Vertical Hitch Pins, was [CAUT] duplex position

[Richard Brekne]

Hi Frank.

First let me say I have to admire the calm and dispassionate way in 
which you keep presenting your perspectives here. A very refreshing 
exception to the rule.

I was particularly interested in two points you make below. First the 
one about the Baldwin claim to be able to take care of duplex lengths 
despite the "third string" always being rather impossible. The 
interesting bit is that they saw fit to defend that duplex issue at all. 
This is not to foreign to argumentation I have heard here... that one 
can design back lengths in that <<sound better>> then tuned duplexed 
lengths by the use of vertical hitch pins. Such a claim directly 
contradicts any claim that placement of duplexers is meaningless. Yet 
both these claims seem to be made by the same folks in certain places of 
the world... and I don't just mean here and I don't just mean on one or 
the other side of the issue.

The other bit I find very interesting is your point about the stresses 
on the plate a vertical hitch pins creates. I take it as a given that 
Baldwin figured this into their equation when designing their plates... 
but simply installing vertical hitch pins in a plate where this was not 
designed into the thing to begin with does strikes me as risky at best. 
A lot can occur besides simple plate failure. The issue of field techs 
being able to move adjust the strings position on the vertical hitch pin 
has been up many times... and has a certain degree of validity IMHO. 
Indeed that was one of the reasons given why S&S stopped making 
adjustable front duplex bars way back when.

One of the things I appreciate so very much about Ron Overs approach 
towards giving advice on more advanced redesign issues touches directly 
on this kind of thing. He has this big disclaimer side warning folks on 
all levels that they simply need to know what they are doing before 
making such changes. More or less underlines in bold that its far too 
easy to overestimate ones own knowledge.

Anyways... thanks for the informative posting.

Cheers
RicB



        ---- Richard Brekne <ricb at pianostemmer.no> wrote:
         > I doubt your position is an unpopular one to take since all
        but a
         > handful of the piano builders / designers I've met opt for
        them. I
         > think its fair to say however that the use of vertical hitch
        pins
         > without duplexers can be successfully used in piano design as
        well.


    Yes, duplexers, as opposed to vertical hitch pins, are more common
    in modern production of new pianos, but the reverse seems to be the
    preference among rebuilders/redesigners on this list.

    I would also agree that vertical hitch pins have successfully been
    used. As I said, I have used them myself, and have been satisfied
    with the results. Still, in the final analysis, I prefer traditional
    duplexers to vertical hitch pins in my current work.

         > Curious as too your objection to vertical hitch pins.
        Personally I don’t
         > see the big deal either way...


    It's not a big deal either way, but here are a few of my reasons for
    my preference:

    Baldwin claimed to preserve duplex scaling with vertical hitch pins.
    That works (to some extent) with strings that are common to a single
    unison, but strings that are shared by two unisons can only satisfy
    the tail length of one note, but not the other. More importantly,
    the duplex, tail length, is fixed (not adjustable). Getting the
    "duplex/tail length" in the "ball park" is not good enough for me.
    If it cannot be "tuned" to the desired relationship to the speaking
    length, it's not worth bothering with it.

    Vertical hitch pins transfer the force of the string tension high
    enough on the pins to create a radically different leverage on the
    plate. Where the string tension is applied to the bottom of the
    hitch pin, the forces applied to the plate are minimal. Where the
    force of the string tension is applied 6-12mm above to surface of
    the plate, the mechanical (dis)advantage of the leverage applies a
    significantly greater stress on the plate casting. I have seen plate
    cracks along the line of vertical hitch pins, where it would never
    have occurred with traditional hitch pins.

    I remember a time when the rolled pins where not hardened to the
    specified hardness. I don't remember how many pianos were effected,
    but I would say they was in the hundreds. The pins bent, and every
    piano effected had to be reworked. Since this was an error of a
    vendor of a vendor, it was not an easy problem to fix.

    Since setting bearing was deferred until after the string is drawn
    to full tension, there is a wide margin of error. I remember pianos
    soundboards failing with a loud bang, the soundboard pulling up, and
    breaking free from the belly rail in the high treble. This would
    never have happened with traditional hitch pins.

    Finally, vertical hitch pins open the piano to devastating results
    from unknowledgeable techs making misguided changes in down bearing.
    I hate to say this on a piano tech list, but I have seen the results
    of such misguided movement of the strings on vertical hitch pins. I
    would prefer to permanently set the bearing in the manufacturing
    process, in a way that cannot be compromised by well-meaning, but
    misguided techs.

    Frank Emerson