Bridge pin spacing (was Baldwin SD-10)

[Tom Servinsky]

Ron,
Have you spoken to Del Fandrich about is notcher. Sounds like you are
designing the same one he currently uses.
Tom Servinsky
----- Original Message -----
From: "Overs Pianos" <sec@overspianos.com.au>
To: <pianotech@ptg.org>
Sent: Friday, September 07, 2001 10:17 PM
Subject: Re: Bridge pin spacing (was Baldwin SD-10)


> Phil, Ron N and all,
>
> >  > . . . and how
> >  >manufacturers decided on that spacing.
> >
> >. . . there's more aggravation to be had on this subject. The
> >farther apart the
> >row spacing, the less precision required in lateral pin placement to
> >achieve a target stagger angle. The closer the spacing, the greater the
> >required precision. Meanwhile, if I was designing the bridge, I'd want
the
> >pins in far enough from the edges for good support, yet close enough to
the
> >edges to minimize the amount of wood I'd have to remove to cut the
notches.
> >No sense making life harder than it has to be. That means that as the
> >bridge angle relative to the strings narrows, I'd increase the row
spacing.
> >It takes a little more time and thought in planning and layout, but
> >anything that cuts down (sorry) notching labor is definitely my friend. I
> >make nice clean notches, mind you, it's just that I don't much enjoy
doing
> >it. Maintaining the row spacing through the whole piano works fine too,
but
> >you spend more time hunkered over a chisel producing it. Someday, a power
> >notcher.
>
> Indeed and what a useful labor saving device it will be. A power
> notcher is at the CAD stage in our workshop as you speak.
>
> >Of course, if you are working with a re-capped bridge on a soundboard
that
> >isn't being replaced, you can't mess around too much with row spacing
> >unless you want to rescale with the newly resulting speaking lengths. Not
> >that it's a problem, but it bears consideration. If by the happiest
> >circumstance, you're making your own bridges, you can correct the log
> >progression deviations across the treble breaks, smooth the transition
> >across the bass/tenor break, and generally build about anything the plate
> >will let you get in the piano. That's when it gets fun.
> >
> >Ron N
>
> Good post Ron. In the lower bass we might prefer to keep the
> front/rear spacing distance to a practical minimum for the bass
> singles, to gain the longest possible back scale in shorter to medium
> length scales. When using a spreadsheet to design the top elevation,
> it is worth making the front/rear spacing gradually increase in the
> tenor region as the bridge angle relative to the strings narrows, to
> satisfy the objectives Ron N writes about.
>
> Another area of bridge layout which some manufacturers occasionally
> ignore to their peril is the bridge pin spacing between adjacent
> unisons. This spacing should allow for the provision of sufficient
> bridge wood between pins to allow for adequate pin support. If the
> spacing is insufficient, there is a risk of the cumulative side
> bearing on each pin group causing cap failure. Some of the smaller
> Grotrian designs of the sixties and seventies were particularly prone
> to this 'disease'. Some years ago a client of mine purchased a
> replacement bridge cap from the factory, in which the pin spacing was
> so tight that there was just room for the wire between the pins -
> what a disaster in waiting (no surprise then that the original bridge
> of his 220 had failed). Surprisingly, the earlier Grotrians (1920s)
> were better designed in this respect. Why was the design expertise
> which clearly existed at the factory at an earlier time lost? Perhaps
> contemporary designers should start out by learning all the old
> tricks first.
>
> Ron O
> --
> ______________________________
>
> Website:  http://www.overspianos.com.au
> Email:        mailto:ron@overspianos.com.au
> ______________________________