piston weight

[Dan Schultz]

When you say 'East German'... are you speaking of the 70-ish Bohm & Meinl .751" bore pseudo-Yorks... aka Marzan tubas? I can measure up one of those pistons and give you a weight in grams if you like.

[Dan Schultz]

all of the B&S/M-W stainless steel pistons...as well as other German-made stainless steel pistons

That's what I thought. The B & M/Marzan pistons are conventional brass with nickel plating.

[iiipopes]

OK... real thought...

To bond the knuckles to the stainless requires higher heat. Higher heat increases the the possibility/probability of distortion of the piston walls. End result could a lapping nightmare. The thicker wall stock will be more stabile and distribute the heat more evenly resulting in less/little/no distortion.

Another reason I have never liked stainless pistons

[Art Hovey]

It can be done.
The Mirafone 1271 (now 1272) has super-light stainless-steel pistons.
The Nirschl "big valves" are super-heavy. But oddly enough, the knuckles inside those giant pistons are super-thin and soft.

http://greatctjazz.org/Sugarfoot/

[Bob Kolada]

Too bad that 1271 sucks.



Bob"still waiting on manufacturers to make simple, easy playing, affordable, comfortable horns//where's my $4k new 5 front valve Eb with quick valves, good intonation, and COMFORTABLE ergonomics"Kolada

[SousaSaver]

OK... real thought...

To bond the knuckles to the stainless requires higher heat. Higher heat increases the the possibility/probability of distortion of the piston walls. End result could a lapping nightmare. The thicker wall stock will be more stabile and distribute the heat more evenly resulting in less/little/no distortion.

Another reason I have never liked stainless pistons

In my opinion the stainless tends to hold up better than most metals when heated to that degree. It doesn't behave like brass or nickel at brazing temperatures. Plus, Brian is right, there are many more steps between brazing the tubing in and finishing the piston.

[joh_tuba]

In my limited experience a quality nickel plated valve is preferable to any other piston valve material.

Nickel is much more 'slippery' and if a quality plating job is done it will last a LONG time.

[Paul Scott]

I pulled out a .750 bore York and the valves certainly are light...BUT I'm truly amazed at the pistons on my 1930 Buescher sousa: they are even lighter (truly featherweight) and are accommodating a bore size pushing .770! The piston walls are very thin. If I discover a method of weighing them (postage scale perhaps?) I'll post the results.

[Dan Schultz]

..... I can also whip up a little GD&T work up for the piston surface......

I spent 30 years in manufacturing. I thought that was a long forgotten term. Functional gauges and everything? I've been away from the field for almost ten years now and am happy that someone still knows the terminology.

I think lack of this sort of detail is what causes problems when something is just copied and not prototyped/researched.

[Art Hovey]

A good part of a tuba piston's mass is in the top plate, where the stem screws in. It is usually a thick chunk of brass to provide a solid anchor for the the stem. Some careful engineering and machining could cut down on that mass significantly.

http://galvanizedjazz.com/

[imperialbari]

So now you can get pistons in your school colours?

[Rick Denney]

A bit of discussion of the materials might help.

Stainless steel is regular iron-based carbon steel, but with enough chromium in the mix to allow passivation. Passivation occurs when a protective layer of oxidation forms on the surface, preventing further corrosion. The chromium percentage has to be at least about 14% to provide passivation. Nickel is also added to the alloy so that the steel will retain its Austenitic crystalline structure, which is important for strength.

Monel is an alloy of nickel and copper, and is more like nickel-silver (or German Silver). Monel is mostly nickel, while nickel-silver is mostly copper. Monel is harder but more difficult to machine.

Pure nickel is not as hard as either Monel or stainless steel, but it plates easily on copper. And the brass substrate of a nickel-plated valve can be very finely machined.

All in all, Monel provides the slipperiness of nickel with much greater strength. A valve really has to be perfectly lapped to see that advantage, in my experience (and Yamaha doesn't always achieve that out of the box). But it is the most expensive of the choices by far. I suspect that stainless steel is a cost-saving alternative to Monel.

It seems quite likely to me that modern valves are made thicker to allow more automation in machine work after the valves are brazed together. The thinner the wall initially, or the thinner it is machined down to, the more demanding the production precision. I suspect that was Bloke's original point.

The best valves of any tuba in my collection are the B&M-made valves on my York Master. They have been rebuilt once, and they are really exceptional. The Holton valves are rather clunky by comparison, but I think that's because the valve body is a bit ringy. Both are nickel-plated brass. It took some real effort to make the Monel pistons on my Yamaha fast, and those valves are really picky about oil, but they have been really durable. I ought to weigh them all for comparison.

Of course, material characteristics may allow different manufacturing strategies, but that doesn't mean those advantages will be explored in any given production situation.

Rick "not sure of the value of a light piston when using a really heavy spring, as so many seem to have these days" Denney

[imperialbari]

Most monel alloys, I'm thinking, contain a little bit of magnesium.

Cool! So in a pinch I could use one of my 621 pistons with my Boy Scout pocket fire starter kit? Those things were great, but I used up all the magnesium pretty quickly...

Wade,

As long as you use a non-toxic oil: you might consider licking those pistons (during rests, etc.) to possibly discourage the onset of osteoporosis.

Alleged location is western, but this rather sounds like Chines medicine.

[Rick Denney]

...When I've removed sludge from mouthpipes/knuckles/etc. around valvesets (eliminating sticking) and refit tuba players' valvesets with springs that are "just strong enough", nearly all of them seem delighted with the change.

Most monel alloys, I'm thinking, contain a little bit of magnesium.

I can attest to your first point.

Most alloys contain a little bit of lots of things. But Monel is mainly copper and nickel, with nickel the predominate ingredient (about two thirds). German silver is the opposite--about 3/4 copper and 1/4 nickel. Plus a few other things thrown in in both cases, usually. Monel has a bit of iron, but I don't think magnesium is a major ingredient. There are varieties--it was invented in 1906 so it's been around a while.

Most of what touches the casing with a Monel valve is similar to what touches the casing with a nickel-plated brass valve. It's somewhat harder, but retains similar natural lubricity.

Rick "recalling that Besson used Monel quite a lot in the old days" Denney