Innovations you'd like to see

[harrisonreed]

Witness marks, which are on the rotor bearing plate and casing, supposedly help you figure out how much to shave off the bumpers in order to align your valve. But they don't work, at least not within a reasonable margin of error.

I don't want even a single atom of the rotor out of alignment, blocking the pathway, let alone +/- a millimeter wide sliver of it, so the witness mark should be hairline thin.

[BGuttman]

...

What's a "witness mark"?

Witness marks are engraved lines on the rotor to help with the alignment. You can see them if you remove the large cap on a rotary valve. The bearing plate has a notch on the edge and a scribed line on the end of the bearing that takes the valve stem. The notch has to line up with a notch on the casing. The rotor stem has two scribed lines on a 90 degree angle. When the scribed line on the valve stem lines up with the scribed line on the bearing plate (and everything else is lined up) the valve should fit perfectly aligning the rotor to the ports.

Witness marks are often used to shave bumpers to fix alignment, although with the advent of inexpensive borescopes it is better to adjust the valve by looking inside at the ports themselves.

[ericcheng2005]

...

Bumper pads that are silent, not squishy, and don't compress even after 100 years of non-stop valve activation.
...

Sounds like you may want polyurethane. Lots of hardnesses available to get what you want it to feel like.

What's a "witness mark"?

The little notches under the rotor cap on the bearing plate that show you whether the rotor is aligned or not

[whitbey]

Yes on the bumper pads!
Yes, I can make my bumpers work and last for several years, but it is a pain because the system is a bad design and has to be horsed to work.

[baileyman]

A mechanic I think would look at a rotor and think it needs a couple of high and low limit set screws with locking nuts. Further, perhaps an alignment drilling where a specific bit size would pass through the casing into each of two holes in the rotor indicating best alignment. And cinch up the set screws, which would operate limits padded by polyurethane.

[BGuttman]

The system we have now is VERY old. I have played Civil War era instruments with rotary valves using the same system (but cork bumpers instead of rubber). The system you describe is going to be more expensive to implement even though it might be better.

[harrisonreed]

So is this a thing? I want exactly that. If that is too expensive I at least want quiet bumpers that won't begin to compress before The rotor core itself actually disintegrates, long after I am dead.

[JohnL]

Harrison, how about rotor valves that are consistent enough from unit to unit that replacing a bumper consists of just pulling the old one and plugging the new one in - no need to trim. That might be easier to achieve. Rather than "forever" bumpers, you just need bumpers that are cheap and easily replaced.

[tombone21]

A valve bumper mechanism with limit screws could be a really, really good idea.

[2bobone]

I proposed that very thing a couple of years ago and even provided a diagram. There was no interest.

[hornbuilder]

2bobone.
Shoot me an email.
[email protected]
Interested to see your thinking.
Cheers
M

[ithinknot]

I proposed that very thing a couple of years ago and even provided a diagram. There was no interest.

I always wondered why rotors didn't have set screws for alignment. From a mechanical perspective, this would obviously be superior, and the implementation would be extremely straightforward.

Once I became seriously involved in the making/restoration/servicing of musical instruments (not brass, but that's another story) I soon learned why. Anything that can be fiddled with will be; any screw will eventually be turned. Rubber bumpers lose accuracy over time, but in a gradual and predictable way. A loose screw, or a user with some loose screws of their own, can wreck the alignment immediately.

Adjustability is great news for those who demand the highest level of mechanical performance AND have the time and interest to learn to calibrate equipment accordingly. Charitably, let's say this is 10% of users. Of the remainder, a small but honourable number recognise the limits of their own skill and understanding, and leave well alone. The vast majority of semi-informed knob twiddlers will dive straight in with a poorly fitting screwdriver, chewing up the screw head in the process, and improving nothing. In time, some will learn, but plenty of instruments will be left playing in a way that will be assumed to reflect poorly on the maker/local tech/anyone else. As such, making adjustment a moderate PITA is a reputational insurance policy for manufacturers.

If you're a high level user and tolerably dextrous, then you could very easily learn to align your own rotors, especially now that the Amazon is lush with $10 borescopes. But the minimal investment in time, razor blades and spare bumpers deters a lot of potential disaster artists.

The noise/vibration absorbing properties of the bumper material also matter: a less compressible material than rubber/polyurethane would obviously hold perfect alignment for longer, but with decreased squish comes increased clonk, so there's always going to be a balance of factors... and it may be that the current solution is the least worst.

[hornbuilder]

Consider there are those who, when losing a bumper from their rotor, will tear off the corner of their music, scrunch it up, insert, and call it "good"!! Yes. Those people do exist.

[skeletal]

Consider there are those who, when losing a bumper from their rotor, will tear off the corner of their music, scrunch it up, insert, and call it "good"!! Yes. Those people do exist.

I feel personally attacked

[BGuttman]

Consider there are those who, when losing a bumper from their rotor, will tear off the corner of their music, scrunch it up, insert, and call it "good"!! Yes. Those people do exist.

I'd do that in a performance situation as a temporary fix until I could install a proper bumper. Bumpers aren't hard to make if you have an O-ring of the right diameter.

As to the setscrew idea, you could make a replacement for the bumper holder with two bent "ears" tapped for setscrews. The screws have a threaded piece of polyurethane (probably 90 durometer) and a lock nut to allow for adjustment. I'd draw it, but would need some time (my CAD skills are pretty rusty).

[2bobone]

OK --- I rescind that statement about there being no interest in an adjustable valve bumper stop. Here is the original sketch that I drew free-handed. Sorry -- I have no CAD skills. It is a far better solution to accurate valve settings than the current "Slice & Dice" method with which we seem to be stuck.

Valve Bumper Plate.PNG

.

[hornbuilder]

There would need to be something to hold them in place, as the vibration from the stop arm hitting the bumpers "will" make them loose. Thoughts??

[harrisonreed]

OK --- I rescind that statement about there being no interest in an adjustable valve bumper stop. Here is the original sketch that I drew free-handed. Sorry -- I have no CAD skills. It is a far better solution to accurate valve settings than the current "Slice & Dice" method with which we seem to be stuck.Valve Bumper Plate.PNG.

Oh please someone make this

[tombone21]

There would need to be something to hold them in place, as the vibration from the stop arm hitting the bumpers "will" make them loose. Thoughts??

Maybe a teeny tiny o-ring, between the screw head and the bumper plate? If it's squished a bit, the pressure from the o-ring wanting o return to its shape could be enough to keep the screws from unseating themselves as the stop arm strikes. I might be way off.

Thanks for drawing this, 2bobone! This idea's got some legs now!

[ithinknot]

the pressure from the o-ring wanting o return to its shape could be enough to keep the screws from unseating themselves as the stop arm strikes. I might be way off.

No, for reliability you'd need a minimum of one lock nut on the bumper side of the tapped plate. You'd adjust the screw to position, then tighten down the lock nut while holding the screw in place. In reality, tightening the lock nut will tend to advance the screw somewhat further, so it's not necessarily a single-stage process.

You're still going to need rubber on the face of the adjustable bumper to cushion the impact and reduce noise. This material will still compress over time and require replacement, but possibly sooner than the conventional design because you'll be dealing with a rather thinner piece. When you replace (reglue?) this cover, you'll need to re-regulate anyway.

The bumper is always going to be an compromise between shock absorption and positional accuracy, and you can't have screws that are both single-handedly adjustable and immune to sudden loosening.

Anyway, as devil's advocate, trimming rubber bumpers really isn't that demanding. Compared to other players'-own cutting and scraping tasks (oboe or bassoon reedmaking, voicing harpsichord plectra) this isn't a big deal, and it's not required nearly as often

[baileyman]

On a gig, a ripped corner from a twenty dollar bill stuffed into the bumper void may work better...

The bumper set screw need not set the limit. It can snug down a purpose built limit stop. And if the proper alignment is recorded in the structure with an alignment drilling, setting the stop would be an guess-free process of aligning the holes, snugging up the stop, and then go play.

And there's no need for a better valve mechanism to look like an older one with a screw stop bit swinging around as pictured. Likely there is a much better idea out there for a talented person to find.

[2bobone]

Goodness ! There really IS some interest in this after all. My original idea was that they could easily be built with proper spacing for the screws that hold the bumper plate to the main valve body so that one could be added to any valve with ease. Either a locknut or even a "Nylock" screw could be used to keep the adjustment that is chosen. I guess one of our "tech" guys might know if there is a standard spacing for the bumper plate screws. As long as there is no groove worn into the face of the bumper pad, the pad can be adjusted in very small increments. I'm sure that there can be other ways of achieving my aim, but I thought this to be as simple as could be while not requiring any fancy milling operations. I once owned a 1929 Ford Model "A". Legend has it that when the engineers brought Henry the first carburetor design it had 12 bolts holding the bottom float bowl onto the main carburetor body. Henry, knowing that the poor quality of gasoline available at the time would require the owner to be able to dump the float bowl at any time and any place, insisted that there be fewer bolts. Twelve bolts down to six bolts and even to two bolts and Henry still said "Too many bolts" ! That is why the Model "A" carburetor has only ONE bolt that goes straight up the middle of the now-rib-reinforced float bowl. Simplicity ! It made sense then and it still makes sense today.
One last thought : I've never encountered a rotary valve, the "witness" marks of which were properly placed to directly correspond to the actual position of the valve portals internally. Never ! Let's relegate razor blades to the task for which they were designed.

[harrisonreed]

If the rubber compresses a bit with this new system though, couldn't you just adjust it with the screw back into alignment? Then the compression is mostly over, and your rotors are aligned. Or, again, use a material that barely compresses.

[BGuttman]

If the rubber compresses a bit with this new system though, couldn't you just adjust it with the screw back into alignment? Then the compression is mostly over, and your rotors are aligned. Or, again, use a material that barely compresses.

If we go for little compression we get more clanking as the stop arm hits the stop. Softer stops mean less noise. We could find a material that doesn't compress permanently but is soft and that might be the ticket. I think of polyurethane rubber of about 90 durometer (I had some screen printing squeegees of this material and they retain shape pretty well).

[harrisonreed]

I'll leave the science to the scientists. It sounds like this is all possible, and would be practical if consumers refused to compromise on this.

[2bobone]

I learned during a period when I worked as a piano technician, that rotary adjustments can acquire a "groove" over a period of use so that when you make what you think to be a slight adjustment, it is really a big adjustment. Visualize a flathead screw and then imagine what happens when a part of the mechanism that usually falls directly into the slotted portion of the screw, is required to fit into the surface presented to it when the screw is turned even so little as 1/32nd of a turn. Now, that part is hitting the flat surface of the screw face and is no longer in the grooved portion as before. You've only made a 1/32nd turn but you've got a huge difference in point of reference. It would work perfectly for initial calibration, and should the rubber bumper acquire a deep groove, one need only glue on a new bumper. A 180 degree turn of the screw would place the part of a mechanism back in the previous groove but a bit higher or lower to the point of reference. Simple and cheap. I hope my explanation is clear.

[hornbuilder]

I'm afraid there is no standardized bumper plate hole spacing between manufacturers. Also the holes themselves, and the size of the bearing "chimney", as well as the radius of the stop arm come into play.

[Dennis]

One last thought : I've never encountered a rotary valve, the "witness" marks of which were properly placed to directly correspond to the actual position of the valve portals internally. Never ! Let's relegate razor blades to the task for which they were designed.

I have one, but they are only aligned because one was 90 degrees out. When I had the horn overhauled, Jim Patterson aligned things with a borescope. He used one of the existing witness marks, and used a file to make a new witness mark.

[2bobone]

I would like to have been one of the "witnesses" who "witnessed" Jim Patterson "witnessing" the filing of a new "witness" mark !

[Kevbach33]

With regards to the tuning slide area, ferrules should not interrupt the tubing. Granted, this makes more sense on traditional (Bach style) tuning slides, but I think it could be useful on reverse (pardon, FORWARD, like Conn) slides as well. Why should the air and vibrations have to go through tubing, then a ferrule, then tuning slide legs, then another ferrule, and then the bow (...and then another ferrule, then tuning slide legs, then ANOTHER ferrule, and then the bell)? It should be tubing, then tuning slide legs into bow into tuning slide legs, then a ferrule, and then the bell (since turning a conical bell with a cylindrical tuning slide leg might be fairly difficult, also modularity...). The ferrules on the tuning slide would be there to prevent jams.

Edwards had explained this concept on their now discontinued gen II trumpets.

Of course, this does mean the slide legs would be the same material as the bow instead of the common yellow brass or nickel silver (i.e. rose brass bow? Also rose brass legs), and one can only guess what effect, positive or negative, that will have on the sound.

I know at least one small maker does this general idea for Bach tuning slides, but maybe truly one piece tuning slides should be more widespread for those seeking less turbulence.

[BGuttman]

Small comment: Rose brass is not nickel silver. Nickel silver is an alloy of copper and nickel which is not yellowish in color. Rose brass is an alloy of 80% copper and 20% zinc.

[hornbuilder]

Kevbach33.

You're assuming that designers don't consider what is happening underneath the ferrules. Now admittedly some designs do not seem to take that into consideration a great deal, but rest assured there are some that do!!