Bridgetop Extravaganza Revisited

[Farrell]

Hello Jon. JPG me, please. Exactly what natural curve are you trying to remove?

Terry Farrell
  
----- Original Message ----- 
From: "Jon Page" <jonpage@attbi.com>
To: "Pianotech" <pianotech@ptg.org>
Sent: Wednesday, December 18, 2002 7:18 AM
Subject: Re: Bridgetop Extravaganza Revisited


> I wouldn't trust a shallow fill of epoxy to resurface the cap, recap.
> 
> As far as pounding the string, I agree that it is over-rated and have
> tapped the bridge pins as Roger Jolly suggested to relieve false beats.
> I also devised a tool for removing the natural curve from the wire at the pins
> to improve the termination. I posted to the list a few years ago about it,
> I have a jpg file if any one is interested in viewing it.
> 
> Regards,
> 
> Jon Page
> 
> At 02:13 AM 12/18/2002 -0800, you wrote:
> >     Hi All,
> >Just joined,  first post to this or any other group.  Serendipitous 
> >timing, just read all the recent bridgetop/ bridgepin posts.  Have a 1985 
> >Stwy D in the shop for action overhaul and restring.  I thought I was 
> >noticeing something funny about the bridges but was in denial until I 
> >started taking all the teardown notes.  The plain wire strings have been 
> >pounded (seated) into the bridge so that at the edges there is more wire 
> >diameter below the bridge top than above it.  When viewed from the side 
> >the wire makes a pronounced curve up onto the bridge and down again out 
> >the rear making accurate component readings impossible to do from on top 
> >of the wire.  It was showing negative front bearing until I realized what 
> >was happening and started using the actual bridgetop as 
> >reference.  Situation is most severe at capo sections and diminishes down 
> >to what looks like normal grooves to me under the bass 
> >strings.  Deflection in strung piano is .5 deg at bottom of low 
> >capo,  1-1.5 deg rest of capo sweeping up to 2.5 deg at note 88.  There is 
> >.250" crown at low capo.  (measured from top of board)
> >     Is it possible this condition is due to the quality of the capping 
> > material?   I usually work on much older instruments.  I have never seen 
> > string cuts like this.  Also the various pressures have caused dead wood 
> > to swell up and check here and there around the terminations.  Again I'm 
> > not used to seeing this.  Inspection of the pins under magnification 
> > shows the string resided in two distinct locations.   My theory:  Pre- 
> > and Post Pounding.  There are also a lot of unexplainable nicks on the 
> > side of the pins.  The pins pull out easily.  No cracks to speak 
> > of.  This is an institutional piano which has probably been in Southern 
> > California its whole life.
> >     What I'm thinking about doing is similar to what Dale Erwin just 
> > posted.  I've never done the epoxy bridge thing but I'm familiar with the 
> > nasty stuff. I'm imagining thickening it enough with colloidal silica so 
> > it won't run down the notches or too much into the holes and applying it 
> > with a small spatula.  I want to fill those deep grooves (at least on the 
> > speaking side) and then sand the top flat.  If I put the stuff on in the 
> > morning can I pare/renotch and redrill at the end of the day before it 
> > gets too hard and while I can still find the original holes?
> >     Looking forward to peoples responses.
> >
> >     I want to stop using the misnomer "string seating" in favor of wire 
> > straightening (or something similar)  which is what I do at a low lateral 
> > angle (around the bridges anyway).  I have never been convinced of the 
> > need of downward tapping pressure at the bridges.  For some reason this 
> > is one of the first things new technicians are taught and the thought of 
> > them going around with little hammers and pounding on pianos scares 
> > me.  We straighten wire for control of damper and hammer contact and for 
> > quick stabilization of new strings.  Perhaps having the wire come 
> > straight out of the bridge helps the string to vibrate in a more 
> > perpendicular plane even.  I don't really know.  After you take a few 
> > pianos apart you find that even in a negative bearing situation the 
> > angled pins hold the string tight to the bridge.  If there is so much 
> > negative bearing that they don't then no amount of pounding will hold 
> > them there.  But I guess that is another thread.   Right now I need help 
> > getting out of this mess.  I have finally accepted I have to pull the 
> > plate.  So much for the quick restring of a fairly new instrument.
> >
> >Thanks,  Steve Bellieu
>