Bollinger "cut" length?

[ghmerrill]

Suppose I wanted to modify my Gb valve to a Bollingeresque bG. How much (total length) do I need to take off? I know that the precision of any answer to this will depend to some degree on the horn involved, the tubing, the valve size, etc. I'll do the measurements and math on my own horn to get an estimate that way as well. But I'm just curious to get a rough idea based on someone who may have done this.

Of course, if I get a reasonably reliable empirical answer to this question I may skip the initial measurement and go right to the trial and error approach. I'm mostly curious at this point if I'm going to need to move braces if I have to cut my outer slide tubes.

Also -- mostly just out of curiosity -- if you've done this, did/could you do it in such a way that you could still pull to a Gb if you wanted.

[hornbuilder]

I recall seeing a document stating that the length removed should be 1", both sides. Of course when I did the specified 1" (so 2" total) the player said it wasn't enough. It seems everyone has a different idea as to where exactly that "flat G" sits between G and Gb.

[ghmerrill]

Yeah, how flat is flat if it's not Gb? And THAT may well depend on your individual instrument. But as long as you've got enough adjustment, ...

That's pretty close to my eyeball estimate. And 1" is pretty much where the bases for the cross-brace on my tuning slide are. So I'll just take that off and get the cut right, and then replace it (not sure it really needs it, but why not?)

Then I'll play with it for a while and decide if I want to swap the F and flat G slides -- which will be more exciting.

Thanks.

[hyperbolica]

The Bollinger tuning depends on the valve notes lining up in a certain position. Can't remember exactly what that was. That should give you a reference. Measure your hand slide difference between your current tuning and the Bollinger lined up tuning, and that's your cut length.

[ithinknot]

Just do the math.

Circuit length is 24 inches, minus whatever you'd like as a default tuning pull.

How much of a cut that is depends on how sharp the current Gb is... often, quite.

[ghmerrill]

The current Gb is pretty good. For normal indoor temps I usually have it pulled 1/2" or less.

[brassmedic]

Just do the math.

Circuit length is 24 inches, minus whatever you'd like as a default tuning pull.

How much of a cut that is depends on how sharp the current Gb is... often, quite.

Is that because Gb valves aren't actually Gb? Theoretically, a Gb valve loop should be 28 inches: 136 minus 108.

[Burgerbob]

I have both slides for a horn, I can measure the difference.

[ghmerrill]

Cool. One nice thing about this mod is that I can do it all in the slide itself. No need to cut the outers. So even screwing up leaves substantial recovery room.

[Burgerbob]

I'm seeing 2 1/8" difference per side.

[hyperbolica]

"Doing math" when you can't really define the "flat G" isn't going to be helpful. You're better with a differential measurement between where you are and where you want to go.

[ithinknot]

Just do the math.

Circuit length is 24 inches, minus whatever you'd like as a default tuning pull.

How much of a cut that is depends on how sharp the current Gb is... often, quite.

Is that because Gb valves aren't actually Gb? Theoretically, a Gb valve loop should be 28 inches: 136 minus 108.

Yup, because F (36.2) and Gb (28.1) combined end up slightly overshooting for D (63.4). Of course, those numbers are theoretical, based on the twelfth root of two/equal temperament, and in practice some further wiggle room is a good idea. (Where that wiggle room needs to be also somewhat depends on whether or not you tune the open horn at the bumpers.)

"Doing math" when you can't really define the "flat G" isn't going to be helpful. You're better with a differential measurement between where you are and where you want to go.

But you can choose to define the bG as an ET quartertone between G and Gb. Of course, you don't have to...


For a Benge 290 with factory G and Gb, G loop is 20.5 inches (theory says 20.4, and measuring around compound bends is not especially precise), Gb loop is 27.25 (i.e. 3.375 extenders) so short for Gb at the bumpers but combining with the F 36 to give a good D 63.25.

I made my own Bollinger extenders (1.75 legs giving a 24 loop) and it's exactly where I'd want it to be with no extra pull. If I was doing it for someone else I'd probably make it slightly shorter to have some play in the sharp direction.

[ghmerrill]

I'm seeing 2 1/8" difference per side.

Great. I will cut them a bit long and then go from there -- experimenting with where the pitches line up with/without the trigger. This seems like a relative piece of cake to me. When I cut my 1924 tuba from A=435 to A=440, it was a huge pain. Some very tight working conditions, and in those days they made really serious quality brass and double/triple silver plating.

[ghmerrill]

So ... I've been thinking and scratching my head and wringing my hands about this for the past day or so -- in part trying to figure out what I really might want. The information in this thread has been very helpful. Looking more closely at the Bollinger set-up (and at other tunings, and at the charts in Aharoni's book). I'm less convinced that this is really what I want. Mostly, I think what I want is either the Gb or G or flat-G on the thumb paddle, and the F on the finger paddle.

Then, I stumbled across this other thread (in which some of you also participated, and which I'd seen before and just forgotten), and this nice layout of the circuit lengths and how to convert from one to another: viewtopic.php?p=65015#p65015. Also, I now have in my possession both an additional replacement F slide and a replacement Gb slide.

So my current thinking is simply to change my F (currently thumb paddle) circuit to Gb (plenty of room to do this without even having to move any braces -- just some tube cutting and slide reconstruction), and move my current F slide over to the finger paddle circuit -- and this requires no modification at all, though if I like the result I will probably reconstruct the slide tubing to eliminate an excessive amount of exposed inner. That will achieve the goal of Gb on the thumb paddle and F on the finger paddle. I'll play with that for a while and then think some more. An additional advantage of this is that it's completely reversible just by swapping back to the old slides.

Kind of a science fair project.

[Dennis]

Seriously...if what you want is the G-ish valve on the thumb and the F on the finger, why don't you look into changing the linkages so the finger operates the F-attachment and the thumb operates the other valve?

[ghmerrill]

I did think of that. Making a new tuning slide was trivial (out of parts I could get). Changing the triggers to operate the opposite valves looks totally infeasible. Also, the swapped tuning slide approach is totally reversible.