Richard Vance mentioned the Ampico grand key limiter rails which are
mounted to the underneath side of the whippen flange rail in a grand
action.  Many rebuilders have never seen these because they would have to
take the action stack off the key tray and turn it upside down to look.

This is a very good observation that Richard brings to the discussion,
however, these limiter rails do not enter into the adjustment for the
dampers during soft passages, since they are strictly key overtravel
adjustments, meant to be adjusted to about 1/16" greater travel than the
maximum key depth at the front rail, also called the "aftertouch" of the
key.

If the key overtravel rails were to interfere in any way with the full
key travel, then it would be impossible to regulate the touch.  The hammer
lift rail will never allow the key tail to raise above the resting
position of the damper lever, anyway, which means that the heaviest key
cannot drop more than, say, 1/8" to 3/16" at the front.

However, it is a good idea to be sure that these limiter rails are
secure.  I have never had to use "sandpaper" washers, and I'm sure it IS
an old tuner's trick, as old tuners could get very tricky, particularly
in their old age, but there actually IS another stop for, say, 69 of the
83 playing notes of the Ampico-- that being the damper stop rails, which
must be set at the same distance of overshoot that the key limiter rails
are set at, to prevent the dampers from hopping on strongly played
notes.

Craig Brougher