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Sorry, piston

Actually, 20mm seems pretty standard these days on the 4th valve. The other 3 valves are 19mm.

58mark wrote:I guess I'm old school. It used to be you never saw a piston set Larger than 750 to prevent the valve stroke from getting too long

I'm definitely old school, too

The older Bauerfeind (and Böehm & Meinl too) valvesets were 19mm/.748 bore through all 4 valves, but at some point they seem to have transitioned into this larger 4th valve scenario.

Ideally... the entire tubing length should be conical. But then... you couldn't have adjustable slides, could you?

Courtroise messed with the concept of have NO tuning slides. that idea wasn't so hot during a time when the industry couldn't even settle on a standard for pitch.

Dan Schultz wrote: Courtroise messed with the concept of have NO tuning slides. that idea wasn't so hot during a time when the industry couldn't even settle on a standard for pitch.

That was Couturier, and each horn came with 3 slightly longer main tuning slides to keep the cylindrical length to a minimum... but on most horns the valve slides were fixed so that they could continue to increase in diameter THROUGH the valves...

I've got to think that there's a specific reason (other than just being an opportunity to expand the bore) that these horns have a dual bore MTS. I mean, that tiny amount of expansion (roughly .040) could easily be incorporated into one of the several other branches, couldn't it?

After all, it must take a lot more trouble to make a crook with an expanding bore, where a crook with all the same bore would be much easier and convenient...?

BTW, the only piston tuba (not sousaphone) that I've ever seen without a dual bore MTS was a small bore (.656) Conn (not sure of the model, maybe the 14J?)

It would be so cool if those folks that did all the R & D "back in the day" were to have written down the reasons why they settled on what they did.

It would be even cooler to go back in time and pick their brains.....

I'm assuming the only way to truly know the answer to my question is, in the words of York-aholic, is to "tack it together and see how it plays" Personally, I'm simply too lazy to reinvent the wheel....

I think what I'll do is use an MTS that is 20mm/21mm, and then cut the dogleg further up the taper, at a point that will be equal to 21mm, or expand it slightly to accommodate 21mm at the present end....

Short of that, if any of the gurus out there have a method where a 19.5 mm tube can be affixed to a 20 mm knuckle, I'd be greatly appreciative to find out what it is

???

roweenie wrote:If the King you're referring to is the 2340/1, I beg to disagree (I can't speak to the sousaphone).

Point taken. I'm older than that. At least the older souzys does have a "down and back" main tuning slide before the valve block.