Obtain an Instructor's Rod from an Ogre-Mage Instructor at Camp Kosh.
I just can't get my invention to work! Gah!
That's it, I've decided. I'm going to cheat and use magic.
What my invention really needs is a solid piston that's thin enough to fit through a narrow copper tube, but strong enough to withstand repeated impact without breaking. The magical rods carried by those ogre magi to the north should work perfectly.
From what I can tell, only the instructors carry the strong staves.