Frame Cracked Twice, Engineering help?

[Vince Mrykalo]

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Actually, there is a piano technician/welder in our area (Ogden, Utah) that
has
welded literally 100's of plates without a failure.  His name is Wilford
Young.  The secret to a succesful weld in cast iron, isto go slow.  IOW, dress
the crack (vee-shaped), and weld only an inch at a time, let it cool down,
then
go for another inch, etc. until it's done.
I don't think the plate/bolt idea will work.  Reweld.

At 07:34 AM 3/21/00 -0500, you wrote:
>OK, Guys, I need help
>
>Hazleton Bros. 5'10"  Grand.  Neatly rebuilt, (by me).  Too little
>downbearing in the treble, so I lowered it a bit.  (I've Done such things
>before.)  Brought up the tension nice and evenly, installed dampers,
>sounding good at A-440, ready for fine tuning.  
>
>During the Fine Tuning:   THWUNK !!  I couldn't see anything, so I played
>a chromatic scale.  It climbed nicely until I passed the last strut, and
>dropped a fourth.  Then I could see the crack, travelling toward the
>Northeast, but holding near the edge of a circular sound hole.  I QUICKLY
>dropped tension on that section, and then dropped the rest of the piano.
>
>Fortunately this pinblock is only attached to the frame, and not to the
>case, so I loosed everything, pulled out the frame with the block and
>strings intact, and called a welder who assured me he could handle this. 
>
>Re-painted, reinstalled, strings back in place, tension up to A-440 and
>holding.   Last Friday before bed I played a chromatic scale again, and
>it wasn't chromatic. . . . . .  So I dropped the tension on the last
>section and went to bed.
>
>There's more to welding cast iron then I knew.  My welder did not heat
>the plate, nor cool it slowly, as I hear is necessary.  And I've heard
>from a far more skilled fellow, that this kind of welding is very much an
>art.
>
>Question:  What if I had a steel plate created, and with PC-7 between it
>and the underside of the frame to give it strong frictional contact,
>drilled, tapped and bolted  this plate in place below the cracked area. 
>It would be out of sight, and providing considerable strength for that
>area.  Would this be sufficient to bear the tension and give us our whole
>piano back?
>
>Roger C. Hayden, RPT
>Clarks Summit, PA
>________________________________________________________________
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> 
Vinny
Institute Committee member, PTG
<mailto:vince@byu.edu>


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