Bass Bridge Position

[David Love]

Del:

I'll have to reexamine my scale chart as it relates to the plate.  The
reason I originally chose to go to note 32 is that I am using the original
long bridge (cut down) and that is the point at which the bridge starts
hockey stick back the other way.  I was able to run a virtually undisturbed
log scale through note 33 but at note 32 it pushed the speaking length back
very close to the plate and almost off the bridge.  If I shorten note 32 in
order to fit it comfortably on the bridge it drops the tension down into the
140 lb range unless I create an inharmonicity bump (not a big one) between
the transition bridge and the plain wire section by increasing the string
diameter for a single unison at note 32.  In terms of tuning weirdness it
seemed like 6 of one... At least F33 is still plain wire.  

A quick check of the piano suggests I could get 1300 mm at A1 with about 10
mm space to the plate.  Does that extra 25 mm of backscale make an audible
difference?  


David Love
davidlovepianos at comcast.net 
www.davidlovepianos.com

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Delwin D Fandrich
Sent: Monday, March 10, 2008 3:26 PM
To: 'Pianotech List'
Subject: RE: Bass Bridge Position

David,

My current Model O scaling calls for five notes on the transition bridge
(making
life easier for the tuner), 12 notes of wrapped mono-chords and 14 notes of
wrapped bi-chords. I have two scales in my records that are now my
standards.
One has an A-1 speaking length of 1325 mm, the other is 1300 mm. I prefer
the
latter if everything works out and the phase of the moon is just right.

And, yes, the extra backscale length is worth going after.

Del
Delwin D Fandrich
Piano Design & Manufacturing Consultant
620 South Tower Avenue
Centralia, Washington 98531  USA
Phone  360.736-7563
<mailto:fandrich at pianobuilders.com> 

| -----Original Message-----
| From: pianotech-bounces at ptg.org 
| [mailto:pianotech-bounces at ptg.org] On Behalf Of David Love
| Sent: March 10, 2008 9:21 AM
| To: 'Pianotech List'
| Subject: RE: Bass Bridge Position
| 
| I'll look at that again.  At the moment I have the transition 
| 27 - 32 with
| 32 at 850mm and 27 at 975 (F33 is 935).  A#2 (note 26) is at 
| 896 and A0 is 1320.  As I mentioned, I could move the bass 
| bridge a bit more forward and gain maybe 15 or 20 mm of 
| backscale length.  Putting the transition up to note 32 
| definitely gets the bottom of the tenor bridge away from the 
| bottom of the bass bridge. 
| 
| The overall tension on this piano is about 37000lbs and I've 
| tried to keep it down there as it's an older O without the 
| cross strut between the tenor and bass long struts (on the 
| plate).  Not sure if that's a factor but plate failure is 
| something I don't care to think about.  I've smoothed it out 
| but kept the plain wire tensions in the mid 150s drifting 
| only slightly higher at the upper end.  
| 
| David Love
| davidlovepianos at comcast.net
| www.davidlovepianos.com
| 
| -----Original Message-----
| From: pianotech-bounces at ptg.org 
| [mailto:pianotech-bounces at ptg.org] On Behalf Of Ron Nossaman
| Sent: Sunday, March 09, 2008 8:37 PM
| To: Pianotech List
| Subject: Re: Bass Bridge Position
| 
| 
| > Looking at it again I could actually move it up fairly 
| easily without 
| > any plate grinding since there is a bit of room from where 
| A0 crosses 
| > and the end of the bridge.  My scale experiments suggest that this 
| > scale looks a
| bit
| > better with 12 or 13 monochords in the bass instead of 10.  I'd be 
| > curious to know how many notes on your transition and what the 
| > speaking lengths at the beginning and end were.
| > 
| > David Love
| 
| I left the monochords at ten, and ended up with an A-0 length 
| of 1308mm, and transition lengths of 987 at B-2. and 932 at 
| D-3. Four notes. It worked real pretty in the spreadsheet, 
| and the bridge placement and lengths sound (so far) like I 
| won't need any mass loading or even voicing to smooth the 
| transition. It's very smooth right out of the box, and I 
| don't even have the hammers squared up and strings mated to 
| them yet. I seem to have come pretty close.
| 
| Ron N
| 
| 
|