Two action questions

[Newton Hunt]

>  (they are heavily front leaded) 

This is the clue I was looking for.  Three, at most four, weights in
the bass is enough for a properly set up action.  If this action has
wippen helper springs with a lot of weights in the keys then you have
a major geometry problem.

Take a spare wippen flange and cut it so the center pin will move
closer to the front of the keys.  This will allow you to evaluate the
best possible action spread, shorter to longer than current setting,
without moving the rails, by shimming the flanges.  Once this is
determined you can move the rails.  Reevaluate at the new settings. 

The smallest difference between up and down weight is the proper
spread between hammer center pin and wippen center.  Too long and the
difference increases, too short and the difference increases.

There are three other possible problems.

1.  The action stack is too low or too high or too low or too high in
the front or the back.  If this is a piano still in production you can
get the specifications for the height of the hammer and wippen center
pins from the keybed.  The blocks of wood under the feet of the stack
are cut by the action installer.  There could have been an error
here.  Depress a key half way down and run a straight edge from wippen
center pin to the center of the key pivot point.  If the capstan does
not meet the wippen heel on this line then you may consider this a
source of the problem.

2.  Capstan location is super critical to proper action functioning
(plus or minus 1 mm is substantial).  If it is too far back (likely on
this action) the touch weight will be too heavy because the action is
under leveraged.  If the capstan is too far forward the action will be
too light for proper functioning.  This is determined by weighing the
hammer from center pin to strike point, weighing the wippen from
center pin to capstan contact point, weighing the key from center of
the pivot point to within 1 cm of the front of the key,  Weighing to
determine the EXACT key ration.  Using these numbers and the up and
down weight the exact action ratio can be calculated.  5.5 is
considered to be the major reference or objective point, anything
under this is under leveraged, any thing over this is considered over
leveraged; tolerance from action to action is minus .5 and plus .8. 
If this is a major cause then relocating the capstans is the best
solution.  You will need a digital scale that reads to .1 mm, least
frition possible resting points for the parts and the proper
procedures from David Stanwood at Stanwood@tiac.net.

3.  Hammer bore distance can also cause geometry problems.  If the
bore is too long or too short then you will get the jack alignment
problem.  Measure from the underside of the strings to the keybed
(beginning and end of each section), measure the height of the hammer
center pin from the keybed at each end of the action.  Subtract the
smaller from the larger and you have the proper bore distance for the
hammers.  Measure from the strike point to the center of the hammer
shank.  Correcting the bore with a new set of hammers will solve this
problem.  Anything different form plus 1 mm is a problem.

A whole series of errors on the production line can cause a chain of
small errors which cumulatively cause a major problem, so any
combination of the above can be the problem.

Analysis, evaluation and planning are required to solve these types of
problems.

Lots of luck.

		Newton