Re: Valve stems


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Posted by John Swensen on March 07, 2002 at 13:35:34:

In Reply to: Valve stems posted by IG on March 07, 2002 at 12:56:08:

I would vote for stiffer and lighter. Make them bigger in diameter, but drill them out; because the stiffness goes up as something like the fourth power of the diameter (e.g. if you double the diameter, the stiffness goes up 16 times), the lost stiffness from a small-diameter core of metal that you drilled out will be negligible. If you pressed in and/or soft-soldered an insert which you threaded for the buttons, or if you only partially drilled out the stem from the bottom, you would not be constrained by the minor diameter of the threaded hole.

You might want to perform some experiments with your brass rod, trying various internal and external diameters to see what will hold up to the inevitable bumps in store for a horn.

Nickel silver (really, nickel-bearing brass) seems much stronger and tougher than straight brass, and free-machining varieties are almost as easy to machine as free-machining brass. Texas Knifemaker's Supply sells bars and rods of free-machining nickel silver.
You might, also, want to consider aluminum stems and buttons; Bach trumpets use aluminum stems (and valve tops) with a thin brass sleeve for cosmetics. However, I doubt you would see much inertia savings going from brass stems to aluminum without, also, changing over your buttons. For a given size, by the way, aluminum is half as stiff as brass. Texas Knifemaker's Supply sells mother of pearl (wear a respirator when shaping it!), as well as synthetic versions of it, if you want to get fancy with your buttons.



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