[pianotech] Damper Lever Resistance

[David Love]

Actually, I do use the digital scale platform method.  But thank you, it's a
good idea.  Even with that the amount of resistance as it's felt at the key
will be different depending on where in the damper lever travel you set the
scale as you mentioned.  My goal has always been to set the minimum amount
of weight or resistance required for effective damping (and it doesn't have
to be stone cold, dead, instantaneous damping either).  I just haven't been
able to really determine what that minimum is exactly.  Jon's numbers do
somewhat confirm the place I've gotten to over time and represent a lowering
of the Renner guidelines--fairly substantially in the mid range, in fact.
I'm curious what numbers others use if they have them.  

David Love
www.davidlovepianos.com

From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Joe DeFazio
Sent: Monday, November 08, 2010 12:55 AM
To: pianotech at ptg.org
Subject: Re: [pianotech] Damper Lever Resistance


Hi David,

I also find that the Renner published figures are too high. 

I switched to using the digital scale method (attach a fin and zero out), as
Jon Page suggests.  I find that with the scale, whatever numbers one decides
to target, it is much easier to make the measurement at the exact same point
of lift (corresponding to key dip), bringing about a more consistent
tapering.

If you target and achieve a low value at the very beginning of underlever
lift (if that's where you decide to make your measurement), and remeasure at
the very end of underlever lift, you will, of course find a higher value as
the spring is more compressed.  I know that you already understand that, as
it is at the root of your question about where to measure.  

Although I don't have a specific numerical recommendation for you, I am
responding to recommend the digital scale method instead of a gram
resistance gauge because it is easier to pick a precise moment in lift and
measure at that point consistently.  It is also easier to check and refine
your work;  just slide the scale (with an attached fin) down the row,
lifting each underlever onto the fin sequentially.  You can probably check
each section in under a minute (depending on how fast your digital scale
decides and displays a value).  Not that we're in a hurry to complete the
job, but as is typical in piano regulation, faster and more precise
measurements/decisions promote more circular passes through the regulation
step or sequence, which usually results in a more refined end product.

Joe DeFazio
Pittsburgh