vertical damper springs

[Newton Hunt]

Hi David,

An arm from the tool is used to push against the damper felt and
pressure is read.

To weaken push the spring away from the damper lever and to strengthen
pull in the opposite direction after unseating the spring.

Not hard to do, really.

The amount of pressure to use is dependent upon the efficiency of the
dampers, their condition and all that stuff.  Pressure against the
string is a requirement but more pressure will not improve efficiency
of damping appreciably.  So how strong or how weak?

My personal Yamaha, a 1970 P2-F, has damper springs that are strong
enough to effect the touch of a pianist when playing lightly and
causes bobbling hammers.  It took me years to figure out the problem
then I was too old to pull on springs.

What I would do is carefully listen to s bunch of notes then weaken
several springs and listen again for differences then pick a median
pressure and adjust the whole set on a graduated scale, higher in the
bass and lighter in the treble, using a spring loaded pressure gauge. 
Now that my former wife has the piano...

I have never seen any tension specs from anyone although I am sure
there are such in some factories.

One other note, all up and down weights are taken with the dampers off
the action.

		Newton