[pianotech] Action ration measuring

[David Love]

Using your method (if I understood it correctly) I get the following on my
action model.  The measurement of dip to hammer travel yields 37/6 or 6.16.
Interestingly, your method of measuring the levers yields a lower AR than my
method (measuring the key to the end and the wippen to the jack center pin)
yet moving the dip measurement 20 mm in from the end of the key will, of
course, produce a higher action ratio than mine measuring at the end of the
key.    

 

On my model the best correlation between levers and displacement (for lack
of a better term) is measuring to the end of the for the key in (along the
bottom of the key as you do) and measuring the wippen out to the jack center
pin as I posted earlier. Perhaps these things are action specific, though
it's hard to imagine why.  Anyway, on my action model Ron's method yields:

 


Key

240

128

	0.53

		

Wippen

63

83

	1.32

	Action Ratio


Shank

17

127

	7.47

	5.25

 

Displacement: 37/6 = 6.16.

 

 

The graphics, btw, are because I was copying from my spread sheet.  Don't
know what this will look like when it gets transposed back to plain text.  

 

 

David Love

www.davidlovepianos.com

 

 

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Ron Nossaman
Sent: Friday, September 21, 2012 8:44 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] Action ration measuring

 

On 9/21/2012 8:21 PM, David Love wrote:

> Thanks Ron.  Question.  How did the jack knuckle contact point that 

> you used compare to the jack center pin?  Were they close?

 

Nowhere near. Center pin spread was 99mm, where what I used was 82. I see I
screwed up the description of wipout. It's a point on the wip beam,
perpendicular to the point of knuckle contact, not level. My apologies.

 

It always annoyed me that the cumulative leverage of the presumed moment
arms matched so poorly with Dale's 6mm in/out direct measurement. 

Something's wrong, and I'll take direct first. So this approach is based on
perpendiculars to direction of travel. I know, it's rotational, but the
rotational stuff is more suited to scholarly smoke generation and
"dissembly" than practical math, because nothing rotates all that far. 

The hammer out is the exception, but then hammer mass is a really big part
of the system, as I've tried to describe many times to the key lead
removers. It seemed like a reasonable thing at the time. The surprise is how
well it matched direct proportional measurement. I'd be interested in how
this works on other actions and models. If you'd run it through yours and
see how it matches, I'd like to see the numbers. This may be totally out to
lunch, but it clicked pretty well with my model.

 

Ron N

 

 

> David Love

>  <http://www.davidlovepianos.com> www.davidlovepianos.com

> 

> 

> 

> 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

> 

> 

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