laminated ribs

[Joe And Penny Goss]

Ric, If you can stand ON your work, it should hold up <G>
Joe Goss RPT
Mother Goose Tools
imatunr@srvinet.com
www.mothergoosetools.com
----- Original Message ----- 
From: "Ric Brekne" <ricbrek@broadpark.no>
To: "pianotech" <pianotech@ptg.org>
Sent: Sunday, February 19, 2006 12:36 PM
Subject: laminated ribs


> Given the fact that I am about to sink my feet into this kind of thing
> seriously for the first time... I shore nuf would like to see some
> semblance of consensus formed here.  Strikes me that a range of 200 to
> 900 lbs of downbearing on the soundboard is a rather huge window.
>
> Could you guys please go a bit into how each of you arrive at your
> figures ?  And I would also like some words on how typically this load
> is spread over the panel.... along with a few words about how one
> designs ribs to carry the load as it varries over the board.
>
> Also... assuming the greatest load is up in the treble (which I seem to
> have got into my head is the case) how likely is it that given a board
> with grain going perpendicular to the bridge with the longest ribs then
> being in the treble area, would be able to hold up against the minimum
> figure arrived at above.
>
> Thanks
> RicB
>
>
>
> ------------------
>
>
> Dale wrote
>  >/ Ok Now I,lm confused. If were only trying to support only 400 to 600
> />/ lbs. of down bearing force as Del inferred recently or whatever one
> />/ calculates this to be, then what's all the fuss about.
> /
> My loading of new boards these days is typically half again
> over 600 lbs.
>
>
> Ron, so you are saying a 900 lb bearing load is probably an in the ball
park
> average plus or minus for various sizes of pianos & string scale tensions.
> Then my comment a couple weeks ago about bearing being 1000 lbs or more
> depending on who you ask wasn't that far off this figure even though Del
> disagreed with that as being "excessive."
>
>
>
>
> Consider a basic scale of moderately high tension. Say 40,000 lbs.
> overall. With
> this string tension 1,000 lbs of string downforce equals 2.5% of scale
> tension.
> That is quite a lot considering that most companies are claiming string
> downforce more on the order of 0.5% to 1.5% of string tension (which
> would be
> 200 to 600 lbs). I thought I was setting my initial string downforce
> pretty high
> at around 1.0 to 1.5%. I don't like thinking about what I'd be doing to
> a board
> loading it up to 2.5%. I can't imagine it being happy enough at that
> level to
> want to stay there.
>
> Del
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