Veritcal hitchpins?

[Delwin D Fandrich]

| -----Original Message-----
| From: pianotech-bounces at ptg.org 
| [mailto:pianotech-bounces at ptg.org] On Behalf Of Ron Nossaman
| Sent: October 21, 2007 10:15 AM
| To: Pianotech List
| Subject: Re: Veritcal hitchpins?
| 
| 
| > The closer the loop is to the plate, the less the torsion on pin. 
| > However, not knowing the math on these things I am 
| enquiring on your 
| > empirical experience.
| >  
| > /Jim I/
| 
| It's not torsion on the pin, it's flex - bending stress. In 
| any case, no. Tuning stability doesn't seem to be affected by 
| loop altitude, but the lower the loop, the less stress there 
| is on the plate, and the better the odds of not breaking it.
| Ron N

Well, within limits, anyway. Back in my days at Baldwin I saw (and tried to
correct) the production people setting the strings as much as 18 to 19 mm off
the plate surface. Why the plates didn't break is still a mystery. Perhaps some
did but I just wasn't aware of them.

I've used a 5 mm limit for some time but it is a bit arbitrary. I believe this
to be a safe maximum for older plates. I came up with it by measuring a variety
of original string rests and string bearing bars (both cast-in and loose) most
of which are in the 4 to 5 mm range (or less).

Del