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Yamaha covered their springs in some sort of soft plastic, but as valve oil made that cover come loose, I prefer the Boosey & Hawkes approach of spring dampers: soft plastic washers at both end of the springs.

Klaus

There are some very strange dynamics going on with the very nature of a coil spring. Try to imagine the diameter of a spring getting a TINY bit larger as the spring is compressed and then moving back to it's original diameter when it's released. The ends of the spring move a tiny bit and actually 'scuff' in the spring pockets. Besson tried to address this with rubber pads. Yamaha addressed this by coating the ends of their springs with plastic. King has never done anything about it. In order for a spring to do it's job, it has to 'scoot' a tiny bit in either the bottom of the piston or in the bottom cap. A little oil helped that situation out a bit. I like to apply a small dab of synthetic grease inside the bottom cap to do two things.... 1) to keep the caps from becoming stuck. and 2) to provide lubrication for the spring.

I've heard other repairmen pooh pooh the notion of springs increasing in diameter as they are compressed. But.... I spent 25 years in the tool and die industry and can tell you first-hand that I've seen the bottoms of spring pockets literally eaten away by exactly what I'm speaking of. Of course, those die springs are MUCH heavier. But... the same dynamics apply.

I've thought many times of working on a 'spring-less' system to return pistons. One of these days I'll get around to building a prototype.

TubaTinker wrote: I've thought many times of working on a 'spring-less' system to return pistons. One of these days I'll get around to building a prototype.

On a top action horn, bungee cords connected to the top bow? Then if your fingers can't get in there, some sort of rod coming out the bottom of the valve with a finger hole.
Maybe?

TubaTinker wrote:There are some very strange dynamics going on with the very nature of a coil spring. ...

But.... I spent 25 years in the tool and die industry and can tell you first-hand that I've seen the bottoms of spring pockets literally eaten away by exactly what I'm speaking of. Of course, those die springs are MUCH heavier. But... the same dynamics apply.

Terrific and informative post. Thanks.