From "Frank Emerson" <pianoguru@earthlink.net>
I would say that ALL pianos are designed with a straight strike line. It's the first line on a blank sheet of paper (or computer screen), in the design process. Having said that, someone from this list will try find an example to prove me wrong, but it is not Baldwin. Somewhere along the way, someone at Baldwin discovered that the sound could be improved by altering the strike point. Indenting the hammer line was an easy fix. Sometime later, it was fixed right, by altering the plate and bridge to conform to the "new" strike point and restore the straight hammer line.
Frank Emerson
Original Message -----
From: Michael Spreeman
To: Pianotech List
Sent: 8/1/2007 11:25:08 AM
Subject: RE: Finding the strike line another method
Most pianos are designed with a straight strike line. There are a few exceptions, like the early Baldwin SD's which had a curved hammer line in the design. The problems being addressed by altering (or, better thought of as optimizing) the hammer line are construction related, not design related. There is ample room for human error from the starting point of a straight line drawing to final assembly. At the foundry, the cope and drag of the sand cast molds shift through the years which causes misalignment between the top and bottom of the casting. Send the miscast plate to an assembly line where the person grinding, shaping, and locating the Vbar surface is have having a bad day, has old worn patterns which are no longer true, and has to finish 20 plates by 5:00 rather than doing 6 plates correctly, and the stage is set for the Vbar to be most anywhere. Send the plate off to the rim for installation and have it not located correctly (too far forward, aft, left to right, too high, too low, etc), and it's anyone's guess where the once straight strike line has gone or even if the treble strike line is in the same universe as the design spec. The problem isn't Steinway specic. Any piano that has a ground Vbar is subject to error.
RE "hanging treble hammers": I like to hang samples in the treble by shimming the hammer with a small piece of traveling paper or whatever holds the dry-fitted hammer in place. Once the action is located in the "best" workable position (which many times is simply the least offensive compromise) sample hammers are dry hung to factory spec begining at #88 and working down every 4th hammer down into the middle of the killer octave. The remainder of the process is the same as everyone has been talking about; put the action in, make sure the piano is at pitch, and position each hammer by ear, pull the action, glue on the hammers in between the samples, then glue on the samples. This can be done in the customers home if the piano is not in the shop, and then the action can be taken with the samples back to the shop where the hammers can be hung. Yes, it results in some funky looking hammer lines, but at least the sound is optimized, and yes, the strike point of each hammer is mathmatically correct. It is possible to relocate and make the necessary corrections to be able to have a nice straight hammer line when rebuilding, but the time and effort necessary usually cannot be justified financially.
Michael C. Spreeman
http://www.spreemanpianoinnovations.com
> Date: Thu, 26 Jul 2007 06:23:41 +0100
> To: pianotech@ptg.org
> From: JD@Pianomaker.co.uk
> Subject: Re: Finding the strike line another method
>
> At 6:52 pm -0700 25/7/07, David Love wrote:
>
> >So you?ve obviously found some consistency in this requirement. I
> >guess it makes sense since I would presume it?s related to the plate
> >design or casting. Looking back, though, I?m not sure I?ve seen the
> >need in every example. Maybe it?s time to go back and visit those
> >pianos?maybe later.
>
> In theory the strike point will be at a certain fraction of the
> speaking length, say 1/8 in the area under discussion, and since the
> strike line is the first line drawn in designing a piano, it would be
> very odd to think it was not drawn straight in the horizontal plane.
> When you, or Dale, have set up the piano with the curve in the line
> to get the best tonal result, do you find that the hammer is striking
> the string at different proportions of the speaking length?
> Supposing that the strike line is straight, it would take a very
> large error in the casting to require a difference of 4 mm in the
> positioning of the hammer-head on the shank.
>
> Am I right in assuming that Steinway's original set-up has the
> hammer-line straight? If so, is there a curve in the string height
> or the hammer bore such that the strike point is on the strike line?
> I have practically no experience with the 'B' and am fascinated to
> know why it is that a curve in the hammer gluing should produce the
> best sound to your ears, which I do not doubt.
>
> JD
>
>
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