False Beats

[Farrell]

Very interesting experiment. Your "string offset angle which is often below
10 degrees" - the string offset being the angle that the string makes as it
goes from the speaking length and bends around the first bridge pin? And
that angle being controlled by the placement of the rear bridge pin. Am I
right? Just making sure. Thanks

Terry Farrell
Piano Tuning & Service
Tampa, Florida
mfarrel2@tampabay.rr.com

----- Original Message -----
From: "Ron Overs" <sec@overspianos.com.au>
To: <pianotech@ptg.org>
Sent: Tuesday, September 05, 2000 5:48 AM
Subject: RE: False Beats


> David, Ron, Richard and list,
>
> David wrote;
>
> >. . . .   I can think of hundreds of grands, especially
> >Japanese/Korean, where I could visibly see the string drop to bridge cap.
> >Another tap wouldn't move it.
>
> So often these makers use bridge pin inclinations which are insufficient
and a string offset angle which is often below 10 degrees.
>
> I learned a lesson the hard way a recently. Ten degrees of string offset
angle and twenty degrees of pin inclination certainly works well.
>
> In July we completed a new piano for the Australasian Piano Technicians
Convention. The piano was a modified Samick 225. We designed a new scale and
made new bridges, along with many other design changes. This piano was the
first to get our new grand piano action.
>
> However, during the design phase of this project, which was rushed to say
the least, I made an error in a spreadsheet formula while working out the
bridge pin locations to set the string offsets. Unfortunately, this error
resulted in string offsets which were pretty close to zero in the top two
sections. I discovered this problem just before the piano was to be strung,
and too close to the convention to rectify. Therefore, we were compelled to
string the piano, warts and all, since it was to be an exhibit at the
convention.
>
> I was not too pleased with the tonal qualities of the treble section.
While it was just acceptable, it had none of the clean tonal qualities which
I had expected. Indeed the piano was so false as to be difficult to tune.
After the convention we stripped the piano down and recapped the offending
sections. We are now delighted with the tonal qualities of the treble. The
only difference between the two bridge caps was the string offset angle -
yet the tone was radically improved.  For the second take, the bridge pin
positions were transferred from the spreadsheet to a CAD drawing of the
piano. The drawing scale was adjusted to produce an accurate 100% print out
on our Epson inkjet. The print out was placed on the blank bridge caps,
which allowed us to punch the marks through to the bridge cap. Using this
system we were able to get the highest bridge pin location accuracy we have
had to date. I have suspected for while that insufficient string offset
angle to contributes to falsen!
> ess. The bungled bridge cap saga prove it>
> Ron O
>
> Overs Pianos, Sydney Australia
> -------------------------------
> Email:   sec@overspianos.com.au
> Website: www.overspianos.com.au
> -------------------------------
>
>
>