[pianotech] Action ration measuring

[Ron Nossaman]

On 9/19/2012 9:29 PM, David Love wrote:
> I’m glad this was reposted on this list as I’ve tried to respond to
> the other list via email with no success.  I use the following
> guidelines for measure action ratios.  Different people use different
> methods, I find this one to be the most accurate and meaningful.
>
> This is the beginning of addressing the other question which appeared
> on that other list but which I was unable to respond to with some
> hoop jumping. This had to do with different ratios between sharps and
>  naturals.  The bigger question is what is the overall ratio of the
> system and the second question would be what are the hammer weights
> (or strike weights if you prefer) that will give an indication of
> whether the match between leverage and hammer weight was correct.
> The issue of different ratios for sharps and naturals is a non issue,
> in my opinion. I agree with Nick G. that concern about the magic line
> is overrated.
>
> Once the action ratio is known then with a combination of various
> other criteria, the hammer weight or strike weight can be optimized
> always (as it should with the action ratio) keeping in mind the
> implication for regulation specs.
>
> Sorry I don’t have a picture.
>
> Ea = is the actuating segment of the lever
>
> Ra = is the reacting segment of the lever
>
> -Key Ea is measured from front of key to center of balance pin at
> punchings measured along the bottom of the key.
>
> -Key Ra is measured from center of balance pin to perpendicular line
>  which passes through center of capstan top measured along the bottom
> of the key.
>
> -Wippen Ea is measured from the wippen center pin to a line
> perpendicular to the contact point of the wippen heel/capstan contact
>  point measure along a   line between the wippen flange center pin
> and the jack center pin.
>
> -Wippen Ra is measured from the wippen center pin to the jack center
> pin.
>
> -Shank Ea is measured from the hammer flange center pin to the center
> of the knuckle core measured along the shank.
>
> -Shank Ra is measured from the hammer flange center pin to the center
> of the hammer molding measured along the shank.
>
> Calculate the ratio of each lever according to following example
> RA/EA. The action ratio will be a product of the ratio of the three
> levers.  In this case .49 * 1.59* 7.47 = 5.79


Keeping the measured levers close to parallel with one another, and the 
resulting force close to perpendicular to the levers -
Try

Key in: 20mm from front, along bottom to balance pin center
Key out: balance pin center, along bottom to point below capstan 
position, perpendicular to key
Wip in: center pin, parallel to wip beam to perpendicular line to 
capstan contact point
Wip out: center pin, parallel to wip beam to perpendicular line to 
knuckle contact point
Hammer in: knuckle core center, parallel to shank to center pin
Hammer out: center pin to roughly center of mass of hammer

With my old Teflon centered, felt knuckled Steinweigh action model, I 
get - sorry, no pretty formatting???

Key In - bottom 20mm from end to bottom balance		220
Key Out - bottom balance to bottom capstan position	114
KeyRatio	1.93
Wip In - capstan pos, level to flange center pin	65
Wip Out - center pin level to knuckle contact point	82
WipRatio	1.26
Hammer In - knuckle core to center pin			16
Hammer Out - center pin to center of hammer mass	130
ShankRatio	8.13
TotalRatio Distance Leverage	5.31
	
	
Key Down at pin	6
Hammer Rise	32
Action Ratio	5.33

Ron N