Vertical Hitch Pins, was [CAUT] duplex position

[pianoguru at cox.net]

---- 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