ok...removing rotor vertical play (blokeskool)
Posted: Sun Jan 02, 2022 4:11 pm
I've offered to talk some/any-one through replacing a Bach trombone upper inside slide tube (on the phone)...
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I'm going to go ahead and post how (bloke) removes rotor vertical play.
Those who have better methods may denounce/condemn/laugh.
ok...
When the REMOVABLE rotor bearing has a LIP (which SITS ON the back of the casing), all I do is to grab a saxophone tone hole file (WIDE/EXTRA-FINE "TEETH"), file down the back of the casing (maintaining 100% contact the entire time), and continue to re-try to rotor-and-bearing UNTIL the up-and-down play has been eliminated. I like to file N-S for a bit and then file E-W for a while (or NW-SE / SW-NE...depending on what stuff might be in the way). Changing the direction of the strokes gives me feedback as to whether I'm "digging" in too much on one particular side of the casing opening. Again...It's important to try the rotor/bearing every so often, so as to not take away too much material...but - if slightly too much material is removed - that's not unlike MANY brand-new rotor assemblies, so...
When the REMOVABLE rotor bearing sits down IN the casing on a LEDGE (ex: MIRAPHONE), well...I have to fire up the lathe. I mount the outside center of the removable bearing into the head stock (barely more than "just" tight enough to hold it) and turn down the outside edge of the UNDERSIDE surface (the surface which faces the rotor body) of the bearing. Cutting in only a millimeter (as those ledges are so narrow) is enough, but I might cut in as much as 4mm...[1] carefully "dig in", then [2] pull back to the edge. I BARELY shave them and test them OR (as it's actually possible to measure the up-and-down travel) sometimes I trust the marks on my lathe and shave them down about .001" LESS than the amount that I measure (in vertical play). .001" less (sometimes) is "not quite enough" and (sometimes) is "just right", depending on how well I managed to measure the vertical play. MEASURING saves un-mounting/remounting (to shave off "a little bit more")...ie. This stuff is not "fun"...I don't "hate" doing it, but I'm also interested in doing a good job as quickly as possible.
This is what a shaved-down "Miraphone-style" bearing looks like:
Because there's so much circumferential surface area on a TUBA rotor, it's not uncommon to encounter tuba rotors that rattle up-and-down YET aren't really very leaky at all.
There are also "hillbilly" tools that have been devised (sold out of "Elkhorn") to swedge down the openings in rotor casing for rotor stems, (if there's lateral play, there), but often just removing the VERTICAL play (keeping the rotor body all the way "up there" eliminates (sometimes: misdiagnosed) lateral play.
Again...
Your local guy might (possibly/probably) have better ways to remedy this problem...but these are how a dumb southern hick does it.
(I'll wait for some folks to copy/paste some of this, and post "authoritatively" about it on fb...Again...There PROBABLY ARE better ways to accomplish this, but these two ways are how I do it.)
complete "nickel plating" ROTOR rebuilds:
I hate these. I've done a few. (It's trouble for me, because I don't have either copper nor nickel plating tanks here, and I have to send rotors back-and-forth to someone who does). It's difficult to do them with any precision, it's expensive, and it's just so much (yeah...even more expensive but) nicer to replace the complete rotor assemblies (or - when possible - buy nearly-fitting new same-make rotor bodies, and fit them to not-badly-worn casings) - where all surfaces are ACTUALLY PRECISION MACHINED, on a tuba. I NEVER buy (for resale, and certainly not for myself) French horns or tubas that have been through nickel plating ROTARY valve rebuilds. Others' view on this differ greatly from my own.
----------------------------------------
I'm going to go ahead and post how (bloke) removes rotor vertical play.
Those who have better methods may denounce/condemn/laugh.
ok...
When the REMOVABLE rotor bearing has a LIP (which SITS ON the back of the casing), all I do is to grab a saxophone tone hole file (WIDE/EXTRA-FINE "TEETH"), file down the back of the casing (maintaining 100% contact the entire time), and continue to re-try to rotor-and-bearing UNTIL the up-and-down play has been eliminated. I like to file N-S for a bit and then file E-W for a while (or NW-SE / SW-NE...depending on what stuff might be in the way). Changing the direction of the strokes gives me feedback as to whether I'm "digging" in too much on one particular side of the casing opening. Again...It's important to try the rotor/bearing every so often, so as to not take away too much material...but - if slightly too much material is removed - that's not unlike MANY brand-new rotor assemblies, so...
When the REMOVABLE rotor bearing sits down IN the casing on a LEDGE (ex: MIRAPHONE), well...I have to fire up the lathe. I mount the outside center of the removable bearing into the head stock (barely more than "just" tight enough to hold it) and turn down the outside edge of the UNDERSIDE surface (the surface which faces the rotor body) of the bearing. Cutting in only a millimeter (as those ledges are so narrow) is enough, but I might cut in as much as 4mm...[1] carefully "dig in", then [2] pull back to the edge. I BARELY shave them and test them OR (as it's actually possible to measure the up-and-down travel) sometimes I trust the marks on my lathe and shave them down about .001" LESS than the amount that I measure (in vertical play). .001" less (sometimes) is "not quite enough" and (sometimes) is "just right", depending on how well I managed to measure the vertical play. MEASURING saves un-mounting/remounting (to shave off "a little bit more")...ie. This stuff is not "fun"...I don't "hate" doing it, but I'm also interested in doing a good job as quickly as possible.
This is what a shaved-down "Miraphone-style" bearing looks like:
Because there's so much circumferential surface area on a TUBA rotor, it's not uncommon to encounter tuba rotors that rattle up-and-down YET aren't really very leaky at all.
There are also "hillbilly" tools that have been devised (sold out of "Elkhorn") to swedge down the openings in rotor casing for rotor stems, (if there's lateral play, there), but often just removing the VERTICAL play (keeping the rotor body all the way "up there" eliminates (sometimes: misdiagnosed) lateral play.
Again...
Your local guy might (possibly/probably) have better ways to remedy this problem...but these are how a dumb southern hick does it.
(I'll wait for some folks to copy/paste some of this, and post "authoritatively" about it on fb...Again...There PROBABLY ARE better ways to accomplish this, but these two ways are how I do it.)
complete "nickel plating" ROTOR rebuilds:
I hate these. I've done a few. (It's trouble for me, because I don't have either copper nor nickel plating tanks here, and I have to send rotors back-and-forth to someone who does). It's difficult to do them with any precision, it's expensive, and it's just so much (yeah...even more expensive but) nicer to replace the complete rotor assemblies (or - when possible - buy nearly-fitting new same-make rotor bodies, and fit them to not-badly-worn casings) - where all surfaces are ACTUALLY PRECISION MACHINED, on a tuba. I NEVER buy (for resale, and certainly not for myself) French horns or tubas that have been through nickel plating ROTARY valve rebuilds. Others' view on this differ greatly from my own.