Measure friction weight was: Weighting upright keys question

[David Ilvedson]

Well, hopefully that wasn't pianotek?   It has this hand written weight certification inside...



David Ilvedson, RPT

Pacifica, CA 94044









Original message

From: "Porritt, David" 

To: "Pianotech List" 

Received: 2/18/2008 6:12:53 AM

Subject: RE: Measure friction weight was: Weighting upright keys question





Julia:



Keep in mind that the weights from some suppliers are not accurate.  I bought the little gram weight set from a major supplier and found them all to be heavy (fortunately).  I simply drilled holes in each weight to remove the excess and calibrated each one.  Some of the weights have a lot of holes!  Of course to do this you’ll need a good scale properly calibrated and capable of reading down to at least 0.1 gram.



dp



David M. Porritt, RPT

dporritt at smu.edu



From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Fenton Murray

Sent: Sunday, February 17, 2008 7:49 PM

To: Pianotech List

Subject: Re: Measure friction weight was: Weighting upright keys question



Julia,

To do this work you'll need a set of gram weights. They are for sale at most of the supply houses. With these weights you can place an exact amount on the end of the key, say 50 grams, with the damper pedal depressed (important), see if the key will fall to the point of let off. We are only concerned with the travel of the key from it at rest up position down to the point of let of. The lowest amount that will cause the key to drop (with the damper pedal depressed) is the down weight. Then depress the key to let off and place an amount on the key, the most the key will lift up to it's at rest position is the upwieght, maybe around 25 grams. A little taping on the key bed to get things to move is OK. You need to try some of this before trying to figure it all out. Once you've spent some time with it you'll find it opening doors to a higher level of action work. There is lot's to understand. Read the Stanwood articles in the PTJ, I think they were early '90s. Use the PTJ on CD.

Fenton

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

From: KeyKat88 at aol.com 

To: pianotech at ptg.org 

Sent: Sunday, February 17, 2008 3:22 PM

Subject: Re: Measure friction weight was: Weighting upright keys question



Greetings,



             So how do I start making measurements to see what weight a key(s) neeeds?  How do I measure friction? I am guessing that I should start  by measauring the the foot-lbs (or cm-grams?)  inertia it takes to start the power stroke at the wippen heel/foot. Then I have measured my fricion...right? Then I can do the uw/dw calculations.



Julia 

Reading. PA



In a message dated 2/16/2008 11:27:46 PM Eastern Standard Time, fmurray at cruzio.com writes:

Given a certain friction in the piano we are going to want to set up something like maybe a downweight (dw) of 50 and an upwight (uw) of 25. All numbers in grams. This is assuming a friction of 12.5.













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