hard pounding

[Bill Ballard]

I've put this on the list before, but it's worth repeating. I once provided
fellow NH Chapter RPT Doug Kirkwood with the vertical information about the
string path (from tuning pin to hitch pin) on notes #51 &52 on a Steinway
B, along with the greatest vertical displacement I could measure at the
strike point of note #52. (The hardest I could get the hammer to knock the
string upwards was 0.049".)

Doug reported to me that the friction barrier at the capo bar was slightly
over 20 lbs.  When the hammer is in contact with string, it momentarily
divides the string into two segments. The elongation at that upwards
displacement of .049" produces a momentary increase in tension in the
segment between the strike point and the capo of 3.8 oz. Looks more like a
toothpick than a crowbar. "Dirty little secret", we curse under our breaths
as we look at our bludgeoned hands.

As far as rendering across the bridge (don't you just love these terms
we've inherited fromthe meat-packing industry!). the vertical portion of
the bridge's friction barrier is very slight due to the slim displacement
produced by downbearing. The horizontal component of the bridge's friction
barrier (from being pulled around a pair of leaing bridge pins) is far more
difficult to calculate with the sort of model I gave Doug. But it can be
inferred with an ETD (although we never got to that).
	1.) Pick a note (any note.)
	2.) Measure starting pitch for both Speaking Length and behind
bridge segments
	3.) With tuning hammer, change tension on the SLength while
plucking in the back length for the
 	  earliest indication of a tension (pitch) change there.
	4.) When tension in the back length changes, freeze the tung hammer
in place, immediately measure
   	   the SLength  ptich.

The change in SLength tension at the moment when you hear the back length
pitch change is  equal to the total friction barrier presented by the
bridge to the string. Whether the test blow can muster more than the  1% it
was capable of regards to capo bar, remains to be demonstrated. Raising the
bridge's total friction barrier up from what we know to be its vertival
component would be the wedging effect of the string being pulled into a
leaning bridge pin. Tending to minimize a test blow's effect on tension
diffentials across the bridge would be the fact that the elongation it
causes is on a segment 8 times longer. (Assuming a strike point of 1/8 the
SLength.)

Comrades (so as to avoid the word "Gentlemen"), start your ETDs.

"Richard Moody" <remoody@easnet.net> wrote:
>Test blows are necessary to learn ear to hand
>coordination of the tuning hammer. Once it is learned fewer and fewer test
>blows are needed, as you say.

The salient aspect of this is to trust one's own feeling about one's skill.
(Speaking in the third person impersonal, of course.)

"David ilvedson" <ilvey@a.crl.com> wrote, 4/10:
> My teacher, Bob Erlandson, taught us that the pin is
>stable when slight pressure up or down produces the same pitch
>change.

That's where it's at. That's why I say it's in the hand on the hammer. Bob
Davis wrote about this a year ago (on Susan Klein's urging). Bumping up and
down from what you hope is a settled tuning pin and string path is a far
better indicator of how close to the relaxed center the pin torsion and
tension differentials across friction barriers are. What can the stiffest
test blow get on note #52 on a Stwy B? 1% of the capo friction barrier.
Does the tuning hammer have a greater mechanical advantage than this? If it
didn't we wouldn't be able to tune pianos at all.

"Richard Moody" <remoody@easnet.net> wrote:
>they should demonstrate instead that the piano indeed has problems as you put
>it in the proper relationship of tuning pin friction but most importantly
>string friction at the pressure points.

Let's clean up that sentance a little, Richard, for the folks back home.
The proper relationship *between* pin firction and string friction. If
string friction is higher that pin friction, there's no way the
"bump-up-bump-down" is going to work. I covered this in 2-3/91 PTJs.
("String Friction and its Coordination with Pin Friction in Tuning
Mechanics".) Similar to a blindfolded person told he has been put next to a
cliff, but not told how many steps away, or whether he is facing it or not.

Bill Ballard, RPT
New Hampshire Chapter, PTG

"We mustn't underestimate our power of teamwork."
 Bob Davis