[CAUT] stack fit to keyframe

[Bob Hohf]

Fred makes an important point that, friction increase or not, there may be
some other bad effect to deviating from the line.  However, what we're
talking about is what to do if the existing string height doesn't allow
optimum configuration of the action parts.  The most common scenerio I've
seen is string height too high.

If you maintain the optimum line in this case several things may result:

1.  Hammershank swings above parallel to keybed
2.  Hammer overcenters at strike
3. Hammershank so high above (nonadjustable) rest felt that the action locks
up on certain blows
4. Jack may jam into felt at the back of the rep window
5. Loss of mechanical efficiency

Or you can raise the stack, sacrificing the line and:

1. The wippen cushion wears out faster.

This is the sort of real life choice that we have to make all the time in
action work.  What would you do?

Bob Hohf


  While the friction created by deviation from the line (point of
convergence of the arcs) may not be measurable, it may still be significant
over time in the wear created on the felt, leading to accelerated "lowering
of the hammer line" and to more friction down the line when the felt becomes
more cupped.
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