Bill Freeman wrote:

If the bolt problem is guitar string type of vibrations (lateral vibrations), then
providing an elastomeric doughnut (sleeve, tube, whatever) in the middle which is
snug on the bolt and in the hole will dramatically detune the system and provide
substantial damping.  Both are good.

If the bolt hole size is consistent, I'd use a sleeve in the middle portion. Sounds
like what the 20B has.  It needs to be a snug fit in the hole, does not need to
cover the whole bolt, does need to be in the middle, at least approximately.

Actually, from a purely off-the-cuff harmonics point of view, the damper should *not*
be *exactly* in the center.  Near, but slightly off, center is optimal; it forces the
vibrating object (bolt shaft in this case) to seek out much higher order harmonics,
which have proportionately lower energy.

Russell Kent

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