[CAUT] Restringing treble

[Bob Hull]

I do not know what kind of contact there was between
the plate and ledge before. I wish I would have
checked for that.   But, the bottom of the plate
doesn't have any type of protrusions.  

Bob Hull

--- David Love <davidlovepianos@comcast.net> wrote:

> Are you sure that the plate had continuous contact
> to begin with?  The
> plate may have had small protrusions around the
> point of the perimeter
> bolts which contacted the ledge when tightened. 
> Thus, further
> tightening the plate bolts would not give greater
> contact to all areas
> of the plate.  Plates will routinely flex quite a
> bit around the
> perimeter, which isn't to say that one should
> routinely employ the use
> of liberal plate flexing to accommodate the
> necessary bearing.  But you
> do see it.  
> 
> 
> David Love
> davidlovepianos@comcast.net 
> 
> -----Original Message-----
> From: caut-bounces@ptg.org
> [mailto:caut-bounces@ptg.org] On Behalf Of
> Bob Hull
> Sent: Saturday, January 01, 2005 8:43 PM
> To: College and University Technicians
> Subject: Re: [CAUT] Restringing treble
> 
> 
> Questions about this theory: If the plate is able to
> flex like this then why am I having the following
> experience:
> 
> I have just done soundboard repairs on an older 5'
> 6"
> Weber grand including coating the board with epoxy.
> Instead of resting on dowels the plate sits on a
> continuous ledge about 1/2 inch (12.7 mm) high
> around
> the perimeter of the soundboard. In order to
> increase
> the downbearing I have lowered this ledge to approx.
> .42 (10.6 mm).  The db will still be minimal but I
> don't want to overstress this old board.  Since it
> was
> difficult to know just how this lowered ledge
> surface
> would mate to the bottom of the plate,- where the
> two
> would meet-, I used slips of paper between the
> bottom
> of the plate and the top of the ledge (like when
> bedding a keyframe) to feel where the two were
> meeting.  I found there was a small gap between the
> two -  enough to freely slide the paper strips along
> almost the entire area(if the paper was .003 then
> the
> gap was maybe .006 but I hadn't tightened the
> perimeter screws yet. It did have contact with three
> small areas.   Surely when I tightened the screws
> the
> little gap would disappear  - right?, the plate is
> somewhat flexible as you have been discussing - 
> but,
> tightening the screws did not eliminate the gap or
> change it as far as I could detect.
>     I lowered the places where there was contact 
> which still didn't improve the mating of the plate
> and
> ledge.  So, I created highpoints or resting spots
> (using WEST epoxy)on each side of each screw as if
> it
> was sitting on really short "dowels".  Protecting
> the
> board and plate with wax paper I lowered the plate
> back down and tightened the screws to make the epoxy
> fit the gaps - - like pinblock final fitting. 
> Of course, if I remember correctly the plate is
> thicker around the edge and maybe it's elasticity is
> too limited there to flex.  The plate as a whole is
> more capable of flexing/bowing because it is a
> lengthy
> span which is anchored around the perimeter and at
> tiny nose bolt locations. The original design, if
> the
> plate and continuous ledge were well mated, seems
> like
> it would have a different effect on plate behavior
> characteristics than a plate that rests only on
> dowels
> or lag screws. 
> 
> A long explanation to ask "Why didn't the plate flex
> down when the screws were tightened?" 
> Also, what other/better ways would you have
> approached
> this plate height situation? 
>   
> --- Ron Nossaman <rnossaman@cox.net> wrote:
> 
> > 
> > >It seems to me that the following may  prove this
> > theory.
> > >
> > >The next time you experience a broken string,
> > measure the pitch change on 
> > >adjacent strings/notes. Then press down on the
> > bridge about 7 lb. worth. 
> > >If there is no effect on the pitch on these
> > adjacent strings, you will 
> > >know it is not the downbearing change on the
> bridge
> > causing the pitch 
> > >change. After the new string is installed, check
> > the adjacent strings again.
> > 
> > If someone who uses an ETD tries this, please post
> > the results to the list.
> > 
> > 
> > >Do you think this will prove the point? I've not
> > done this, but I will do 
> > >this the next time the situation occurs. This has
> > been enlightening, 
> > >because I've always heard that pitch change takes
> > place due to the change 
> > >in downbearing on the bridge and soundboard.
> > >
> > >Sincerely,
> > >Gary Mushlin, RPT
> > 
> > All of us have always heard that, but I don't see
> > much indication that it's 
> > true.
> > 
> > Ron N
> > 
> > _______________________________________________
> > caut list info:
> > https://www.moypiano.com/resources/#archives
> > 
> 
> 
> 
> 
> 
> 		
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