[pianotech] Force equivalents in different actions

[Gene Nelson]

I have restored an older Knabe - as it was my piano I chose to experiment. 
After stringing I used a few hammers and ended up with Peter Clark's 
Classical West hammers - they are big, dense and cold press - similar to 
Isaac's.
Strike weights are quite heavy - 13.5g at A0 and tapering along a typical 
Stanwood curve for that range.
The action geometry was altered to accommodate and the ratio is quite low 
with 10.3mm dip and 45mm blow. Three and a half leads in the bass and 
tapering to one on the hammer side of the top three. I also like low 
friction so the touchweights are all 52g down and range evenly from 32  to 
38 up from bass to treble. Checking is set at 6.5mm right now - WNG checks 
allow this. It feels and sounds good to me.
After Del's class - spent the day today reducing bearing - especially in the 
bass/lo-tenor and did improve the tone slightly.
I have been lectured about the down side of heavy hammers to include much of 
what you say about the force that hits the string - slower moving from heavy 
and faster moving from light but overall power/force the same - wear and 
tear on bushings etc. I do listen, believe me.
I think that the point about action saturation cannot be excluded as 
certainly everything flexes more with heavy.
The hammer will only accelerate so fast and how would anyone know if you 
were at the saturation point? That would remove anything resembling a linear 
relationship and put an upper limit on force applied to the string.
Maybe WNG shanks can help reduce saturation but that is another story.
And the tone is different. I believe felt resilience plays a roll.
I have also been lectured that heavy in the treble is not good - with 7.5g 
sw at G7 I have great power and clarity - go figure. If the hammer string 
contact is calculated on the high side, it is not muting any pleasing 
harmonics anywhere on the piano. Lowest 4 notes excluded.
Ready to get hammered publicly.
Gene



> Well it may well be apples and oranges.  Part of the reason for my inquiry
> is that I'm giving a presentation soon on choosing replacement hammers. 
> Of
> course there are many criteria and considerations but one, of course, is
> weight.  Let's take Steinway for example, not to pick on them but because
> it's a good illustration.  The original hammer on a Steinway from the 
> 1920's
> was very light in weight. In my view it suited that scale and belly fairly
> well.  It's not unusual for the hammer at note 40 to be on the order of 
> 6.5
> grams.  When looking at hammers offered for replacement on those pianos
> (even by Steinway themselves), it's not unusual to see the them increasing
> in weight by several grams.  Those who have made the mistake of doing so
> without modifying the leverage know the disastrous results in terms of
> touchweight.  So, it's not unusual to change that original 15.5 or 16 mm
> knuckle to a 17 mm knuckle to accommodate.  But how many people, I wonder,
> consider what the increased hammer weight does to the tone when they opt 
> for
> that new hammer.  Judging from what I see, not many, unless people are
> opting to increase weight for a specific tonal reason, i.e. to get more
> power, attack etc..  Even the sticklers for "original Steinway parts" must
> admit that the new hammer (and even more so the bulkier hammers that were
> offered from the 1960's through the 1990's) were substantially heavier,
> produced a very different tonal attack and development, and increased 
> power.
> Now on an old Steinway board that might be ok but it might not, depending 
> on
> the condition of the board and other factors.  Certainly it changes the
> tonal character.  So as a not too random sampling I'm interested to know 
> how
> many people do or don't consider weight of a new hammer in terms of the
> change in tone that it will produce.  Or do you just select the favorite
> hammer of the day and adjust the leverage accordingly (hopefully), 
> assuming
> voicing will take care of any unwanted changes?  Further, does the 
> original
> hammer that Steinway produced for that piano (keeping in mind that the 
> piano
> of that era produced and maintained a somewhat stiffer board than the one
> after they began to diaphragmize) suggest that they were focusing on power
> in their original concept?
>
> David Love
> www.davidlovepianos.com
>
>
> -----Original Message-----
> From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On 
> Behalf
> Of Mike Spalding
> Sent: Wednesday, March 24, 2010 11:32 AM
> To: pianotech at ptg.org
> Subject: Re: [pianotech] Force equivalents in different actions
>
> Some additional thoughts:
>
> 1.  Producing identical sound loudness probably requires equal energy
> transfer from the hammer to the string.  Energy is not equivalent to
> momentum.  Energy is mass times the square of the velocity.
>
> 2.  To ask the question the way it has been phrased, assumes that the
> motion of the key is the same in both A and B.  I think this is
> unlikely, as the inertia seen by the finger at keystick B is
> significantly less than in A, so the same pianist will produce different
> velocity profiles in the two keys.
>
> 3.  A slower heavier hammer transferring the same amount of energy to
> the string will probably have a different dwell time at the string.
> Will that affect how much of the hammer's kinetic energy actually gets
> transferred to the string?  Not  a simple answer, since we're talking
> about energy distributed across a spectrum of partials.  Perhaps you
> could equalize dwell time through voicing.  Perhaps you'd rather make
> them sound as similar to each other as possible through voicing.  In
> either case, it's starting to look a lot like apples and oranges.
>
> Mike
>
>
>