1890s WNG Action Geometry-Capstan boats

[Absolute Piano]

David and all,

In addition, I try to make my "capstan boats'' or markers the same weight as what I will be using. Otherwise, the usual 5-6 grams of capstan weight will throw off your FW by 2-3 grams unless you've already compensated for that. Not clear?

Jude Reveley, RPT
Absolute Piano Restoration, LLC
Boston, Massachusetts
  ----- Original Message ----- 
  From: David Love 
  To: 'Pianotech List' 
  Sent: Tuesday, July 18, 2006 9:51 PM
  Subject: RE: 1890s WNG Action Geometry


  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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