Open face vs. closed face pin blocks

[Delwin D Fandrich]

----- Original Message -----
From: <larudee@pacbell.net>
To: <pianotech@ptg.org>
Sent: August 13, 2001 7:28 AM
Subject: Open face vs. closed face pin blocks


> List,
>
> Does anyone have any ideas about why so few manufacturers use open face
pin
> blocks?  Cost is a major factor, of course.  Leo Duricic of Bechstein says
that it
> takes a master craftsman 11 hours to fit a block in an open face plate vs.
3 for
> the closed face.  However, precision robotic manufacturing techniques such
as
> those used by Yamaha and others should be capable of greatly narrowing
that
> difference.

The Bechstein design--while beautiful to look at--is a particularly
complicated one to fit. Nor is there is any performance benefit to such
complexity. Many others such as the Bosendorfer designs and the early
Chickering designs are equally difficult to fit. Others were relatively
simple and worked just as well. Open face blocks can be designed such that
they are very little more time-consuming to fit than their closed-face
counterparts. And three hours to fit a production, closed-face block--even
doing it all by hand--is excessive and an indication of poor--or perhaps I
should say, inefficient--design. With some minimal effort spent on the plate
and block at the drawing board it should be possible to come up with a
design and a process that takes no more than 30 to 45 minutes by even the
most methodical of workers. Even less if some of that work can be done by
machine.



> Leo also says that the closed type produces more power, which is why their
> concert size instruments recently switched to that design.  I don't buy
that.
> Bechstein invariably uses agraffes in the entire scale with open face
blocks but is
> now using a capo bar with the closed blocks in their concert instruments.
> I think that this a more likely factor in power production.  Bosendorfer,
which pairs
> open face blocks with a capo bar, agrees.

I don't buy it either. In fact, I'm beginning to question just how much
power is lost in the all-agraffe design. I know it is some measurable
amount--I've studied the charts and graphs--but I'm wondering if it really
an audible amount if all other factors are equal. (I've recently had
experience with a couple of all-agraffe designs that were quite outstanding
all the way to the top--and that with un-lacquered Ronsen hammers. Certainly
there is as much power up there as in many capo d'astro designs.) There are
quite a few areas in which power is lost--or retained--but I doubt the
open-faced pinblock design is one of them. Someone's going to have to come
up with a pretty compelling and convincing theory (along with some
side-by-side, all-other-things-equal proof) for that one.



> Are there any other performance or design considerations that might lead
> manufacturers away from open face blocks?

Tradition, certainly. Steinway did it that way back in the 1860s and 1870s
so it must be the right thing to do. But, of course, they were also using
three-ply blocks back then and depended on the pin riding forward and
resting against the iron plate at the bottom of the hole to keep from
splitting those block to shreds.

I am not aware of any performance or design benefits to the closed-block
system. I would guess that the closed-block system is now some cheaper for
most manufacturers. Especially if they depend on pin/pinbushing contact for
support. Pinblock-to-flange is a sometime thing for most modern
manufacturers and CNC machinery can handle either with equal aplomb.

In favor of the open-face design is ease of tuning and, when properly
designed and fabricated, somewhat improved tuning stability.

Del