Valve section bore discrepencies

[joh_tuba]

This is a topic that 'those in the know' are likely aware of but I doubt any one of us are aware of all examples or how often it actually happens.

In the past I've noted that on at least one example of a Willson 3050 Piston CC tuba had a smaller bore valve(with corresponding smaller tuning slide) in the middle of the valve section.

I've also heard rumors that MW6460 Kodiak F tuba makes use of similar 'tricks' to adjust response or intonation.

Just recently I took a micrometer to a MW2145. The piston valve block is 19mm, and the rotor valve *immediately* after the valve block is 20.5mm. HOWEVER, the tuning slide immediately after the rotor is 20mm and tapers to 21mm on the big side.

I doubt it's a mistake and after spending some time studying the 2145 I see why they didn't place the rotor after the main tuning slide. It would be a very tight fit and perhaps this was a compromise solution?

Thoughts?

Other similar examples?

[joh_tuba]

1) Meinl Weston tubing is built EXTREMELY precise such that if you order 19mm and 20mm they will 'telescope' inside one another.

2) You can take any main tuning slide from any B&S F or PT rotor tuba from the last 30 years and swap them around and they will all 'just fit'. Someone built a jig years ago and it still works.

3) In the world of tubas and valve alignment, there are players that would *definitely* notice if a valve were 0.5mm out of alignment. That's not an insignificant amount.

There is no reason to think it's an accident when a horn leaves the factory with this 'feature'. Whether it makes it play better OR those are the parts that fit the easiest, it's almost certainly a conscious design choice based on some perceived benefit.

[cjk]

sorta related to having bigger than smaller then bigger valves:

viewtopic.php?f=2&t=33949" target="_blank

[windshieldbug]

How many slides does your average tuba have? So how many bore jumps smaller<bigger>smaller does it have? How much percentage conical/cylindrical does it have per valve combination? How about any mouthpiece/gap?

The effect may just be in your head, but then again, a lot of playing performance is in your head, too...

[joh_tuba]

How many slides does your average tuba have? So how many bore jumps smaller<bigger>smaller does it have? How much percentage conical/cylindrical does it have per valve combination? How about any mouthpiece/gap?

The effect may just be in your head, but then again, a lot of playing performance is in your head, too...

All your points are well taken. There are plenty other worse offenses to the continuity of the taper progression in tubas. It's easy to perceive differences that don't exist OR ascribe actual differences to the wrong cause. Sometimes this stuff matters and sometimes it's meaningless. Plenty of examples of models that have changed quite dramatically over the years(Miraphone 186) and still basically the same horn and others that are clearly different beasts with a small change(MW2165 variations, PT9 vs PT10, MW2000 vs 2155, etc)

Acknowledging all of that:
My purpose was to point out an interesting design 'feature' that:
1) Appears to be more common than we are aware.
2) Is *not* advertised as a feature. Perhaps for fear of messing with perceptions of how the instrument plays. We agree, a lot of this can be in our head.
3) Is obviously not arbitrary.. someone chose to do it for a reason.. which reason.. who knows.
4) As Bloke put it, "hmmmm"

[Three Valves]

I build pipe organs for a living, and our normal working tolerance is 1/32".
0.5mm seems a nominal difference to me.

That's interesting.

We go to Longwood Gardens and to the old John Wanamakers whenever we get the chance. (I'm from that area)

Of course, I sit as close to the big wompin' pipes as I can!!