bent Jupiter sousaphone piston
Posted: Wed Jun 10, 2026 5:38 pm
I just bought a bunch of this and that from KHS (Jupiter) over in Mt. Juliet (east end of the Nashville megalopolis) They don't have any replacement #1 pistons in stock, and - unlike a few years ago - the price has become pretty fancy anyway.
This sousaphone's #1 piston was banana-ed.
I don't care for setting instruments aside (particularly elephantine instruments) marked "waiting on parts". I also don't have time to send this valve section off to one of the shrinking members of the piston rebuilding community, particularly when it would cost several times the cost of a brand new piston to have one of those people rebuild this piston (and it probably wouldn't be repaired any sooner than a new replacement piston would eventually arrive anyway)
..so what I did was to push the piston in from the bottom (the top wouldn't do any good, because the fitment area doesn't begin on the top side until about an inch down within the casing) and gently pushed the piston in until it barely began to bind.
I pulled it back out, held a straight edge up to the side of the piston (turned to the side that I suspected was concave), held it up to a light, and verified what I suspected. I inserted the piston back in to the same depth, and whacked the top edge fairly smartly with a rubber mallet (so as to remove the curve from the piston). Being a stainless steel piston, it took a few whacks until I got it the best it could be (at least going up and down in the casing, but dragging). After that, I started paying attention to contact points. I took a very very fine tooth file - that is wide and flat - and removed all of the high points which were causing the drag.
Yes, there are those hollow steel appliances in which Pistons can be placed whereby the repair person beats the crap out of the hollow steel cylinder, but those are not cheap and there's only about 200 or 300 different encountered piston diameters (down to the thousandth of an inch).
I then took the file marks out with medium grit sandpaper, worked that grit down to about 600, and - rather than burning time with subsequent finer grits - I cut to the chase and carefully polished out the 600 grit on the buffing machine.
I did all that (other than the buffing) while sitting down in a chair.
I did not "lap" the piston into the casing. In other words I didn't warble out the casing to accommodate the (now: perfectly functional yet obviously still imperfect) piston.
If they still want to, they still have an option of having me purchase a replacement #1 piston - YET with me having not having compromised the casing in the least.
Here are the results:
It goes up and down just as reliably as do the others, and offers quite an impressive vacuum release: (dry, no oil)
This one also had a bunch of green etching around the bottom branch, which resulted in stripped away silver underneath that green corrosion.
100% of the time - when I scrape this stuff off, I know that someone pissed on the instrument. (Ha-ha big joke
) Things are "different", these days... History scholars (40 and 50-year-olds who want tell us how things were 60 and 70 years ago) tell us there's much less crime and much more respect for our fellow man, today, as well as much less pissing on silver sousaphones today, I suppose.
It's dinner time, I've done all of this school's Jupiters.
Remaining for this school are two short-action Conn's and three Kings.
I need these 13 out of here, because another school has 14 that need to come in from a trailer and be put where these are now...
and another school and another school...
NEXT !!!
This sousaphone's #1 piston was banana-ed.
I don't care for setting instruments aside (particularly elephantine instruments) marked "waiting on parts". I also don't have time to send this valve section off to one of the shrinking members of the piston rebuilding community, particularly when it would cost several times the cost of a brand new piston to have one of those people rebuild this piston (and it probably wouldn't be repaired any sooner than a new replacement piston would eventually arrive anyway)
..so what I did was to push the piston in from the bottom (the top wouldn't do any good, because the fitment area doesn't begin on the top side until about an inch down within the casing) and gently pushed the piston in until it barely began to bind.
I pulled it back out, held a straight edge up to the side of the piston (turned to the side that I suspected was concave), held it up to a light, and verified what I suspected. I inserted the piston back in to the same depth, and whacked the top edge fairly smartly with a rubber mallet (so as to remove the curve from the piston). Being a stainless steel piston, it took a few whacks until I got it the best it could be (at least going up and down in the casing, but dragging). After that, I started paying attention to contact points. I took a very very fine tooth file - that is wide and flat - and removed all of the high points which were causing the drag.
Yes, there are those hollow steel appliances in which Pistons can be placed whereby the repair person beats the crap out of the hollow steel cylinder, but those are not cheap and there's only about 200 or 300 different encountered piston diameters (down to the thousandth of an inch).
I then took the file marks out with medium grit sandpaper, worked that grit down to about 600, and - rather than burning time with subsequent finer grits - I cut to the chase and carefully polished out the 600 grit on the buffing machine.
I did all that (other than the buffing) while sitting down in a chair.
I did not "lap" the piston into the casing. In other words I didn't warble out the casing to accommodate the (now: perfectly functional yet obviously still imperfect) piston.
If they still want to, they still have an option of having me purchase a replacement #1 piston - YET with me having not having compromised the casing in the least.
Here are the results:
It goes up and down just as reliably as do the others, and offers quite an impressive vacuum release: (dry, no oil)
This one also had a bunch of green etching around the bottom branch, which resulted in stripped away silver underneath that green corrosion.
100% of the time - when I scrape this stuff off, I know that someone pissed on the instrument. (Ha-ha big joke
It's dinner time, I've done all of this school's Jupiters.
Remaining for this school are two short-action Conn's and three Kings.
I need these 13 out of here, because another school has 14 that need to come in from a trailer and be put where these are now...
and another school and another school...
NEXT !!!