soundboardinstal again

[David Love]

I believe go bars can be calibrated based on thickness, type of wood (ash
or hickory) and length.  You have to have a way of setting the piano at a
controlled height below a top deck.  Then by using go bars of a specific
length differential between the top of the bridge and the top deck, and the
go bar itself, the amount of force given by each go bar can be determined. 


David Love
davidlovepianos@earthlink.net


> [Original Message]
> From: Farrell <mfarrel2@tampabay.rr.com>
> To: Pianotech <pianotech@ptg.org>
> Date: 7/24/2003 2:58:17 AM
> Subject: Re: soundboardinstal again
>
> How are you calibrating your go-bars? A scale? Calculated beam deflection?
>
> Terry Farrell
>   
> ----- Original Message ----- 
> From: "David Love" <davidlovepianos@earthlink.net>
> To: "Pianotech" <pianotech@ptg.org>
> Sent: Thursday, July 24, 2003 3:51 AM
> Subject: Re: soundboardinstal again
>
>
> > I've always been curious why people use wedges to prestress the board. 
Why
> > not use go bars along the bridge line with which you could actually set
the
> > amount of load you were putting on the board--not to mention distribute
the
> > load in a more controlled way.  By doing this, you would then be able to
> > see how the board reacts under 750, 850, or 1000 lbs and set the bearing
> > based on where you wanted the board to end up.  Though the effect of
> > various loads can, apparently, be precalculated, I would think there
would
> > still be some variability.  This would seem to take that variability, or
> > lingering doubt, out of the equation.  It would also seem to be quite
> > useful on old boards when recapping them.  Since older boards vary
quite a
> > bit in terms of stiffness, this would seem to offer a good way of
> > determining just how much bearing an old board could take without
pushing
> > it too far.  Or is this using a cannon to kill a fly.  
> > 
> > David Love
> > davidlovepianos@earthlink.net
> > 
> > 
> > > [Original Message]
[link redacted at request of site owner - Jul 25, 2015]
> > > To: <davidlovepianos@earthlink.net>; Pianotech <pianotech@ptg.org>
> > > Date: 7/22/2003 11:59:56 AM
> > > Subject: Re: soundboardinstal again
> > >
> > > David Love wrote:
> > > > John:
> > > > 
> > > > I don't know if you are rib crowning or compression crowning, but
might
> > > > that difference be explained by changes that occur due to
compression
> > after
> > > > the board is installed?
> > > > 
> > >
> > >
> > > I don't think the method of crowning will make a difference here.
What 
> > > compression are you talking about? If you are talking about the SB 
> > > picking up moisture, yes that could make it stiffer. But my
observations 
> > > are made with the SB at the same moisture content (or very close) so 
> > > there will not be any additional compression (this compression would 
> > > happen with either a rib crowned board or a panel crowned board). I
am 
> > > talking about the difference in SB stiffness (resistance to load) 
> > > between dry clamping into the case and gluing it in. I notice an 
> > > increase in stiffness. I interpret this to mean that a soundboard 
> > > receives additional support from being firmly attached to the case. 
> > > Because I use wedges to pre stress the board before setting  or 
> > > adjusting bearing I can feel how stiff the board is. I suppose if you 
> > > didn't use the wedges you may not notice this. The soundboard is like
a 
> > > stiffening spring, it gets firmer as you press it down. I notice the 
> > > increased stiffness at the bottom of the pre stressing, the slack
area 
> > > at the top seems to remain fairly loose. I usually find I need to
lift 
> > > the plate up 2mm or more in the middle and bass. The treble remains 
> > > pretty mush the same. This is fairly predictable and Steinway plates
are 
> > > easily adjusted (with the plate dowels not the plate bolts) before 
> > > securing the plate down and stringing.
> > >
> > > John Hartman RPT
> > >
> > > John Hartman Pianos
[link redacted at request of site owner - Jul 25, 2015]
> > > Rebuilding Steinway and Mason & Hamlin
> > > Grand Pianos Since 1979
> > >
> > > Piano Technicians Journal
> > > Journal Illustrator/Contributing Editor
[link redacted at request of site owner - Jul 25, 2015]
> > >
> > 
> > 
> > 
> > _______________________________________________
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