Valve behaviour query

[hup_d_dup]

I own a bunch of brass instruments. On some instruments the valve pistons do not rotate as easily as they travel up and down. I never gave it much thought.

However, I have one instrument that has valves that are very difficult to twist in their cylinders. One of these valves is so resistant that I cannot turn it using finger strength alone. All of these valves operate just fine; they are fast and seal well.

So I don't have a problem, but I am curious why this condition exists, and also what causes it in the manufacturing process?

(In my experience this condition is more likely to be present on tubas than trumpets)

Hup

[hup_d_dup]

Because the "problem" on my tuba did not affect its playability, I was not in a rush to correct it.

However, yesterday I finally pulled the valves and let them dry out. The pistons looked fine. I couldn't see into the cylinders well enough to see if there was a coating.

I cleaned the pistons and cylinders with Lime-Away and reinstalled them. The difference was striking. Whereas previously the pistons would not rotate easily (and one would not rotate at all), they now turn with minimal effort.

I did not notice a difference in the playability of the horn or the speed of the valves.

I think it's pretty clear that Bloke's diagnosis was correct.

Hup