Virtual Ribs, A new crown support method

[Thomas Cole]

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Adjustability comes to mind. You can come only so close to the optimum 
amount of stiffness in the different areas of the board when choosing 
panel and rib materials and dimensions, and that stiffness may change as 
the panel ages. So magnets would allow for a fine tuning, no?

Tom Cole

David Love wrote:

> Why would this be better than simply creating a rib crowned and 
> supported panel that can be compressed to the requisite stiffness 
> through the use of downbearing without overstressing the panel?
>
>  
>
> David Love
> davidlovepianos@comcast.net
>
> -----Original Message-----
> From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On 
> Behalf Of Erwinspiano@aol.com
> Sent: Monday, April 11, 2005 6:34 PM
> To: pianotech@ptg.org
> Subject: Re: Virtual Ribs, A new crown support method
>
>  
>
>   RIc
>
>   May the force? be with you brother.grin
>
>   Dale
>
>     Hi folks
>
>     After a few months of experimenting, I am ready to announce a new (I
>     believe)  method of supporting crown for any type of soundboard. The
>     method allows for both restoring crown and supporting it in older
>     panels, and designing new panels in which the concerns of mass levels
>     and degree of assembly stiffness can be to a far greater degree
>     treated
>     independantly.
>
>     In essence, an array of repelling high power neodym magnets of
>     appropriate dimmensions and strengths are used to support crown
>     against
>     downbearing from the strings. One set are imbeded in soundboard
>     button
>     similar wooden sheaths and are attached to the soundboard with
>     glue and
>     screws.  Opposing these is another set which are mounted into a very
>     strong wooden beam such that their distance from the soundboard
>     attached
>     magnets can be adjusted easily from below.  One can either choose to
>     simply provide support directly under the bridge, or without too much
>     difficulty, contrive what amounts to a system of virtual ribs with
>     fully
>     adjustable support for crown.
>
>     For edification... Neodym magnets that measure 30 mm Ø by 5 mm
>     thick can
>     hold / push approximately 25 kilos.  Since there is no phsyical
>     connection between the soundboard and opposing magnets, the
>     assembly is
>     not directly mass loaded. Hence stiffness and crown support is
>     provided
>     without mass loading.
>
>     More later on as I formalize an article on a working example I am
>     hoping
>     to finish soon.
>
>     As is my habit... this is an open source idea, I encourage any and
>     all
>     to take up and refine it in their own fashion.  My own initial
>     results
>     indicate that the principle is very successful.
>
>     Cheers
>     Richard Brekne
>
>  
>

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