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Just yet another "show and tell" project.
I was finding that on my F tuba both the 5 and 6th partials are about 15 cents low.
The 3rd partial (C) is conversely a tad sharp as are the fingered notes stemming from it.

Earlier attempts at intonation correction resulted in venting the valves and pulling a pushing slides 1,3 & 4. Not so much an issue on long notes, but a real pain when in quicker passages.

Two friends came to the rescue. Bill Milashius, a former student and now successful machinist, designed and built a double direction piston with a turnbuckle tuning mechanism.
Eric Peterson, a very well respected technician in the Minneapolis area, and BTW an excellent tubaist, did the preparation, installation and fabrication of braces.

The concept is quite simple. The double spring piston allows for about a 1 1/2 inch pull or push, with an automatic return to the orginal position. The general tuning is set by the turnbuckle that has reverse threads on one end to allow the rod going to the main slide to be increase in length.

The BMB F tuba has had another issue with the thumb ring and tension elastic band for the rotor return. The bar that previously held the thumb ring and the nub for the elastic band were removed. The original ring was re-installed onto the tuning piston by way of a hand made brace and a new nub, now with a more substantial O-ring, is permanently soldered to the piston. The piston is attached to the slides coming out of the 5th valve rotor.

The rod is controlled with a black ball on the top end of the rod which is very comfortably positionsed for an effortless pull or push.

The two photos were taken while the apparatus is still in the prototype stage. We have the option to make some changes and then it will be removed and sent for silver plating and then permantly attached.

Incidentally Eric had to work rather hard to line up the tuning slide legs, as is in most cases, they were not perfectly parallel. They now move like a trombone with next to no binding.

Now it is so much easier to get some of those stuborn notes in tune without having to distort the face muscles. I find that it really minimizes fatigue caused from having to do so much lipping.

Now it just involves the coordination of when to pull or push or just leave it alone.

Paul (a happy camper) Maybery

Oooohhhhh! Very nice, and very clean work!

My tuba is going up to him very soon as well, but just for repairs. Good to know he can do this quality of work though!

It's hard to tell, but the black loop off of the top branch is for the left hand (wrist).
That picks up the lateral weight of the tuba (which it tilting to the left) and puts the LH in position to work the knob.
It is extremely comfortable and is made from an inexpensive saxphone neck strap and some velcro. I used it long before I added the tuner gizmo. The tuba is very comfortable to hold and sits nicely on the inner part of the right thigh. Part of the BMB design was the addition of a crossbar on the back to rest the left arm when adjusting slides. I wound up covering it with a leather wrap from Sports Authority.
I appreciate where it is located very much as it keeps the left arm relatively low and makes for easier breathing and a less tired left arm that would otherwise need to reach over the top or around to the left side. Extremely ergonomic.
The next tweaking will involve building a thumb lever to operate the 5th valve rotor.

The self centering piston bit appears to be part of the first valve gadget from an old Reynolds tuba.

bloke wrote:

cjk wrote:The self centering piston bit appears to be part of the first valve gadget from an old Reynolds tuba.

yup.

I have two or three of those saved back for "when needed"...My 5450 could use a slight pull for 5th partial E/Eb & 8th partial C (playing them open and 2nd valve would be nice) and a slight push for low C...
(I already have the "hard part" done: aligning the main slide so it glides effortlessly with NO buffing or "lapping".)

That was the most time consuming of the project. Glad you appreciated all the work. Eric needed to take the leg and 2 small branches off to get them to line up and then reassemble. Works like a trombone now. Eric did make all the braces and supports by hand. We go back to the shop tomorrow to finish the bushing and support for the upper rod to keep it from swaying. Then it all comes off for the silver plate. A local shop here will do that. Its been fun to watch an 'old world' master craftsman at work. Eric served an apprentice program with Monke in Germany many, many years ago.

I did use the F with the adjuster this AM for several Easter Services. It was so cool to be able to just pull or push on a couple of the funky notes and not have to wince when they were almost in tune. I'm thinking the bill might just resemble the "War Debt" but then it is extremely well made and worth every cent.

Update on the F tuba - tuning slide adjuster.
I was able to give the mechanism a test run tonight at a brass choir rehearsal.
It worked very well with the improvements that Eric created. His craftsmanship is uncanny.

The photo shows how the piston is positioned to drive the rod on the main slide. It has a double threaded turnbuckle to tune the horn. The piston also serves as the base for the thumb ring and the nipple for holding the 5th valve elastic.

The LH knob is offset to a position that is ultimately more comfortable. Eric fashioned a transfer rod that is angled to operate the top of the piston. The braces on the 1st valve slide were hand made and give a certain strength that absorbs any of the torgue exerted then the rod is either pulled or pushed. At first I did not realize how important that was. The entire mechanism has a hefty and solid feel to it.

Next week I take it back to the shop and it will be disassembled, silver plated and then reinstalled.

The instrument is an extremely good sounding horn and is only improved with such a device that allows you to center each pitch "dead on" without having to lip or pull a variety of slides. Now I really have no excuse for playing out of tune. It was really fun tonight to not have those nagging intonation issues. Getting used to coordinating the "joy stick" will take a little getting used to. But I am a happy camper.

I'm sure it would have been much easier to install that Reynolds tuner/piston. Making this one took about an hour for Bill Milashius on a Saturday afternoon. It is basically a piston sleeve for a trumpet before the wholes were cut. Blanks for valve caps were put on the lathe and spun down to shape. The center rod was made from a piece of stock, turned to shape, with reverse threads to accomodate a turnbuckle. Compression springs bought from the local Ace Hardware. All in all we were done before dinner. This one of course needed a few extra parts to position it on the instrument so it was comfortable to use. That is where Eric Peterson's talents as a master trumpet builder became valuable.