[pianotech] cutting down a MH bridge

[David Love]

The bridge adds stiffness and mass to the system which raises the impedance.
I think it raises the impedance too much on those pianos because that's what
I hear.  I don't really calculate the bridge contribution to the system but
I have a preferred minimum and maximum based on my own experience.  The MH
bridge exceeds my preferred maximum and the sound that I hear reflects that.


 

I suppose bridge characteristics can vary with ribs, panel thickness (and
scales, for that matter) but I don't think you should substitute bridge
height for rib dimensions or panel thickness.  

 

For me, rib scales and panel thickness are related to string scale
(downbearing), size of the piano, number of ribs (of course), .  I don't
really see that the bridge should vary that much.

 

I think you will get different answers from different people as to what they
think is the best combination for the treble bridge based on their own tonal
preference and where in the treble bridge you are talking about.   

 

This piano (MH)  has a bridge that at C88 is 40 mm wide and 37 mm tall.
Compare that with a Steinway B also in my shop now that has  abridge that is
33 mm wide and 30 mm tall.  I would say that the difference in bridge
dimensions will account for some tonal differences.   The MH has a slightly
higher tension scale  but not enough to explain the need for a bridge that
much larger.  

 

Of course, you can make a system which is too high in impedance any number
of ways: ribs, panel, bridge.  But there probably is some ideal combination.
So far, left to my own devices, I prefer a bridge of somewhat smaller
dimensions.  My method of calculating rib scales is not, or at least I
prefer that not be, bridge dependent.    

 

David Love

www.davidlovepianos.com

 

From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Encore Pianos
Sent: Thursday, November 01, 2012 3:31 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] cutting down a MH bridge

 

How does it raise the impedence characteristics too much?   Why do you think
it raises the impedence characteristics too much?   How much is too much and
how much is just enough?  

 

Since we are dealing with mass and stiffness, what would be the best
combination for a treble bridge?

 

Should those characteristics for a bridge vary from piano to piano,
depending on the ribbing, panel thickness, etc. etc.?

 

Will Truitt

 

 

 

From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of David Love
Sent: Thursday, November 01, 2012 6:08 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] cutting down a MH bridge

 

I didn't state but I have always felt that the MH bridge was too massive and
raised the impedance characteristics too much.  

 

David Love

www.davidlovepianos.com

 

From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Dale Erwin
Sent: Thursday, November 01, 2012 2:33 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] cutting down a MH bridge

 

Did I miss why you want to cut it down /remove mass

Dale Erwin R.P.T.
Erwin's Piano Restoration Inc.
Mason & Hamlin/Steinway/U.S. pianos
www.Erwinspiano.com
Phone: 209-577-8397

 
  

 

-----Original Message-----
From: David Love <davidlovepianos at comcast.net>
To: pianotech <pianotech at ptg.org>
Sent: Thu, Nov 1, 2012 12:45 pm
Subject: Re: [pianotech] cutting down a MH bridge

Or possibly a router.  I was trying to figure out how to build and position
a guide so as to keep the cut a constant width through the curves without
having to freehand it.  
 
David Love
www.davidlovepianos.com
 
 
-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org
<mailto:pianotech-bounces at ptg.org?> ] On Behalf
Of Terry Farrell
Sent: Thursday, November 01, 2012 12:06 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] cutting down a MH bridge
 
I'll second what Ron said. And if you do go that route, I know a guy in
Florida that makes beautiful laminated bridges.
 
But if I were going to use the original, then yeah, I'd fire up the bandsaw.
You should be able to saw it pretty smooth freehand. Or you could make some
sort of post on your fence (like a several inch bump - maybe a vertical
board of maple rounded on the end at a right angle to the fence) right at
the blade - that way you would have a guide for constant thickness and yet
it would allow you to change the orientation of the bridge as you go along
the curve. You'd probably have to do the doglegs freehand though.
 
Let me know if I can help you.
 
Terry Farrell
 
On Nov 1, 2012, at 2:18 PM, Ron Nossaman wrote:
 
> On 11/1/2012 12:40 PM, David Love wrote:
>> I'm putting a new board in a MH piano (AA) and considering trimming 
>> that massive 40 mm wide bridge to something more reasonable like 
>> 33mm.  Has anyone ever done that?  What was your method other than 
>> careful band saw and a lot of sanding?
> 
> Make a new one. You'll even get the chance to make a better length
progression across the breaks.
> Ron N
> 
 
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