The Great Kurath Re-Tubing

[the elephant]

I have been planning to replace the badly worn, leaking, bent slide tubes in my 1989 Kurath F tuba for years.

When I bought it the entire valve section was on the bugle at a 15º cant because at some time in the past the horn was either dropped onto the valves or it was stepped on. Every brace holding the valves to the bugle was bent sharply to one side. This was so much work that I guess the owner decided to leave it and have the leadpipe adjusted to fit. It played well and I did not even notice this for about three months. But once I saw it I *had* to fix it.

In the process, I decided to also make the leadpipe and valve section removable. It works really well, too. I have been very pleased with this work.

Now I am starting the work needed to replace the gimpy slide tubes. This is not cheap because the horn uses eight different tube sizes, and this gets really costly if you use nickel silver, as you have to buy it in certain minimum lengths.

Additionally, three of the slides need to be adjusted in length. (2nd needs to be trimmed, the two 3rd slides need to be moved higher up, and 5th needs to be doubled from 55 mm of pull to 110 mm!!!) Finally, I plan to reroute most of the 4th slide circuit. Herr Kurath's design provides a supremely open low C, but both slides point downwards, and neither is long enough to be useful. I plan on making 4th have a more traditional wrap with a top and bottom slide.

Today I disassembled the 5th slide from the horn, which was made MUCH EASIER since the valve section is removable.



I dragged my Proxxon mini miter saw to cut the new ferrules, inner and outer legs, and took a minute to match the inner and outer legs and orient them to get the best fit. (Doing this helped me to avoid having to do any lapping after it was all assembled.)

I expanded the crook's ends since the Miraphone tubing was a tiny bit too large for the standard 18/18.5 mm Kurath tubing. Once everything fit I then trimmed off one of the ends of the 5th valve tubes as one protruded into the outer slide tube 12 m while the other was more like 17 mm. One was cut at a fairly sharp angle. Hmm…

Once the two ends on the horn were the same length, level, and dressed I moved to assemble the slide. The original pull length was 55 mm and to be both in tune and CENTERED with a big, fat tone, the 5th slide needed to be pulled out 5 mm more than it had in length, or 60 mm. Again… hmm…

The total length needed from the end of the horn's tubes to the ends of the crook was 12 mm, so I cut inner and outer legs of 90 mm so the slide would be in tune pulled out by about 2 cm.

I reused the Kurath braces, but only out of necessity. They are large circles with long sockets, with thin, fragile, feet and posts, and they are sort of ugly. When I do the rest of the slides I will use the same King (long, diamond-shaped feet) braces I used on my Holton 345. They use a thicker post, socket, and feet, and look much nicer to me.

Those two braces will get replaced when I have more of the King parts. So for now, they are the big discs that I dislike.

The alignment is very decent, and Joe would be happy to know that the slide moves easily enough using LAMP OIL as a lube. However, I will keep using the grease that I prefer.

EDIT: I just noticed that the brace is now blocking the lower 4th piston cap. In reality, you can remove it just fine, but if work has to be done with a reamer or slug you cannot get through from the rear. I detest this sort of bad design work, so I am pissed that I did not catch this. I plan to replace all the round-footed Kurath braces with the much thicker and nicer-looking King braces once I get more of them in the shop, so when I replace that brace I will adjust the position, too.

DANG IT!

Here are some reminder pics of the removable valve section, the old 5th slide, and today's new 5th slide…

Where the slide used to live. (Bb was in tune but horribly out of center because the slide needed to be a good bit longer.)


This is where the slide needed to be.


This is the new slide, which is long enough to pull a lot more, but short enough to push in to close to where it had been before, in case I decide I do not like this change to the horn. After some experimentation with new slide locations for 3rd and 4th, I might decide that this needs to be altered again, but if I like this it is well done enough to keep it for good.


Woo, purdy!


Removable braces — what a great idea!

[the elephant]

I tested the horn for about half an hour, and the low register is MUCH better. Tone, intonation… it is like a new horn in many ways. Nothing was affected negatively. Also, I got to install a pair of my new square-cut O rings on 1st, and that made me happy! HAHAHA!!!

I need a little more of several of the tube sizes, so this project will take me time. I will post each slide as I get to it.

Finally, to Joe: I installed some Allied euphonium springs on this tuba from an old ziplock baggie marked YAMAHA EUPHONIUM. I have no idea where I got these or how the wrong springs ended up in this baggie. However, they were far too weak. If the horn is lying flat on the floor, the valves sag. They do not come back up fast enough. In short: these Allied euph springs blow on a tuba. Once I realized what was wrong (some time ago) I bought a set of *real* Yamaha euph springs. They have worked very well on my Holton, which uses the exact, same piston set (Nirschl-built) as this Kurath. Today another set of these springs *finally* arrived. (Purchased in July and just showing up today. Wonderful.) I installed them and the valves are so much better. Now they are as you describe, and as I have seen with the Holton. They are a much lighter action than the other springs I had been using, but they are still very tuba-like in action. Good call. Thanks!

[LargeTuba]

Does Miraphone sell the cheapest tubing?

[the elephant]

I don't know. I use them for most of my purchases, though. I have had bad luck in trying to order matched sets of inner and outer slide tubing in specific sizes from everywhere but Miraphone.

[bloke]

Maybe you’ve already found this webpage (??), but I think I found a lot of affordable tubing for your Karafe…

https://tinyurl.com/uvkmm26n

serious comment:
I’m sure all the rhetoric to go with your pictures is accurate/precise/well-composed, but I get lost in it. If I’m down there sometime, I’d like you to show it to me in person - and explain everything you did, while pointing to things.

[the elephant]

I made a nice, shiny slide for my F tuba. I plan on replacing all the slides on my F tuba with shiny, new slides. I put the brace in the wrong place but that's okay since I have to replace that brace with a better one after my parts order gets here. The slide I made was longer than the one it replaced because it was way too short. Now the tuba plays better and I am a happy guy.

(Better?)

[York-aholic]

This was so much work that I guess the owner decided to leave it and have the leadpipe adjusted to fit.

[the elephant]

You laugh, but I am absolutely serious. The leadpipe had been adjusted to meet the crooked valve set. It was slick enough that I did not notice this for a few months.

[York-aholic]

I very much believe you. I have seen similar. I guess at times, one needs to take the path of least resistance. I’m glad you came into the picture to correct things.

[the elephant]

Okay, so I have gigged with this tuba a few times since I last posted. The lengthened 5th valve is great, but it is not a panacea for that rotor. I have a better one I will trial later, perhaps this coming summer. I am very pleased with the results, though.

Today I tackled the most involved one, which is 1st on this tuba. It has like a million things soldered to the two outer tubes that can affect alignment as you install each one. As I am (again, and seemingly forever) soldering and such outdoors and it was windy and cool today, I had a heck of a time keeping things the way I wanted them. I had to realign the slide four times, but by chipping away at things I managed to get just about what I wanted. I will go back into this one when I do the much easier 2nd and 3rd slides. These three valves all use the same tubing set, so like with like, I guess. I certainly did not clean up my work properly today. I supposed this is because after all that futzing about in the carport I had reached my saturation point with brass work. In short, I am done for today, and I don't give a rat's posterior where I was when I stopped working. I have to use this horn again on Friday, so I have plenty of time to neaten stuff up. And align the freaking outer tubes. Again.

The slide runs smoothly but is not as loose as I prefer. I also had a great deal of difficulty getting all the schmutz out of the inner tubes. Once all that is blown out (hooray, cheap lamp oil!) it will likely be just fine. But all the heat I had to use to keep the work hot with the cold wind blowing really caused some issues.

I need to build myself a small shop building out back; this situation sucks.

I did not clean stuff up because I will do it all at the end. I just buffed off some of the more egregious flame discoloration and flux gunk (maybe less than five minutes?) and a very mild application of Simichrome so I could see what things look like.

The improvement in this slide is that a previous owner chopped the inner slide legs so that 1st only had like 2.5" of pull, despite having much longer outer tubes. Now the outers and inners match, so I have a much longer pull if I ever need it.

[bloke]

Joe Skillen - recently retired from LSU - plays a tuba very much like yours, is a fine player, and has some really handsome toe-headed sons.
He dropped his off a few years ago for me to do some things to it. I don’t believe it had ever been dropped even once, but the two worst things were the main slide alignment and the really ridiculously bad #1 slide alignment.
I promise I was conscientious (addressing everything that called for improvement), but I just don’t remember much else… It sort of blurs into the thousands (??) of sousaphones that have flown in and out of these doors…
… but there were several other issues.
He seemed quite pleased, when he picked it up, and that pleased me. I’ve owned a rotary one and a piston one. They do require slides that move freely, in my experience… so I’m glad you’ve got that instrument well on its way.

[the elephant]

I think that perhaps Herr Kurath might have tippled a bit when he cranked these early horns out for those "two guys in Michigan". He was not pleased with his deal with them and eventually got out of it. Then this design was "upgraded" (I do not consider the Rotax valve to be much of an upgrade to anything, to be bluntly honest) and he changed the engraving from "KURATH" to "WILLSON" and started selling it as the 3200 FA-5. He seems to have done a better job from that point on. I think he was much happier once his "relationship" with his "importers" had been formally dissolved. (I have those in quotes because I would have chosen different adjectives to describe those two guys.)

[the elephant]

I am awaiting more tubing from Germany from the nice folks at Miraphone. Until then I am measuring, cutting, and getting ready for installation as many of the slide legs as I have tubing for.

With all the different sizes of tubing and all the different lengths of ferrules (thanks a lot, Herr Kurath) I had to make a spreadsheet for a cut list. I am deleting the ones I have finished but the list is still long. Remember that the 5th and 1st slides have been completed and are installed. Tonight I finished cutting and fitting tubing needed for the 2nd and the two 3rd slides that I could make with what I have here. I have five more to go with those two sizes of tube.

Tomorrow I will likely cut the twelve pieces for the two 4th slides from the two tube sizes needed for that circuit.

The main slide is really weird; it is assembled in some strange fashion with the ends sort of layered together. I cannot even guess how I will make those fit the horn until I have fully disassembled everything to see how it all fits together, and how many parts he used. I suspect there is some sort of internal stuff hidden in there that I cannot really plan for. Whatever, once the valve section is re-tubed I might forego the MTS.

No, I won't.

Oh, well…

Here is a pic of the little bit I did today. It took me a looooong time because I need to true up my mini miter saw, and I did not feel like these smaller tubes would look that nice if I used the Dremel. The smaller the tube OD the more fine the fit must be, so the jeweler saw was my tool of choice today, and that thing takes forever to cut all that tubing…

Top, L to R: lower 3rd slide, inside leg, outer tube; both 2nd slide outer tubes, upper 3rd slide inside leg, inner tube; both 2nd slide inner tubes
Bottom, L to R: both 10 mm 2nd slide ferrules; all four 13 mm 3rd slide ferrules

[the elephant]

I have decided to lacquer this tuba or at least the bugle. The metal is so thick that I can fairly beat on it with the buffer, which will allow me to remove some shallow pitting in two places without really hurting the horn. With the valve section removed the bugle ought to be simple to buff, degrease and then spray out in the carport with a plastic sheeting "booth".

If I do not butcher this I might also lacquer the valve section.

If I am feeling very confident after this I might also lacquer the Holton. Who knows? Stranger things *have* happened…

[bloke]

I’m crapping all over your thread, but here goes…

I’m sure you know that the drier the air, the less drying retarder you need to put in your mix, and - thus - the less chance of bugs and dust - as well as way lower chances of blushing and runs.
As friendly advice, I am suggesting that - once one or the other of the tubas is shiny - and you’ve removed dust and rouge powder from the surface (and manually with a very very soft cloth works just fine) - you watch the humidity % predictions.


more: Have some fairly thick (not absurdly thick) mixed lacquer to spray the entire instrument with - which is likely to leave ugly overspray, but way less likely to run. While keeping good track of where are you have sprayed (to avoid spraying too much material on any one surface), have another mix made up (for when you are done) which is probably about 9/10 or 3/4 thinner and a little bit lacquer… I call that “bright coat”. Before the (likely) oversprayed thicker lacquer has dried…and it dries quickly… hit the entire instrument (moving FAST and LIGHT) with that “bright coat” - to get rid of overspray. It’s just (almost) too damn hard to lacquer an entire tuba without overspray, because there is so much surface area and so many angles. That’s why I recommend hitting the entire instrument with “bright coat” after you are sure you’ve covered everything.
OK… I can’t stop typing… Bell interiors are treacherous. remove dust and etc. from way way down inside the bell ahead of time. Maybe, stuff a slightly oily towel way down in the bottom bow, to keep the air - from the lacquer gun - from bringing dust up out of the tuba body onto the interior surface of the bell flair (which can be heartbreaking). Go pretty easy on the bell interior with a regular mix of lacquer (that is more like what you would mix for spraying a trombone or trumpet). Try to cover the whole bell interior with no overspray - absolutely as quickly as you can - and STOP.
===========
Wade probably knows all of this stuff, but I’ve done a bunch of hillbilly outdoor tuba lacquering jobs, and I’m just trying to offer advice from my experiences to whoever is eavesdropping, and might be considering doing it themselves as well.

[the elephant]

All good points. I learned to do full-on lacquer jobs to tubas in a very slick downdraft booth while wearing a Tyvek suit with booties and hood, a respirator and face shield, and (like you, due to the humidity) about four mixtures, one set up in each of the four guns, for whatever might happen in the booth. It was great (and quite easy) to lacquer under such circumstances and I was quite good at it.

However, I have not done this specific work since about 2003, and I have *never* had to do it outdoors. However (I seem to like that word tonight), I have painted cars outside in my carport and had great success. I was hoping that with a little bit more prep (making a "booth" to keep contaminates out of the workspace, etc.) that spraying a tuba would not be all that traumatic for me. However (there it is again), I have little hope for things to work out so well as my paint jobs on our cars.

I appreciate the reminders about humidity. It generally stays about 85% here most of the year, so the white blooms are almost unavoidable. I use the flame to work them out and it looks fine, but it is always sketchy if I have laid down too much lacquer/retarder on the surface and it is thick and slow to dry. (Many years ago, I set a freshly lacquered trombone hand slide aflame by trying to remove the blooming using my acetylene torch. I learned to use a cigarette lighter from that experience. It works more slowly, but I have never had the wet lacquer burst into flames as that one epic trombone slide did on me. That was a bad day!)

I really hate doing this stuff, not because I am weak at it, but because, even with a full-on respirator with the double filter boxes hanging off the front I wheeze for many hours afterward. My asthma or allergies hate the retarder that we have to use down here in "God's Own Sweat Box".

When (if) I get up the gumption to do this I will probably call you, as in an actual "ringy-dingy" ($1 to Lily Tomlin) so you can grill me with the procedure before I go and F up my horn.

[bloke]

Yeah… It’s not something that I brag about, nor consider particularly competent at doing.

If you have a still day in the winter – such as it is (mostly mildish) in Yazoo City – with maybe only 60% or 55% humidity…?? - that might be “the magic day“.

It’s your decision, but you might just forgo the makeshift booth. Maybe the bugs will be dead, maybe there won’t be any wind and there won’t be any dust, and maybe putting up a booth might (??) just offer four nearby surfaces from which dust might be blown right on to the instrument.
No…of course, I never do this in front of anyone, but about all I wear – when I lacquer - is a pair of satin-ish sleep shorts with no shirt and no shoes. Most other clothing has fuzz on it… and I usually wet my hair down, just a little bit.

[the elephant]

I had to pawn my spray rig, so I only have rattle-can Nikolas, and it is an unused can but has been on the shelf for years. I had thought to do just the bugle with this stuff, but it always seems to get "fragile" after a few years and I do not want to do this a second time.

However, it *is* tempting. The bugle on this horn is a single loop, very open and simple. The weather is just right.

I would have to shake the sh¡t out of that can for hours to get it mixed up well enough, but the temps and humidity are going to start sucking soon. I have a nice buffing setup, if somewhat small, and I just got a new brick of red rouge.

Tempting…

[bloke]

It doesn’t take all that many SCFM’s to put out a nice pattern, and harbor freight sprayers really aren’t all that bad.
I believe someone near you would probably loan you a 110V compressor that could do the job, and - if you didn’t want to buy a harbor freight sprayer - I could mail you my old Binks, if you would mail it right back, when you’re done…
… or just bring the shined-up tuba up here, and spray it right out the barn door. If it picks up a couple of smudges in your car, you could touch them up on my buffing machine.

[the elephant]

I have one of those 15 gallon Dewalt compressors, but it is single stage. It worked to paint the two cars, but it was sketchy.

I will be getting a Harbor Freight rig when the time is ripe. Or, if I am lucky, something nice (and appropriate for lacquer) will show up on Craigslist when I actually have cash on hand.