Sticking pistons?: cures / preventions

[ Follow Ups ] [ Post Followup ] [ TubeNet BBS ] [ FAQ ]

Posted by Joe S. on May 10, 1999 at 22:54:09:

Someone commented earlier about Hirsbrunner pistons "wearing out", and Mr. Chisham pointed out that the valvesets on Hirsbrunners and other European brands were mostly all made by the same manufacturer.

Could I offer some suggestions that might help anyone who is having trouble with these pistons on any brand of tuba?:

1/ Check the nylon valve guides for nicks and burrs. The nylon IS quiet, but bumping it on the top of the valve casings (during reinsertion after oiling) causes nicks and burrs that can drag, unpredictably, in the guide tracks of the casings. You can CAREFULLY trim away nicks and burrs with a sharp new razor blade.

2/ If any of the tuning slide braces on your instrument are "mooshed" into the body of the instrument (or into each other) from rough airline handling or your own boo-boo's, those out-of-whack slide tubes might be putting undue stress on a knuckle of a valve casing (maybe more than one), causing your pistons to occasionally hang in these now imperfect casings. Sometimes, if you push down one way with your finger, the valve doesn't stick, but if you push it down from another angle, it DOES stick. To remedy this, correct the angles of the slide tubes first (see a good repairman), and see what you have. After that, an expert lapping job will eliminate the rest of the problem.

3/ Unlike rotary valve tubas, the "York"-design piston wrap has very open shapes on the top side of the instrument. These shapes (unfortunately) lend themselves to grabbing the instrument by the slides and picking it up. Having the entire weight of the tuba resting on these slides (while picking it up and carrying it) can also warp the tubing knuckles that go into the piston casings, causing valves to stick. I suggest that those of you who have gotten into this habit replace this habit with one of picking up the tuba by its LARGE body branches.

4/ Occasionally, back pressure (from pulling slides and tuning for individual notes) can cause valves to temporarily hang up. Unlike the old wives tale, this does NOT really harm the valves nor the casings. However, this cause of piston sticking is easily fixed by venting the pistons. This means very, very carefully drilling holes in the pistons in exactly the right spots to relieve this back pressure, while having no effect on the playability of the instrument. Find a qualified repairman for this.

5/ Hey dude! Lose that "COOL" gig bag! Every time that I suggest that people "get serious" about what they are doing it really irritates someone, but those bags are NOT for serious players with serious tubas, unless you seriously are looking to get your instrument seriously dented up and end up with a ruined machine (valveset), too. Until a couple of months ago, I was "cool". I kept getting one small dink after another and kept thinking, "Oh well, that dent isn't really anything." Then, sure enough, on a crowded sidewalk outside of a theater I stepped on my own back strap. ("cool", huh?) This pulled the bag down and slammed it into a concrete parking lot partition. That dent was not "cool". Please don't counter-post will all of that arthritis/war injury/car upholstery/etc. stuff! All of us need hard cases (with large, high-quality wheels) if our instruments leave our homes. Hey, I fix all of this junk all day. I know which instruments get smashed and which ones don't. You gig bag dudes ARE "cool", but a fist-sized dent or a ruined valve casing ISN'T.

Hope this helped. Sorry about the "serious" stuff, again.


Follow Ups: