pianotech-digest V1997 #1919 (long)

[Roger Jolly]

Hi Ron,
           Your thoughts are correct. Because of the additives, V Pro is
not Grey Cast Iron but an iron alloy. the additives are for two or three
reasons. 1. so the melt will flow rapidly without pockets. 2. controls the
size and amount of free carbon crystals. 3. The alloy will not crack and
distort with the rapid cooling.

True grey cast iron with the wet sand pour system. When the melt hits the
wet sand the skin of the cast is case hardened. and heat is applied as soon
as the the  cast is complete.
The best plates I believe are cooled over a 24hr period to reduce internal
stresses within the plate. This prevents the plate from becoming too
brittle. this evidenced by the flexibility of the plate when stringing.

Like you I feel unless  you had 6 pianos  will the same scaling 3 with each
type of plate. we are only guessing at the results. It seems to me that V
Pro struts and plate thickness is greater that comparable grey cast.  Is it
not as strong under compression?  the full perimeter design that is in
favour with vertical V Pro plates tends to make me think so.

More mud to cloud the waters. smile!!???
Roger
>
>* This is exactly contrary to what folks have been saying on this list. I
>don't recall anyone claiming anything but softer iron in the V-Pro plates,
>with a harder iron, and a sort of case hardening in the sand cast. Is that
>right, or am I in the Twilight Zone? If I read the posts right, who's
>correct, Ed, or the people with contentions contrary to his? Which is it, is
>the V-Pro plate harder, or softer than traditional sand cast plates, and by
>who's authority is this determined? Also, I got into a discussion recently
>where (nearly) everyone and his brother claimed that the V-bar needed to be
>hard, *and* of a small radius profile in order to minimize string noises in
>the front duplex, in some cases, regardless of the counter bearing angle and
>length of the duplex segment. This is, again, at least partially contrary to
>what Ed wrote. Again, who's right, and by what authority? Also, how does a
>larger capo radius accelerate capo wear by not allowing the string to have a
>precise pivot? That doesn't make any sense to me at all and I'd like it
>explained. How can a longer support area for a given load, on a given
>footprint width, result in accelerated wear of the support? This is contrary
>to logic as I know it. How does this work? Let's backtrack and plug a few
>holes before we hotly dispute anything else, what do you say?  
>
> Ron N
> 
Roger Jolly
Baldwin Yamaha Piano Centre
Saskatoon and Regina
Saskatchewan, Canada.
306-665-0213
Fax 652-0505