., he lives/works less than two hours north of that particular venue.

bloke wrote: ↑Thu Dec 29, 2022 7:09 pm

UncleBeer wrote: ↑Thu Dec 29, 2022 7:05 pm Two hours!? Pictures, please.

...so you think that includes too much screwin'-around time, or what...??

Noooo. That seems crazy quick to me. I doff my chapeau in your general direction, sir.

Adding a single valve to the Miraphone would be a really big job of rewrapping the F side, rejiggering all the braces and swapping a lever over.

Making a plugin valve would take time to rewrap the plug, but to me is the best way to get a double when you have a single (without destroying the single).

If you take out the single valve, cut the neck pipe, and stuff in the double set + wraps, it should take minimal time. Adjusting the braces will be the big job.

You could avoid most of that work by taking the bell and slide receiver off the Miraphone, and putting those back on the JB bell section. You could probably do that in 30 minutes. And good news, the JB will probably also have some floral pattern on the valve caps, yippee

I know only one guy who owns a converted 72h. Most people just buy another horn when presented with the cost of making the swap, especially if they want good valves.

Transplanting the Jinbao section onto the Miraphone section seems reasonable in short order if the parts line up pretty well.

Big “if” there.

LOL...

Thanks for all the advice.

I'll have the guy who owns the 72H time the job, and stick up a few pictures of the after.
(' y'all want "before" too?)

Someone (is there a plural of that?) may be imagining an over-complicated version of the job.

The Jinbao bell (with the two rotor system on it) sounds like a lot of Jinbao bells - compared to what they're supposed to replicate.
(Previously, I stuck a JP/Rath slide receiver on it, so the owner of it could use it with his JP/Rath slide...but - though he still owns the JP/Rath single-rotor bass - they've moved on to the Conn and Miraphone.

The Miraphone bell - in some ways (to my sitting-next-to-it ears) sounds just a bit better than the 72H bell.

This is not any sort of "precision-fit" (as far as a single/double cluster being able to hang off a bell section).
Based on all the gimmick-valve conversions I've seen, "techs" goof up mounting jobs as badly as 1/4" and - somehow - still seem to be able to make them work.

bloke wrote: ↑Fri Dec 30, 2022 10:21 am Someone (is there a plural of that?) may be imagining an over-complicated version of the job.

I allow a whole lot of 'head-scratching' time when doing mod work.

This is probably going to be about like taking off a muffler and replacing it with another muffler plus a resonator...

... and - of course - I'll have to install a couple of new "hangers".

Even the most different bass trombones - unlike tubas - only vary a little bit as to their general dimensions...

...OK...with the exception of some never particularly popular long mothballed models made by shuttered factories.

Whenever I stick gadgety aftermarket valve assemblies on trombones, the portion of the job that takes the most time is ordering all of the crap that the person wants. I make more money per hour when I put the responsibility of ordering - all of the crap that they want installed - on the customer. Thankfully, the manufacturers and resellers of that junk have made it pretty easy for laymen to order the parts.

IF;

You already know what you are going to do,

You have done it several times before,

You have all the parts and supplies handy.

I voted 1.5 hours but I'd bill for two just in case.

What do I win?

I think there's a pretty good chance of you winning, particularly if shoe-shining and rattle canning around the solder joints isn't included in the time.

I voted Umbriago, because I figured very few people would know anything about that unless they used a search engine.
I knew about it, fwiw, when I was 2-years-old - which is about when I learned how to use a record player/changer. Let's just say I was a fan of being nosy.

The owner of this instrument follows this website.
I wonder if they'll comment on how many minutes it took me to swap out the outside slide tubes on this instrument, and - several years earlier - how long it took me to take a former colleague's (now: trombone professor at U of Northern Iowa) Edwards playing slide apart, straighten all the tubes, and put it back together. (That person was actually on their way to an orchestra rehearsal.)

The one with the Conn balancer stuck on it is actually a Miraphone knock-off (notice fancy engraving on rotor cap) of a Conn.

The other is a Jinbao with a JP/Rath slide receiver stuck on it.

' roughly a dozen solder joints to undo (heat-pop/heat-pop/heat-pop/heat-pop/heat-pop/heat-pop/heat-pop/heat-pop/heat-pop/heat-pop/heat-pop/heat-pop)...

a gooseneck to (possibly?) trim down and re-taper

' roughly six solder joints to put back (possibly, two or three more - if one bell section is significantly wider than the other) and clean-up/shine-up/hit with the rattle can

I guess (??) I could manage to make this take more than two hours.

After all, some of the stuff that I should do (that I don't want to do) has - so far - taken years.

The single poll participant who guessed 3 hours was correct.

It took some time to make a super-short gooseneck (yeah: "bloke the artisan" ) that is only about 1-1/2" long yet the o.d. tapers from .605" to .675".

Also, there were some Jinbao-issues (never-soldered joints on the two-rotor assembly, Jinbao rotor action, etc...)

...so it's stuck together.

Next time they're here, we'll pretty it up some...but it wiggles and toots.

1970's MIRAPHONE-MADE COPY of a Conn model 72H bass trombone with a JINBAO 2-rotor system transplant:



Anyway, he now has his nice old Conn 72H and this whatever you want to call it double rotor bass as well - and without having spent $6000, $7,000, or whatever.

There are still several upgrades that he could do to both of those bass trombones, but I think he's planning on trying to hold on to his money and get things done a little at a time.

There is still clean-up and dejinbaoization of rotors left to do (for next time), but I let the owner take it home and play with it.

They are tickled with the low B-natural.

https://i.imgur.com/OuX1a1t.mp4

The day I did that work, my friend had to scoot, so the conversion was crazy-hectic.
Additionally, I found (on that day) that I was going to have to make a crazy-short tapered gooseneck tube (in order for it to work).

When his wife and children went to visit her relatives in another state (a couple of days ago) - with him staying home to look after all the pets (many), he slipped up here again, and we spent yet another hour and a half (??) lining up the rotors' circuits more nicely with the bell section (ie. colinear with the bell section - as well as coplanar with each other.

Being that the circuit widths are narrow (compared to many other bass trombones) and thus LONG, finding places to brace everything (particularly with him being unwilling to surrender the main slide's cross-brace) is a challenge. I found some places to brace it up, but - with this extraordinary amount of overhang - it's still a bit flexible.

There's ONE more place that I can brace up one of the two circuits, but he had to head back home (dog/cats/etc.) so I'll do that one next time. (It involves a curved and ground-down piece of brass rod brazed to a flange.)

I could brace across each pair of tubes, but I'm thinking that will just add additional weight, and won't do much to stiffen anything up.
I suppose I could use some of those threaded/removable braces, but whatever. It will be just fine...and (with what he paid for this formerly-quite-distressed 1970's Mirafone knock-off of a Conn 72H (as there really weren't any American style trombones made in continental Europe at that time - yet they were quite popular) and what he paid for the Jimbo inline two-rotor bell section (and yeah, I charged him for a couple of new genuine Conn outside playing slide tubes) this instrument (which sounds quite good) was comically inexpensive.

Anyway...The two rotor circuits are now much more nicely-aligned with the bell section.
Someday, we might even clean up all the solder joints much more nicely, polish it up, and put a finish on it...(??)

sound...??
This Mirafone thing's resonance is very much in the vintage Conn "family", but with a little bit more "teeth".
He also managed to pick up a vintage (Elkhart) Conn (ie. real) 72H. It sounds "prettier", but he has to work harder to cut through (ie. keep up with bloke ) The Conn 72H was also crazy cheap, but I believe I remember that I had to replace all four playing slide tubes on that thing. (Rightfully so, he didn't want to mess that Elkhart Conn single-rotor bass up with budget Chinese valves, and is keeping it as an oem traditional-wrap single-rotor bass. (Years ago - when he began playing 3rd with this orchestra - he didn't even own a bass. Now, he's quite the competent/pleasure-to-work-with bass trombonist, and - differing from lesser players - hasn't dumped $6K - $8K into some super-boutique gimmick-bass.)

work shortcuts, to speed things up...??
You bet your life...such as heating BOTH ends of that short dogleg, and rotating it to the needed angle WITHOUT removing it and reinstalling it.
...and all sorts of other similar shortcuts.

...the letters...??
He stuck those on there (I suspect) to poke fun of me - poking fun of myself.
When I did the supplemental work (a couple of days ago) I measured across the main slide inside slide tubes.
Congrats due to him, he did NOT f-up the main slide's alignment when soldering on those letters.

bloke " 'We' don't work on that brand, because it's too hard to get parts."