The physics of extending rotary spatulas.

[Tortuba]

A while a go I had the 4th rotary valve spatula extended by my service tech (I play a PT1 stencil horn). He milled a very nice looking button from brass and soldered it on. The button is about ¾ inch in diameter and 3/16 thick (my best guess). It works fine, but I have noticed that the action of the 4th valve has changed. The valve seems to return faster and hits the bumper more aggressively than the other valves. I wonder if this is due to the extra mass associated with the extension (thus the physics aspect).

I am considering having all the spatulas extended using the same type of button, to make the horn more finger-friendly to my hand.

So, my question is, will the extensions significantly alter the action of the valves due to the extra mass? Should I expect extra bumper wear because of the extra “thumpâ€

[Chuck(G)]

I suspect that the changed action of the 4th valve is due more to the spring (whatever the tech did with it) than the small mass of a nickel-sized hunk of brass. If you want to verify this, just tape a nickel or quarter to each remaining spatula and see what changes.

I wonder why your tech didn't use nickel-silver for the little extension? It would be less prone to tarnishing and blend in better with the originals. Another traditional solution is to use old silver (not fake silver) quarters for the same purpose.

[iiipopes]

More mass with the same spring will marginally (and a very, very small margin at that) slow down the action, as montre8 said. I'd be more concerned about the lengthening of the spatulas increasing the depth of travel for your fingers, especially the 4th, which is already longer on most tubas already, and therefore has the longest throw for the shortest finger.

As far as your particular instrument, it just sounds like to me the tech did his job well and threw you a freebe by adjusting and lubricating the rotor and linkage, and possibly tightening the spring to make up for the added weight, which you would not necessarily feel on depressing the spatula.

[Daniel C. Oberloh]

A few thoughts to add:

So, my question is, will the extensions significantly alter the action of the valves due to the extra mass?

I don't think the action will really suffer but the addition will lengthen the lever throw, good/bad? depends on the amount of throw and the player I guess.

I wonder why your tech didn't use nickel-silver for the little extension? It would be less prone to tarnishing and blend in better with the originals. Another traditional solution is to use old silver (not fake silver) quarters for the same purpose.

Nickel silver round bar stock is difficult to acquire in the larger sizes and a lot of repair shops don't have the thicker plate in stock and/or knowhow or tooling to cut it into nice, round, uniform discs.

Coins on tuba levers feel weird and look silly (just my opinion ).

Daniel C. Oberloh
Oberloh Woodwind and Brass Works
www.oberloh.com

[Chuck(G)]

Nickel silver round bar stock is difficult to acquire in the larger sizes and a lot of repair shops don't have the thicker plate in stock and/or knowhow or tooling to cut it into nice, round, uniform discs.

Sometimes it's just a matter of knowing where to look, Dan. Knife makers use a lot of nickel-silver in rod, sheet and bar form and small quantities are easy to obtain from them:

http://www.knifeandgun.com/catalog/nick ... oducts.htm
http://www.northcoastknives.com/northco ... plies2.htm
http://www.trackofthewolf.com/

As far as shaping, well, I guess the low-tech solution of a frame saw and file would probably work. But then, why necessarily a disc? Why not an oval or even a whole new (longer) key?

[Rick Denney]

Where’s Rick Denny when you need him????

Reading the other correct answers.

You'll have more leverage with a longer distance from the finger to the shaft. That means it will take a bit more travel and a bit less force to engage the valve. It won't affect the return at all, because that is controlled by a spring whose relationship to the valve is the same as before.

As others have said, when the work was done, the spring may have been wound an extra turn, the bumpers replaced, or the gunk cleaned out, any of which might affect the behavior of the return.

Rick "who still thinks a fresh design would put the bumpers close to the paddles instead of at the rotor shaft" Denney

[Allen]

It's interesting that Rick and Moises have both posted about innovations in musical instrument design. The mechanisms used in our woodwind and brass instruments were mostly finished by the mid nineteenth century. The last mechanism innovations in pipe organs were around the late nineteenth century.

Should we conclude: 1) Instruments reached a state of perfection more than a hundred years ago? 2) Musicians are so conservative nowadays that they will not tolerate any changes to their instruments? 3) Instrument innovations are too hard to do? 4) Instrument makers can't make a profit innovating, and thus won't do so?

I don't have answers.

Aside from possible real innovations: I have attempted to play tubas whose valves require me to hold my hand in a position that makes my wrist hurt, that have had inaccessible valve slides, etc. Just arranging the plumbing so that an ordinary human can reach the essential controls easily would be a stunning innovation!

On musician conservatism: A few years ago, I posted an inquiry on a list devoted to pipe organs. I asked if classical organists had any interest in the organ console innovations that came out of Robert Hope-Jones' innovations in the eighteen-nineties, such as stop tabs surrounding the keyboards in a horseshoe-shaped arrangement instead of draw knobs on the sides, second touch (pressing harder on a key adds some additional stops to the sound) and sustain (works like the damper pedal on a piano). There was no interest whatsoever. [Possibly the fact that all of these innovations are used in theatre organs -- with gusto -- caused negative appeal to classical organists.]

Cheers,
Allen

[Chuck(G)]

Ferree's Tools, in their periodic mailings, usually include some bit of musical arcana from the US Patent Office. Judging from the some of the weird stuff they've published, I suspect that if we're talking about mechanical linkages, it's been done.

Mo, are you talking about a tracker-sticker-backfall-roller-square system for tubas?

[windshieldbug]

Should we conclude: 1) Instruments reached a state of perfection more than a hundred years ago? 2) Musicians are so conservative nowadays that they will not tolerate any changes to their instruments? 3) Instrument innovations are too hard to do? 4) Instrument makers can't make a profit innovating, and thus won't do so?

5) If it "works" adequately already, why knock yourself out and put yourself at risk while you find out how well your innovation stands up to the test of time and shows its weakest points that you didn't take into account

or

6) Why give our overabundance of tort lawyers any reason to make you the next "hot coffee" defendant?

[Chuck(G)]

Really all I was looking for was an easy spring adjustment method. The idea of moving the bumpers to a different location came later and it really didn't stay in adjustment in the linkage position.

Well, you could use a straight threaded rod for the "sticker", put a coil spring in the middle, braced against a fixed stop with nut bearing against the other spring end for adjustable tension, then have the bumpers as nuts on the same rod on either side of another fixed bumper.

But I think I've seen that setup in about 53 million other places...


I kind of like clockwork springs myself--they're about the nearest thing you can get to a constant-force spring.

[Daniel C. Oberloh]

Nickel silver round bar stock is difficult to acquire in the larger sizes and a lot of repair shops don't have the thicker plate in stock and/or knowhow or tooling to cut it into nice, round, uniform discs.

Sometimes it's just a matter of knowing where to look, Dan. Knife makers use a lot of nickel-silver in rod, sheet and bar form and small quantities are easy to obtain from them:

http://www.knifeandgun.com/catalog/nick ... oducts.htm
http://www.northcoastknives.com/northco ... plies2.htm
http://www.trackofthewolf.com/

You got me all in a lather for nuthing. Thanks Chuck but plate and rod is not a problem, I was refering to 1/2'' 3/4'' 1'' round bar stock nickel-silver (my sources have dried up ), Oh bother! The search continues.

As far as shaping, well, I guess the low-tech solution of a frame saw and file would probably work. But then, why necessarily a disc? Why not an oval or even a whole new (longer) key?

(sigh) Yeah, you are right. I have just seen too much of what looked to be cut with a hammer and straight chisle that it bugs me just a tad. A couple easy to make fixtures on a lathe sandwitching the plate makes a real straight, uniform and round disk in serious hurry. Keeps the cost way down too while producing a nice looking final product. New longer key? sure, why not? its only money.

Daniel C. Oberloh
Oberloh Woodwind and Brass Works
www.oberloh.com

[Art Hovey]

By extending the paddle on a rotary valve you also lengthen the stroke of the finger that moves it. (I have done this on three different tubas.) The result is that the valve feels less sluggish, and more like a piston valve. I like that because I am accustomed to pistons. At the same time, you are adding some mass to the system, which could explain why it thuds harder on the return stroke. (The spring could have been tightened up too.) For best results the mechanism should be as light as possible, but still strong enough to do the job reliably. On my "frugalhorn" project I used hollow tubing for the linkage where possible.
Another way to lengthen the finger stroke is to increase the distance between the rotor axis and the point where the pushrod connects to the rotor. In addition to making the action feel lighter, this will reduce the force exerted on the rotor bearings, so they will wear out less quickly. Finally, by increasing the distance from the rotor axis to the bumpers and by using a softer bumper material you can get a more precise yet quieter action.
The latter two suggestions are not easy to do as modifications, but should be considered by anyone who is redesigning a rotary valve system or building one from scratch.

[DonShirer]

The earlier replies were more correct. Adding mass to the key will slightly reduce the velocity with which it hits the stop, but the energy it takes to stop it is exactly the same, since (neglecting friction) the kinetic energy of the moving key would then be equal to the energy stored in the spring during compression.

If the "thud" depends on that stopping energy, which seems reasonable, the only reason it would increase is (as others have said) because the spring has been tightened, less friction, etc., thanks to the technician.

[iiipopes]

The modification I want to see to a rotor bar involves the 4th valve as well, being the longest rotor assigned to the shortest finger. So why do all four rotors have to share the same spindle? Braze two more circles to the 4th valve spring guides outboard of the existing ones, then have a secondary spindle only the length of the width of the added guides. Bring out a shorter paddle to this set of guides, make the link to the rotor the tad longer necessary to balance it out, and readjust spring as necessary. I believe it would be much less stress on the pinky to get a slightly shorter paddle all the way out to where a pinky actually is in relation to the rest of the hand, not that expensive to do, and since the entire bar is screwed on the nest, relatively easy to revert to total stock if need be.

[Allen]

All this talk of innovations and no one has suggested electrifying the valve action? Just think, your fingers operate keys that are merely electric switches, and electrical actuators do the actual work of making the valves operate. Then, the valves can be placed wherever it's convenient for forming the plumbing, and the set of keys can be placed wherever it's convenient for the hand.

Of course, we don't have to stop there. How about an automatic (microcomputer-controlled) mechanism to pull slides? Every tuba can have perfect intonation!

I have even more deranged ideas, but modesty prevents me from overwhelming all of you with them.

Innovatingly yours,
Allen

[Dan Schultz]

All this talk of innovations and no one has suggested electrifying the valve action? Just think, your fingers operate keys that are merely electric switches, and electrical actuators do the actual work of making the valves operate. Then, the valves can be placed wherever it's convenient for forming the plumbing, and the set of keys can be placed wherever it's convenient for the hand.

Of course, we don't have to stop there. How about an automatic (microcomputer-controlled) mechanism to pull slides? Every tuba can have perfect intonation!

I have even more deranged ideas, but modesty prevents me from overwhelming all of you with them.

Innovatingly yours,
Allen

After having spent 30 years designing automation machinery, I can tell you that it's all been done in one form or another. Sure, it's possible to manipulate the valves with solenoids and air cylinders, but one would have a real problem 'half-valving' or doing a gliss. I suppose even that problem could be overcome by using expensive servos. Why would anyone want a tuba to have perfect intonation, anyway?!

[windshieldbug]

Of course, we don't have to stop there. How about an automatic (microcomputer-controlled) mechanism to pull slides? Every tuba can have perfect intonation!

Ah, there's the rub- Perfect intervals, Equal Tempered, Pythagorean, Meantone, Just, with what base as a start, along with the harmonies behind... I think your "simple" system just got a lot more complicated than just using your ears and push/pull!

[Allen]

Of course, we don't have to stop there. How about an automatic (microcomputer-controlled) mechanism to pull slides? Every tuba can have perfect intonation!

Ah, there's the rub- Perfect intervals, Equal Tempered, Pythagorean, Meantone, Just, with what base as a start, along with the harmonies behind... I think your "simple" system just got a lot more complicated than just using your ears and push/pull! :shock:

I'm making nice deranged suggestions, and all you're seeing is problems! Of course tuning is complex. Just think of all of the software development opportunities that makes. And the best feature is that you can blame the computer for all mistakes. [Of course, the software developers will blame the users for not using the software correctly.]

It seems to me that people are using mere practicality to get in the way of the spirit of true innovation.

Cheers,
Allen
[Now I'll remove tongue from cheek.]

[windshieldbug]

Just think of all of the software development opportunities that makes

Sharp - Operator error.
A ≠ 440 - Next release.
Flat 5th partial - Feature.

[iiipopes]

All sorts of actions have been tried on pipe organs; if physical placement due to the size of the instrument or location of the architecture are not an issue, a lot of manufacturers have gone back to direct mechanical linkage tracker: overall easier to maintain, lasts longer, less extra parts to break, and control over intonation and shading that does not exist with other forms. As far as servo mechanisms: Reynolds had one on the 1st valves of tubas and other low brass for awhile with a spring return mechanism @ 1958, so you could push in for 1st valve second space C on a BBb tuba as well as pull out for 1-2 and other multivalve combinations. It lasted about as long as it took to print the brochure that described it.