Step 38, Check gram weight resistance all 88 keys
Step 38 in the 50-point checklist is to use gram
weights to help find too little or too much resistance at the key, something
the pianist will surely complain about if overlooked. Unfortunately, many
technicians do overlook this very important step when regulating an action.
There are two aspects to this step. Through the use of
gram weights one can find problems with the lead weighting of the keys, or more
frequently, one can find problems with the frictional resistance in the action.
Since a fair amount of confusion can result when talking about both aspects, I
will attempt to separate the two.
The weight resistance in a grand action can be defined
as the equation W= (D+U)/2 . Where W is the
weight resistance of the action as felt by a pianist at the key, D is the
downweight pressure of the key measured in grams. The frictional resistance can
be defined as the equation F = (DxU)/2 . Where F is the friction
resistance of the action. How we actually take the down and upweight measurements
will be postponed until later. Right now the important thing is to realize the
difference between the two concepts.
The weight resistance in an action is the result of
the front half of the key having to lift the hammer/shank assembly, the
whippen, and the back half of the key. This of course includes any lead weights
which have been added to the keys. It does not include lifting any part of the
damper assembly. Nor does it include the amount of force needed to push the
action through the escapement. Rather, it is the force needed to push the key
at rest down to the point of escapement. All measurements are taken with the
action in the piano with the dampers blocked up, or with the action out of the
piano on a bench. Once the keys have been weighted at the factory, this weight
resistance is fairly well established for the life of the piano. It does change
a little as the hammers wear and need reshaping, causing them to lose a little
weight. But this slight variance can be reestablished when the hammers are
replaced, assuming the replacement hammers are the same weight as the original.
So, for all practical purposes, if the factory did a good job when the keys
were leaded, the regulating technician should not have to worry about the
weight resistance of the action. In rare cases, the weighting of the keys may
need to be altered slightly. This will be covered later...
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