[pianotech] Worst Bass/Tenor Crossover in Universe

[Encore Pianos]

I have heard that agraffe bridge systems like the Stuart is designed to be
used at "zero bearing" ( I believe that Stuart claims to be such, if I am
not mistaken).  But I have never understood why, if all else about a
soundboard assembly is equal in design and construction, that this would be
the case.  It seems to me like they would have more or less the same
requirements of bearing and crown to drive the board. 

Indeed, the 7' 6" Steingraeber Phoenix that I saw at Larry Buck's shop in
Lowell, Massachuesetts last May appeared to be ribbed "normally" in width
and height and number, although I did not take any measurements to verify
this.  Additionally, there was an adjustable vertical hitch pin of Richard
Dain's design, which would suggest that careful setting of downbearing was
considered important (again, I took no measurements to verify this).  The
Dain agraffe used by Steingraeber is very similar in design to the Stuart.  

Del, I would be grateful if you could explain why the loading requirements
for an agraffe bridge system would be different from a traditional bridge
with pins and side bearing, if that is the case.

Will Truitt



-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Delwin D Fandrich
Sent: Tuesday, January 08, 2013 2:04 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] Worst Bass/Tenor Crossover in Universe

1)  The only place where panel cracks are a concern are in those limited
areas where the grain angle of the panel roughly parallels the inner rim. In
most pianos this condition is only found on the inside curve of rim on the
treble side. And sometimes along a soundboard cutoff bar. Other than these
two areas there is no need to set the ends of the ribs into rim notches
unless your intent is to stiffen the assembly. 

2)  No bridge termination system is "designed to be used at zero bearing."
The termination system doesn't really care whether there is string bearing
or not. String bearing has to do with the physical interaction between the
vibrating strings and the resulting motion of the soundboard assembly. 

Cantilevered bass bridges have long been set up with "zero bearing." Fifty
years ago old-timers were warning us young whipper-snappers of the dangers
of putting any string bearing on cantilevered bass bridges. Even if you were
to load up a cantilevered bass bridge with a bunch of string bearing it
wouldn't last long; the thing just rotates and the soundboard assembly just
distorts and it all goes away.

Delwin D Fandrich
Piano Design & Fabrication
6939 Foothill Court SW, Olympia, Washington 98512 USA Phone  360.515.0119 —
Cell  360.388.6525 del at fandrichpiano.com — ddfandrich at gmail.com


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Jim Ialeggio
Sent: Tuesday, January 08, 2013 9:56 AM
To: pianotech at ptg.org
Subject: [pianotech] Worst Bass/Tenor Crossover in Universe


... I am also edging closer to selectively bagging rim notches in cross
grain areas where stiffness is required(ribs), but freedom of movement is
desirable. (but still a bit concerned about panel cracks at the rim
joint)

Also, there might be a completely different approach. Since the Phoenix
agraffes are designed to be used at zero bearing, the zero bearing could
conceivably allow a high bass cantilever without the roll
tendency???maybe??? Though in a sh-t box like Terry's victim, the point is
largely hypothetical.

Jim Ialeggio