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My trumpet has a "steering rod" under the main tuning slide, and on that rod there are three nuts. I wonder what these are for?

They could be used for making sure the slide doesn't fall out -- but if that was their sole purpose -- why three of them?

They could also be used for setting up a second, lower, preset tuning so that one can switch to that quickly. When would that be usable?

Would be nice to know what they are for and how to use them!

Note: The placement of the nuts is mine, and they might be intended to be placed in another sequence.

EDIT: The third nut (from the bell) is a cup nut.

EDIT: My trumpet (a Besson & Co Service Class 7255 of unknown age) produces an open Bb in tune and plays most other notes in tune when the tuning slide is placed as pictured.

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2 Answers 2

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They are to control where the stop rod actually stops the slide — thus known as a "slide stopper".

The nut closest the bell sets the actual stop point. The second nut should be turned until it is against the first nut to lock the first nut in place. To move the first nut, turn the second nut away from it to unlock the first nut.

The third nut is explained by Aaron:

The third nut serves a dual purposes of helping prevent the tuning slide from coming off, but can also be adjusted to provide a "range of motion" according to how much tuning play the performer wants. The two opposing nuts are intended to be large-face to large-face.

It occurred to me that you might not know the reason why you want to be able to control the slide stop. It's to make it possible to have fine and precise control over the position of the slide to enable accurate tuning. The way to do it is pull the slide out a little too far and then turn the first nut to slowly bring it in until it's in tune. Then lock the second nut against it.

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    The third nut serves a dual purposes of helping prevent the tuning slide from coming off, but can also be adjusted to provide a "range of motion" according to how much tuning play the performer wants. The two opposing nuts are intended to be large-face to large-face.
    – Aaron
    May 28, 2021 at 20:08
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    My third nut (from the bell) is a cup nut, so it can only sit at the very end of the rod in my case. May 28, 2021 at 20:21
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    These setups are fairly common on third-valve slides, but this is the first time I've seen one on a main tuning slide.
    – Aaron
    May 28, 2021 at 20:22
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    Great info @ToddWilcox! However the use of the slide stopper is a bit confusing for me since the thread ends long before where I would place the slide to get in tune (see edit of OP). The tuning slide is in tune when placed as in the picture. So I can't really use the nuts to tune. Could it be the instrument is intended to be tuned to a lower pitch than 440 Hz? May 28, 2021 at 20:41
  • @PetaspeedBeaver I wonder if it was put there at the factory or by some misguided previous owner? It does sort of look like the lacquer was taken off around the area where it is attached. May 29, 2021 at 3:09
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Start with a question: if you were to set the two locknuts in the middle of the threaded part of the stop rod and then push out the main tuning slide until the nuts stop the slide moving any further, what would be the new concert pitch of the open note now produced? Might it be approx concert A ?

I'm wondering whether the slide is a quick-and-dirty way of allowing you to rapidly switch between Bb and A trumpet/cornet parts without having to change instruments. The reason it's dirty is that if you push the main tuning slide out, you'd really need to slightly lengthen the tuning slide on first and third valves too.

Many manufacturers produce trumpets that do two tunings (Yamaha for instance, do a D/Eb trumpet) but the instrument is supplied with two sets of tuning slides - one set of {main tuning slide, 1st valve, 3rd valve} for D tuning, and another slightly shorter set for Eb tuning.

Having a main tuning slide that rapidly moves you into A pitch rather Bb pitch could get you out of a hole, but it's not ideal.

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