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so, I just got the rubber and am waiting on the cork. I installed one bumper so far. It SUCKED to get in. I settled on tweezers and a prayer to get it in the slot. I am wondering what your tricks are.(If there are any, of course). I am replacing the corks also when I get them. Any tricks for those. FWIW I am replacing the bumpers on a Miraphone 188 that I've ad MAYBE 2 months. The 1st valve and 3rd valve corks are decimated and the 1st valve rubber bumper was splayed in half (that is the one I just finished)
Thank You very much!

I think the easiest way to replace bumpers is to remove the screw that holds the stop arm on and take the two screws out of the bumper plate. Then... take the bumper plate off and put it in a vice with the bumper slots up. Then... it's a pretty simple matter to use a blunt screwdriver to force the rubber or cork into the slots. Then you can trim both sides flush with a razor blade. Once you've got those new bumpers in place and everything put back together, you need to unscrew the rear caps and have a peek at the alignment marks on the rotor bearing spindle. IF the alignment mark on the edge of the rear bearing plate is in alignment with the mark on the rotor housing AND the marks on the rotor spindle line up in both the forward and back position, you're done. If the marks don't line up, you either need to use a thicker bumper or shave the exposed part of the bumper. I usually use an Xacto knife to trim the bumpers.

I've been known to replace just one bumper while the plate is on the horn, but it's almost always easier to just take the plates off the horn.

While you're going through the motions of taking those plates off and putting them back on, you can make sure they are tight, too. The screws should be reasonably tight but be careful not to overtighten them to the breaking point. Loose bumper plates and loose screws in stop arms are among the biggest sources of rotor noise.

NOTE: If the stop arm is too tight on the rotor stem to be removed with light pressure, DO NOT attempt to pry it off with a screwdriver. This can bend the rotor stem or even break it off. Two wedges inserted between the stop arm and the front bearing 180 degrees apart and a couple of light taps should get it off. If all else fails, take it to an instrument repairman. Don't force anything!

This is not an answer to your bumper replacing problem, but...

Why do these stops shred up so quickly? My school got 2 new 186's a year ago; I used on and my section mate used the other. We started using them at the exact same time, but a couple of months later, his rubber stops were all cut up and the cork stops soon suffered the same fate. His were all shredded, but mine were perfectly fine.

What's up with that?

As a beginner and seldom contributor on the board, I would like to say how much I appreciate the wealth of knowledge shared on the board. I have learned very much from everyone's comments.

Bumpers: I had my cork bumpers replaced on my year and a half old Miraphone 186 and was quite
surprised at the changes in the horn. The repairman talked about the regulation marks and showed how they lined up properly with
the new corks, the playing difference was immediately noticeable in the horn being freer (is that a word) or less "stuffy" to blow.

2 Questions: Where could you purchase new cork and rubber bumpers?
And: are there any books on brass instrument repair available?

Thanks for any replys,

Bill

Bill, I know there is at least 1 book on brass instrument repair. I saw it in my band director's office, but I didn't catch a title.

When my section mate's horn began to really be weird in playing from the shredded bumpers, he took a couple of hours in the office with a blank sheet ( ) of the rubber material and cut the bumpers out with a knife. They fit in, and I guess they work well because he didn't have any problems afterwards.

Note that he just used rubber to fashion the new stops and replaced all (including cork) the original stops.

No, we don't. I've only oiled the valves once in the year I've had it, though.

FWIW, I don't like using cork for my bumpers. I find that it doesn't last very long at all, and the hard black rubber stopper material seems darn near indestructable. I trim down the rubber with an exacto knife and use a pair of needle-nose pliers to get the stops in place. Then I trim the rubber as necessary where it meets the stopper arm to get the valve alignment right. When in doubt, take it to a good repairman.