touch weight

[Newton Hunt]

> I have been unable to find anything ready-made,

Strain guages are common.  What I think would be uncommon is the
calibration circuity.  You will be measureing stress downward, unlike
a scale which measures upward.

WIth a strain guage the static friction could be subratcted from the
sliding friciton by removing the highest measurements of the key
stroke.  Average the remainder should give a good weight measure.  The
reverse of the key mover when the weight increases when let-off is
reached and measureing the reduced weight will give a good up weight.

Would measuring the weights at three or for velocities give an idea of
inertia?  Inertia is a major consideration of drive head arms so you
may have some information or ideas in this area already.

A rail suspended over the keys high enough to allow free access to the
keys would be good with a piston that comes down to work the key but
will clear the sharps when it is moved back to do the sharps.  Touch
weights are done on a bench so a simple frame would be easiest.

The current practice is to remove the front most key weight then place
a 20 gram weight on the key then set the down weight by moving weights
back and forth on the key then using differing weights determining how
much weight the key will lift, this gives the friction of the key. 
Then use a set of up and down weights predetermined by friction and
desired balance weight and cut a weight down until it will achieve the
goal by placing it into the vacated hole.

A thumper would not be needful is you could provide such a machine at
a reasonable cost.  Of course we still would need a digital scale for
doing hammer weights.  Of course now we use a scale to weight each key
front then do the final balance weighing by adjusting the wippen
spring tensions.

Tell me more of what you think.

		Newton