Mother in Law of All Cutoff Bars

[Delwin D Fandrich]

----- Original Message ----- 
From: "Phillip Ford" <fordpiano@earthlink.net>
To: "Pianotech" <pianotech@ptg.org>
Sent: August 29, 2003 1:11 PM
Subject: Re: Mother in Law of All Cutoff Bars


> >Del
>
> One of the interesting things about this plate is that in spite of
> all the metal they put at the tuning pin end, it's fairly light at
> the hitch pin end.  The struts are heavy, but the plate web in
> between looks like it might be fairly flexible.  For the strings at
> the midspan between the struts, I would think that there might be a
> fair bit of deflection at the hitch pin end as they are pulled up to
> pitch.

Yes, I noticed that. Though I'm not sure how flexible it might be. There
really isn't all that much stress on the hitchpin panel considering its
overall strength and stiffness. I've not done any kind of stress analysis
on this but I have taken some general measurements. Most hitchpin rail
designs are way overbuilt for what they have to do.


>
> I haven't really thought about it before, but I wonder if this could
> be a way to attempt to build in some tuning stability.  The humidity
> increases, the soundboard moves up, the string tension increases, but
> because the plate or string connection to the plate is fairly
> flexible, the tension won't increase as much as for a rigid plate or
> connection.  I don't know how flexible things would have to be to
> make this work (if it would) or how that would affect the tone.
> Also, if you were counting on plate flexibility for this effect, you
> wouldn't get any at the plate struts.
> Too bad we don't know more about what these guys were thinking.

Yes, it is. Personally I doubt they were trying to get all that
sophisticated and/or tricky with their plate castings. Most of these piano
builders were not engineers. Nor did they often employ engineers to work
out any kind of stress analysis. When they did they tended to treat the
things as if they were auto or train bridges. (See the appropriate
discussion in 'Piano Tone Building.')

I'd sure like to see a lot of that iron taken out of plates. So, I tend to
think, would a lot of prospective customers in our ever-more-mobile modern
society.

Del