Talk about acoustics!

[windshieldbug]

It's late, but I was just clued into this Pedler tuba auction.

Buescher and Pedler hooked up after Buescher left Buescher, and when he passed on, Pedler started Harry Pedler & Sons.

Buescher patented splitting the bore into two smaller tubes through the valve section so that the valve action would be quicker (kinda like Conn's oval ports). This is the first actual example that I've seen of this!



Rare Henry[sic] Peddler[sic] & Sons Tuba Elkhart Indiana No Res

[windshieldbug]

By about how much is the valve stroke reduced? And is the playing affected?

I have no experience with these, but the stroke has got to be the same as the Conn short stroke oval-port valves. I'm sure we've both played those, and they sounded fine (for a Conn) to me. The bore here is split all the way through the valves. This just blew my mind, so I thought I'd pass it on!

[Chuck(G)]

It improves things some, but not as much as you'd think.

Consider, for example, a bore of 0.750" The cross-sectional area computed by A = πr², or about 0.44 square inch.

Now, one divides this into two, so a bore with one-half the cross-sectional area is about 0.53". While this sounds really good, it saves only 0.22" in the valve stroke.

It's an improvement, but not much of one--and I wonder how much the sound is affected.

The same problem attends with the Conn system (actually, folks were ovalizing valve ports back in the 19th century and Holton was using ovalized ports in the 1930s on their big horns). Consider the same 0.750" bore and suppose that you wanted to reduce the stroke by half, or 3/8".

Well, the area of an ellipse is πAB, where A and B are the major and minor radii. So, if A is 0.375", then B must be about 1.50"! So keeping the same cross-sectional area by halving the stroke results in a valve port width of 1.5", making for very large piston. In practice, this level of ovalization is rarely used, but you get the idea that thee ain't no such thing as a free lunch.

[Chuck(G)]

Most all of those rotary valves (mostly trombone, but occassionally tuba) that appear to keep the same bore throughout the rotor are little more than optical illusions (marketing gimmicks?)

Everyone, it seems, wants to believe something. A couple of weeks ago, I was listeningt o a horn player go on an on about how wonderful vienna valves were.

'Guess that's why you see so many of them.

[windshieldbug]

What I find interesting is that two of Buescher's patents are diametrically opposed;

His "Epoch" valve system of 1901, which claimed to keep the bore constant through the valves:



and the split/duplication of windway patent of 1926



BTW Chuck, I do have an Allen valve cornet from the 1800s, and it sounds like... a cornet!

[Chuck(G)]

and the split/duplication of windway patent of 1926

Maybe (or maybe not) it doesn't matter so much on a tuba, but I could see the split system on cornet having all sorts of acoustic problems.

'Guess that's why you see so many of them...

You could try a completely split system tuba with two completely independent branches ending in two bells...

[SplatterTone]

You could try a completely split system tuba with two completely independent branches ending in two bells...

Put a rotator on the bells and get a Leslie tuba. Way cool. The jazz guys would snap those up immediately.

[Chuck(G)]

BTW Chuck, I do have an Allen valve cornet from the 1800s, and it sounds like... a cornet!

I've seen an Allen valve tuba, too. Now, from a practical standpoint, that actually makes some kind of sense.

(For those uninitiated among you, an Allen valve is a rotary valve with strongly ovalized ports, leading to a much smaller in diameter, but taller rotor than usual)

Since the weight of a rotor goes up as the cube of the radius, it definitely results in a much smaller rotor (and lighter) rotor. The Holtons I spoke of earlier, essentially take an Allen valve and "unfold" it so instead of rotating, the valve body moves up and down. The "spaghetti" between the valves is almost as bad as the Pedler tuba shown.

Curiously, there's also an "Allen valve" for steam locomotives--it's benefit is--a short stroke. Doesn't look anything like its musical counterpart, though.

[windshieldbug]

You could try a completely split system tuba with two completely independent branches ending in two bells...

In my impulsive youth, I made a trumpet mouthpiece with two joined shanks (past the throat). I thought I'd get two trumpets ala Kirk. What I got was a narrow-bore, quarter-tone baritone!

(but I go for a Leslie tuba, particularly if the bells would spin!)

[windshieldbug]

an Allen valve is a rotary valve with strongly ovalized ports, leading to a much smaller in diameter, but taller rotor than usual...
Since the weight of a rotor goes up as the cube of the radius, it definitely results in a much smaller rotor (and lighter) rotor.

The rotor IS taller, and thinner. The advantage in playing doesn't come from the thinner diameter (and less movement), but from the less weight (and quicker movement).

It's noticible on the cornet, so people can imagine the advantage on the tuba (just as a "built-up" rotary valve reduces weight and improves action)

[windshieldbug]

...steam locomotives...musical counterpart...

Are we back to discussing the viola again?

Maybe. Makes me think of a viola solo...

<img src="http://www.micro-blaze.com/graphics/devine.jpg" width="300">

[Chuck(G)]

The rotor IS taller, and thinner. The advantage in playing doesn't come from the thinner diameter (and less movement), but from the less weight (and quicker movement).

Back to maths, I suppose, I spoke a bit eliptically ( ), but basically here's the reasoning:

If one takes a round-ported conventional rotor, the weight is rougly proportional to the cube of the bore, as the volume displaced by such a rotor for a given bore b is:

b(πb²)

That is the height of the cylinder times the area (essentially the size of the bore plus a bit is both the radius and the height of the rotor).

Now, suppose that we halve the diameter of the rotor but double its height. The cross-sectional area of the port opening is the same, but the volume is now:

2b(πb²/4) or

b(πb²)/2

Or half the volume--and half the weight. Note that, on the other hand, an ovalized-port Conn short-stroke valve reduces the height of the cylinder described by the piston and increases the diameter, resulting in the opposite effect--a heavier valve, albeit one with a shortened stroke.

Howzat?

[Daniel C. Oberloh]

I can just see someone sending that thing off to Oberloh and insisting that he make a "matching" 4th valve for it.

Yikes!!!

Thanks but NO. I have enough on my plate for some time to come.

I am sure someone else could find a way to stich a spare Mirafone rotor on it some place.

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

[Lew]

Well, since Mike Lynch bought it I doubt he's going to be adding a 4th valve, so I think you're safe for now.

Mike, let us know how it plays...