Cutting Frames

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Hi list,
I recently decided to some experimentation with an old upright I have.
It is a Victor-Paling  circa 1920s?? no numbers
assembled here in Aus (I think) but made in the
USA. I wanted to see what would happen if  the frame strut in the
upper treble area between notes 66 and 67 was missing.It is a normal
overstrung upright frame with the one break in the treble between 66
and 67.
I let down all the tension then proceeded to cut through the strut
with my trusty angle grinder.Interestingly when there was only 10mm of
the cut to go the frame made a small bang and cracked through the last
section of the cut. So the frame either wasn't fitted properly and was
under some tension or there was some internal tension from the casting
process . After I had finished and got my hearing back again!,I
measured the cut which was 4mm, the pinblock is coming away from the
back of the piano slightly by about 2mm in the middle tapering off to =
nothing at
the ends, it was like this from the before I started.
I then chipped it back up to tension a couple of times while holding
my breath and closing my eyes waiting for a piece of cast iron to come
flying out. The action is totally stuffed at this stage so I can't
tune it but I think 95% of the tension is back on the piano.
As I was increasing the tension I noticed the gap of the cut was
getting smaller, by the time I had finished , the gap had decreased to
1.5mm. I measured the pinblock again the gap was still the same.I
checked the rest of the frame there seems to be no signs of fatigue,
the strut that I cut has moved slightly towards the bass but only by
about  .5mm not much at all.

My questions to the list=20
Is how did the gap close up ?
 where is the frame moving?
the bottom half or the top half.......
Will tuning stability and tone be affected?Dramatically

Thanks ,

Stuart Balsillie
Piano Technician
Woodend, Victoria
AUSTRALIA
piano@iaa.com.au



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