[pianotech] Increasing bridge height

Will Truitt surfdog at metrocast.net
Sun Mar 22 15:09:00 PDT 2009


Hi Del:

 

Thank you for your input.  

 

I am already using an adjustable bolt system as you describe and will do the
same on this Steinway.  As for the pinblock, it is my custom to start with a
pinblock that is too thick, and then fit it to the underside of the plate as
well as the flange, then plane it down to the needed thickness.  Here I
would only start with a block that  is thicker still, and then plane it down
to the target thickness which will achieve the desired height for the plate
after fitting.  Likewise at the rim end, start by measuring the height of
the plate before teardown in several spots, then set the plate at the
targeted difference above those values after the plate goes back in, and
then set bearing at the bridges.  

 

This board will have a rib scale and panel thickness that is calculated to
match the string scale  (I'll be working with Jude Reveley on that).  I just
wanted to know if the additional bridge height was a sufficient factor that
it would need to be addressed and the rib scale modified.  

 

Thanks for your sense of a target value for a bridge height.

 

Given how much string heights vary with Steinways, I will certainly have to
wait until the piano is strung before I start action fitting, and then find
out where I am with it, and adjust accordingly.

 

Are others finding that the increased bridge height and higher string plane
requires new damper wire, the old being too short?

 

Will Truitt

 

From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Delwin D Fandrich
Sent: Saturday, March 21, 2009 5:22 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] Increasing bridge height

 

I don't really like treble bridges that are 24 to 25 mm tall. I want to end
up with a bridge height of at least 30 mm at C-88.

 

Yes, this means raising the plate. Start by making the pinblock a bit
thicker. Or shim as needed.

 

Don't bother with longer dowels, use an adjustable bolt system of some kind.
You can either make your own using cap screws and lock nuts (as I do) or buy
one of those currently available.

 

No, I do not alter the rib dimensions to accommodate the taller bridge. It
doesn't really matter to me what the original ribs were like--I'm setting up
my rib scale and soundboard thickness to match the string scale and am
assuming a bridge of reasonable height. Small S&S pianos use relatively low
tension scales so the board is going to be relatively thin and the ribbing
is going to be on the light side.

 

I do sometimes reset the height of the action but you may find it fits the
raised string height just fine. I.e., it was originally set up for a plate
setting some higher than it ended up. 

 

ddf

Delwin D Fandrich
Piano Design & Manufacturing Consultant
620 South Tower Avenue
Centralia, Washington 98531  USA
Phone  360.736.7563
Cell  360.388.6525
Fax  360.736.5239
 <mailto:E-maildel at fandrichpiano.com> E-mail 1: del at fandrichpiano.com
E-mail 2:  <mailto:ddfandrich at gmail.com> ddfandrich at gmail.com

 

 

 

 


  _____  


From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Will Truitt
Sent: March 21, 2009 3:06 PM
To: pianotech at ptg.org
Subject: [pianotech] Increasing bridge height

To the best minds of our generation (at least regarding soundboards):

 

I just pulled a two bridge 1909 Steinway 6' 1" A into the shop for a total
soup to nuts rebuild, which will include a new soundboard.  I recall some
discussion in the past on the forum about increasing the bridge height in
Steinways (which some feel is too low) to increase mass and stiffness.
David Love and Ron Nossaman's names come to mind.    I seem to remember talk
of increasing the thickness of the bridge by about 4 mm over the thickness
of the original.  Since I am putting a new board in this piano and will be
setting plate height for global bearing values on adjustable plate bolts as
well as setting downbearing on the bridge cap, I am considering the
possibility of doing this.  I would  bore my hammers to make the appropriate
accommodations there, as needed

 

My questions are:

 

What are the tonal benefits that you feel are derived by increasing the mass
and stiffness of the bridge by increasing the height?

 

Increasing the bridge height will require raising the plate around the rim
with the adjustable plate bolts or dowel system to achieve desired bearing
values.  Are you increasing the thickness of the pinblock by a
corresponding amount to raise that end of the plate too?

 

Since the treble bridge is in effect another rib, albeit one running at
approximately right angles to the other ribs, are you making any
accommodation in the design of the ribs for these changes?

 

Does increasing the plate height require any other accommodations in the
action set up other than boring the hammers for the new string height?

 

I find this idea very intriguing.  Several years ago I sold a 6' 7" Kimball
Viennese Edition grand piano out of my shop for a customer.  While not
having a particularly elegant tone, it had outstanding volume and sustain
throughout, particularly in the treble.  What makes this interesting was the
fact that the  treble bridge heights were 39 to 41 mm. - a pretty tall
bridge.    Obviously this would not be the only thing that contributed to
these tonal qualities, but I cannot help wondering if it were a significant
ingredient.  

 

I look forward to the thoughts of all contributors.

 

Will Truitt

 

 

 

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