1890s WNG Action Geometry

[David Love]

If the capstan is too low then cut a short dowel  (the width or less of the
key) of the right diameter to approximate the desired height of the capstan.
Lay some double stick tape on the key stick where the capstan will go so
that you can roll the dowel back and forth and it will stay put.  Then
position the dowel where you think it should go on a key with known front
weight (say 80 - 85% of maximum for that note) and your likely strike weight
given the hammer set you are using.  Move the dowel/capstan around until you
achieve the balance weight you want.  Then mark and measure the position
using Stanwood KR system.  With the little stand it's more important that
you position it consistently.  I line up the front of the key with the edge
of the 90 degree holder which puts the little roller just behind the
front-about where your finger is likely to be.  To mark the capstan position
for drilling I use a jiffy lead trimmed to 10 grams with the screw hole
centered.  Lay the lead on the key surface and move it slowly in one
direction in very small increments until the scale just turns over to the
number you are targeting.  You will notice that the lead will move a fair
distance without the scale changing so you want to be sure you are at the
point where the number just turns to insure accuracy between keys.  Take a
thin transfer punch and insert it down through the hole in the jiffy lead to
mark your capstan drilling position.  Mark the beginning and end key of each
section and then scribe a line with a razor blade.  Check to see that your
lines are contiguous.  Double check and then check it again.  Plugging and
redrilling after plugging and redrilling is really a drag.   

 

Assuming that you are using a 17 mm knuckle I would guess that a Stanwood KR
of about .51 or .52 would be about right especially considering the capstan
is moving away from the wippen flange which will also contribute to a lower
overall ratio.  At least that's where I would start.  It is very likely that
.48 KR will be too low.  On a Steinway that KR would normally match up with
a 16 mm knuckle.  

 

David Love
davidlovepianos at comcast.net
www.davidlovepianos.com 

 

Original message
From: Farrell 
To: "Pianotech List" 
Received: 7/18/2006 5:03:27 PM
Subject: Re: 1890s WNG Action Geometry

Yes, 4.9, Stanwood. Linear measurements suggest 4.8 (man, you're right on
target!). I agree with you - I'm too far forward with the capstan. I'll be
trying a location that simple mathimatical interpolation would suggest to
yield about 5.5/Stanwood.

 

Let's see - on one note, the original location was R = 6.24/Stanwood and an
8 mm move yields R = 4.92/Stanwood. So if I target R = 5.5/Stanwood I should
move the capstan 4.5 mm forward from the original location.

 

On the other note, the original location was R = 6.24/Stanwood and an 11.5
mm move yields R = 4.64/Stanwood. So if I target R = 5.5/Stanwood I should
move the capstan 5.3 mm forward from the original location.

 

So I guess my next try should be with about a 5 mm move forward from the
original location. And of course, the increase in wippen heel height will be
smaller as I adjust that to have the heel/capstan interface on the magic
line at half-blow.

 

I'll give that a try on a few notes and fully regulate them - that'll give
me something specific to talk about then. Thanks for your (and all others!)
input.

 

Terry Farrell

----- Original Message ----- 


 

Is that a Stanwood 4.9 ratio?   If so, I think that's a bit low and you
might compromise the regulation some.  Remember that as you move the capstan
forward on the key you also benefit from the move away from the flange in
the 2nd class wippen lever.  I don't like to get a ratio lower than 5.5
(Stanwood) which should allow you a fair amount of leeway with hammers and
front weights to achieve something between 36 and 40 BW.  My usual target is
37.  If you calculate the ratio via linear measurements, the number will be
bit lower than with Stanwood measurements.  

 

Otherwise, capstan movements are pretty common on action I work on.
Relocating or changing the height of wippen heels is not uncommon either.

 

David Love

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