Stanwood "Polar Rule"

[Cy Shuster]

Terry,

See p. 3 here:

http://www.stanwoodpiano.com/seesaw.pdf

D = BW + F

Downweight is balance weight + friction.  With a given downweight and friction, you can have only one balance weight.

D - F = BW

I like the polar rule; it's handy for calculating friction when doing appraisals.

--Cy--
  ----- Original Message ----- 
  From: Farrell 
  To: pianotech at ptg.org 
  Sent: Friday, July 06, 2007 8:59 AM
  Subject: Stanwood "Polar Rule"


  Does anyone use David Stanwood's Polar Rule for calculating BW & FW from DW & UW? I understand well that all this thing does is save you from punching a few numbers into a calculator and writing a couple number down (or doing it in your head - ouch!) - but hey, I find it easy and fun to use and I don't have to punch my calculator (or strain my brain). I bought it many years ago when he first came out with it - I guess I really thought it was something else.

  My question follows - and I am quite perplexed on this one. When using the Polar Rule you first turn the red dial to match up with the DW. Then you turn the center dial to line up the UW on the red dial. Then you simply read off the FW and BW. 

  Great. Easy. Fun. Done.

  Or maybe not...........

  Le's say you have a 50 gram DW and you know that you will regulate friction to a medium amount of let's say 11g. You are stuck with a 39g BW. It can't be anything else if you want 11g of friction (using the Polar Rule). Yet I know that I can increase pinning friction and not affect BW. BW is independent of friction. But the Polar Rule suggests it can't be. This makes no sense to me.

  My question is less about what is the nature of BW, but rather what the %$&* is the deal with this Polar Rule.

  I know someone is going to suggest something that is going to make me feel real stupid for publicly posting this question - likely should have shot it to some expert privately (or likely anyone with basic common sense) - but hey, maybe someone else uses this goofy but handy little gizmo and has wondered the same thing.

  Anyone got an answer? Go ahead, take your shot at me!   :-)

  Terry Farrell
  Farrell Piano

  www.farrellpiano.com
  terry at farrellpiano.com
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