Pianotech

As a tech and a rebuilder there is an idea that has been brewing in my thinking that goes like this:

• String tension, being lower than and misaligned with grand plate struts, creates an upward stress vector along the length of the plate struts.
•  The back beams and the rim resist rotational forces of distortion generated - again - by string tension, as that tension generates downbearing and torsion on the soundboard.
• The very same string tension generates upward force on the plate struts and downward force on the back beams as they resist an inward folding rim rotation.
• The place where these forces are directly connected is the nosebolts.
• therefore, if nosebolts are set to neutral (perfect bedding of an untensioned system), then the plate and the beams will be permitted maximum flexibility.
• If the nosebolts are raised (for example, to reduce downbearing), then expanding pressure is being added to a system, pushing more stress into the plate and increasing the rotational distortion already underway in the rim from board forces.
• on the other hand, if the nosebolts are set 1 mm lower than the plate, introducing tension preload between the plate struts and the back beams, here's what happens: the strength of the struts and the backbeams under tension both fight the upward force of the strings trying to bow the plate struts upward. And at the same time, slight torsion is introduced to the rim.
• A hypotheses here could be that setting nosebolts just slightly low as a preset, could "tighten" this "dynamic tension loop" and generate a more powerful tone as well as sustain.
• Overdoing it however could be unwise except in a scenario of experimentation to measure changes. I have not taken on an extreme experimentation as of yet.
• Lastly: looking at grand piano plate struts I've often marveled at the compressive load they can handle since their beam structure lies above the string tension line particularly across the long bridge. Harnessing the rim and beam structure more fully by pulling these two above-and-below structures together into a healthy tension seems to be not only an interesting idea but safer for the plate struts than a neutral beginning setting. On the other hand, when you consider how much the plate struts want to snap upwards under load, you start to recognize how truly unsafe it is to ever raise nosebolts to induce upward pressure where a strut lands into a plate deck. Especially on a strung piano but also as a preset. Once a rebuild is completely finished and I'm voicing, I know whether a piano is singing with the power and sustain I crave - or is struggling. These are the things I consider since after hundreds of hours rebuilding a piano - I personally as a pianist want to find a beautiful and magical instrument to hand over to a customer.

I hope someone finds this of interest. Cheers.