Touchweight and more toughweight

Newton Hunt nhunt@jagat.com
Sun Sep 20 21:50 MDT 1998


Ok, I'll bite on this one.

First we need to consider one element that has not been discussed yet;
inertia.

Inertia is the energy required to get an object moving.  In our corral
this refers to how much weight is in the keys.

This then begs the question of efficiency, friction and hammer mass and
leverages.  Since an action is a series of levers arranged to help make
sound all these issues have to be considered.

Turn of the century pianos, and earlier ones, were essentially designed
to accommodate smaller concert halls than the ones we have now.  In
order to fill the hall with sound the hammers have to be heavy to
produce that much sound.  Heavy hammers, increased mass, requires that
there be more mass in the fronts of the keys to compensate.

Steinway's "accelerated action" was nothing more than the use of the
"moment of inertia" which in physics dictates that the weights start at
the center or balance point to promote rapid return: faster repetition.
At the expense of the pianists energy input.

Many of the European pianos, and some Asian ones, have incorporated
wippen helper springs in their actions, in part to help compensate for
heavy hammers.  The more crudely designed and executed actions will need
more help than others, but nonetheless it is becoming abundantly clear
that to help compensate for increased mass of the hammers and the keys
the springs will help immensely.

The helper spring adjustments have been gone about in the wrong way.
Normal practice is to adjust key weight after the springs have been
hooked up.  A better practice is to weigh out the keys THEN hook up the
springs and adjust the spring tension to adjust final touch weight.
This will give the most even action.

Touch weights should be measured in terms of their BALANCE WEIGHT, that
is the average of the up and down weight.

Below a certain balance weight the action will falter.  This limit is
somewhere around 32 grams.  Old Steinway concert grand specs called for
a 35 gram bw.  Many professionals will find this a little light for
stage work.

38 grams of bw is what I used in teaching studios and practice rooms.  I
have gone as high as 40 grams bw but would consider anything over that
over weight and a potential hazard to young players.

Leverages can help or hinder bw.  Moving knuckles is a good start
point.  Using several hammer shanks with knuckles of different size and
locations will help determine which set would provide the best results.
Relocating knuckles seems a little radical to me.  I would rather change
the shanks

Capstan relocation is the next area for improvement.  I have written
earlier of Steinway's practice of locating capstans more indirectly than
others which does lead to dislocations.  Moving them more than 3mm will
involve relocating the cushion.  Something that David Stanwood does
often, but cutting and regluing requires good jigs.

Installing helper springs is also a very hands on process.  David has
worked out procedures for making it easy, but it is costly.

Changing the spread action is something that can be done.  On a Steinway
I would shim a flange out to determine the effect, measuring up and down
weight at every step.  The closer the two come the better.  You can take
and make a special flange by cutting off the scallop and thinning down
the remainder of the flange so the center pin can be moved closer to the
rail.  FInding the optimum spread action can be found this way and then
the rail can be resoldered or flanges can be shimmed.

A certain amount of mass is desirable.  How much is a matter of choices,
money, time and available technology.  Removing excess lead is the
objective in most cases.  You are limited by the weight of the hammers
themselves.

A certain amount of friction is also desirable; to eliminate it entirely
is not desirable.

If you understand action ratios, masses and leverages an action can be
made to perform extremely well indeed.

THis little piece should raise more questions and other comments, which
is it's intent.

                            Newton









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