Adjusting wippen assist springs

[Overs Pianos]

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Sarah,

Thanks for an interesting post. This debate re the merits or 
otherwise of assist springs refuses to go away.

Only yesterday, while debating how our piano no. 4 was going to be 
weighed off, I gave in to pressure and agreed that our piano no. 4 
could be set up without any assist springs However, in an effort to 
get somewhere on this debate, piano no. 5 will be set up with spring 
assistance. Both pianos will be otherwise identical regarding their 
actions and key boards, and both will be used together on occasions 
for two piano works at the Sydney Conservatorium.

A couple of days ago Phil Ford asked for ideas regarding the set up 
of assist springs. We set assist springs with a tapering of 
assistance from stronger in the base to weaker in the treble. After 
minimising the friction and mass variations of the components (the 
hammer weights will, of course, conform to a curve), with the springs 
disconnected, the DW is adjusted using lead weights -  to a curve 
which is heavier than the final setting we require. This weight curve 
is corrected by connecting the springs and adjusting their tension to 
bring the DW to the final figure.

As an example, after deciding on, and building into the action and 
keyboard assembly the desired hammer/key ratio, we might decide that 
we want the assist spring to lighten the DW by 8 grams for a final DW 
of 52 grams on note A1. Therefore, we would set the DW at 60 gr with 
the assist spring disconnected, then after reconnecting the spring, 
adjust the DW to 52 gr. The whole keyboard can be set up in this 
manner quite efficiently when the assist springs have adjusting 
screws. I believe that assist springs should not be used unless they 
are accompanied by adjusting screws. The idea of adjusting assist 
springs to fine tolerances without adjusting screws, seems to me, to 
be simply impractical.

Best,
Ron O.

At 12:12 PM -0500 12/12/03, Sarah Fox wrote:
>
>Hi Ric,
>
>You wrote:
>
>>  The leads output more force then it
>>  takes to accelerate them in all cases because they are (as seen by the
>finger)
>>  on a second class lever
>
>Ah, but with very forceful playing, the keystick accelerates very quickly,
>and the downward force exerted by gravitational acceleration on the key
>leads pales by comparison to the upwards force of the keystick/leading
>against the finger (in direct opposition to the downward force that is
>accelerating it).  The greater the inertia, the greater this force.  Case in
>point: place a 1 kg mass on each side of the balance rail.  Adjust BW to
>something very reasonable.  Now pound the key and try to produce your
>loudest fff.  If you're a really strong pianist with really heavy arms and
>beefy fingers, you might be able to produce an mp.  Why the difficulty?
>It's because the "oppositional force" of the key inertia is far greater than
>the small amount of assistance the key leading might give you (with regard
>to touch weighting).
>
>How do key leads and wip springs change in downward force at different
>levels of play?  They don't.  Gravitational force on the keyleads is
>constant.  Spring force is also constant (for a given position in the
>stroke).  The only difference is that springs can move very rapidly, owing
>to their very low inertia, and lead weights can't.  So with rapid key
>acceleration, the leads fight back, while the springs don't.
>
>As I've suggested to you before, there's another experiment that provides a
>better feel for the real-world consequences of key inertia:  Bundle up 3 or
>4 nickels (15 or 20 g mass) in some tape and suspend the tape by a string
>between the thumb and third finger.  Now "trill" the nickels like two piano
>keys.  This isn't a lot of mass, and yet the force necessary to accelerate
>it would be a significant component of total force on the key.  I accept
>that the hammer accounts for most of the total inertia, but there's still
>considerable inertia in the keystick.  Hammer inertia is fine, as the
>hammer's kinetic energy is delivered into the string.  Keystick inertia is
>not fine, as the keystick's kinetic energy is only delivered into the front
>rail.  IMO, the only function of keystick inertia is to make the piano feel
>"familiar" to pianists who are trained on pianos with lots of keystick
>inertia.  However, I doubt it results in a better instrument, and I would
>expect that the instrument will ultimately evolve to a lower keystick
>inertia and a heavier hammer.
>
>As you suggest, it would be interesting to tease out the relative
>contributions of these different components!
>
>Peace,
>Sarah
>
>_______________________________________________
>pianotech list info: https://www.moypiano.com/resources/#archives


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OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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