[CAUT] Touchweight, etc.

[Fred Sturm]

On 8/1/05 4:16 PM, "David Love" <davidlovepianos@comcast.net> wrote:

> If you are trying to make a decision about whether the geometry is correct
> and whether a parts swap or capstan move is needed, a quick survey a several
> notes with BW, FW and SW will give you a good indication whether or not you
> have a problem.  You don't really need to write it down.  You can calculate
> BW in your head as you go.  Write it on the keystick.  Then check FWs on
> those notes to see if you have room to add lead.  Check SWs to see what kind
> of zone you're in.  Six to eight notes will give you a good indication right
> away.  You might address friction issues on the notes you are surveying (a
> sample, not the whole keyboard) if you feel that accuracy might be
> compromised.  But I would start there.  If you see on those notes that there
> is a friction problem and solving that problem addresses the weight issue
> then you can go ahead.  If you discover that even with minimal friction you
> still have a BW problem then you need to look elsewhere: strike weight,
> leverage, etc..  I think this way is more efficient in terms of getting to a
> conclusion quickly.  Balance weights won't be that much different with
> friction addressed, not enough to mask a real geometry problem anyway.
> 
> David Love
> davidlovepianos@comcast.net
Hi David,
    Yes, you are right. That sampling method can often get you good
information fairly quickly and efficiently. OTOH, I find that Jim Ellis'
point about going through all the basics is very, very well taken. I don't
like to jump to any conclusions based merely on touchweight measurements.
They say a lot, but only within a whole picture. And often one needs to
clear out a lot of cobwebs to see clearly. It is often more efficient to run
through a number of basic steps before getting out any weights.
    But the main point I wanted to make (well, to reinforce the point Jim
Ellis was making) had to do with key friction, which is often overlooked if
you just rely on the usual, rather crude methods of measuring it. The keys
on most grands are leaded heavily enough that they can appear quite free
while having a large amount of bushing or BR hole friction, unless you do
careful diagnosis.
     BTW, to check for BR hole friction, support the front of the key while
slowly allowing it to slide down the pin (lowering the front of the key as
it slides, feeling the slide. Support it with the tip of a finger, lightly).
Let it be the weight of the back half of the key that causes the key to fall
against the friction of the pin against the hole (then adding the balance
bushing friction when it comes into play). I'm sure most folks on this list
know this, but in case anyone doesn't, it's a good technique to learn.
Regards,
Fred Sturm
University of New Mexico