[pianotech] Reversing Crown

Noah Frere noahfrere at gmail.com
Wed Dec 30 22:14:27 MST 2009


Sounds good. I don't understand this though: "that means that the bridge is
being *pulled up* by the strings" in the second case. It was my
understanding that negative bearing means the bridge is lower than it should
be, causing the strings to be slightly v-shaped rather than ^-shaped.

On Thu, Dec 24, 2009 at 11:39 AM, David Love <davidlovepianos at comcast.net>wrote:

>  If you have positive bearing and positive crown then you have downward
> pressure on the board with residual crown so if you take off the strings the
> board must rise, i.e. the crown remains positive.  Good sign.
>
>
>
> If you have positive crown with negative bearing that means that the bridge
> is being pulled up by the strings and to what degree that is responsible for
> the crown formation you can’t tell until you take off the strings.   Bad
> sign.
>
>
>
> If you have positive bearing with negative crown you can’t tell whether
> when you remove the strings the board will rise to show positive crown or
> not since you don’t know how the bearing was originally set or exactly how
> far down the bearing is pushing the crown.   Bad sign.
>
>
>
> If you have negative bearing and negative crown that means the board is
> being pulled up but even with that is not achieving positive crown.
>   Definite burnt toast.
>
>
>
> Keep in mind that each section of the piano may show different
> relationships to crown and bearing and, as Ron mentioned, several
> measurements are necessary across the panel.
>
>
>
> David Love
>
> www.davidlovepianos.com
>
>
>
>
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