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measuring action ratios

  • 1.  measuring action ratios

    Posted 01-15-2013 21:24 
    From "Joseph Garrett" <joegarrett@earthlink.net>

David L said: 
"When analyzing actions I've used both the gauge for measuring key travel
versus hammer travel as well as the actual measuring and multiplying out the
three separate lever arms."

David,
What gauge are you referring to?
Joe 


Joe Garrett, R.P.T.
Captain of the Tool Police
Squares R I


  • 2.  measuring action ratios

    Registered Piano Technician
    Posted 01-15-2013 22:13 
    From "David Love" <davidlovepianos@comcast.net>

A simple block of wood with an extension (mine is a machine screw) that lays
across the keys and  that depresses a key exactly 6 mm whereby you then
measure the amount of hammer travel and divide that by six to give the
action ratio.  It's been posted several times on the list by Dale Erwin and
others.  I'll post some pictures if I can find one.

David Love
www.davidlovepianos.com



    
                                                
    
					
                                                    

        
                                                
				
    
                                                
    
                                                    
                                                        
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  • 3.  measuring action ratios

    Registered Piano Technician
    Posted 01-15-2013 22:20 
    From "David Love" <davidlovepianos@comcast.net>

Here are two photos.


    
                                                
    
					
                                                    

                
    
                    
    
                        
                        
                    
    
                
    
        
                                                
				
    
                                                
    
                                                    
                                                        
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  • 4.  measuring action ratios

    Registered Piano Technician
    Posted 01-15-2013 22:57 
    From Dale Erwin <erwinspiano@aol.com>

Another picture of the action ratio gauge and an instruction sheet


Dale Erwin R.P.T.
Erwin's Piano Restoration Inc.


 
  






    
                                                
    
					
                                                    

                
    
                    
    
                        
                        
                    
    
                
    
                    
    
                
    
                    
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                                    Hammers-Action Ratio instructions.doc
                                      
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  • 5.  measuring action ratios

    Posted 01-15-2013 23:39 
    From "Joseph Garrett" <joegarrett@earthlink.net>

A simple block of wood with an extension (mine is a machine screw) that lays
across the keys and that depresses a key exactly 6 mm whereby you then
measure the amount of hammer travel and divide that by six to give the
action ratio. It's been posted several times on the list by Dale Erwin and
others. I'll post some pictures if I can find one.
 
David,
Ah, yes. I do recall that now. BTW, thanks for the pics. 
Not sure why it's 6 mm, tho. Why not 5 mm, which is 1/2 of most key dips,
(well sorta<G)
Best,
Joe


Joe Garrett, R.P.T.
Captain of the Tool Police
Squares R I


  • 6.  measuring action ratios

    Registered Piano Technician
    Posted 01-15-2013 23:46 
    From "David Love" <davidlovepianos@comcast.net>

The longer it is the less the margin of error in measuring. But at a certain
point the jack tender hits the let-off button and the hammer travel starts
to change. 

David Love
www.davidlovepianos.com



    
                                                
    
					
                                                    

        
                                                
				
    
                                                
    
                                                    
                                                        
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  • 7.  measuring action ratios

    Registered Piano Technician
    Posted 01-16-2013 06:02 
    From Ed Foote <a440a@aol.com>

>>A simple block of wood with an extension (mine is a machine screw) 
that laysacross the keys and that depresses a key exactly 6 mm whereby 
you then measure the amount of hammer travel and divide that by six to 
give theaction ratio.<> Not sure why it's 6 mm, tho. Why not 5 mm, 
which is 1/2 of most key dips <<

Greetings,
    I like the 6 mm for its ease of reference. I use a jig like Davids, 
and I place a needle through some unused part of the hammer felt so 
that I can measure its rise against a scale as closely as my nearest 
pair of reading glasses lets me.
       It it goes up 36, its a 6:1, 30mm and its a 5:1, all points in 
between are fairly easy to approximate, i.e. 33 mm would be a 5.5:1,
     If anybody takes the time to be really careful, the ratio can be 
seen to change between the first 4 mm of key travel, and the last 4 mm. 
At least, I have.  I think it gives a good indication of how to 
optimally arrange the congruence of the capstan's arc with the 
whippen's.
regards,



Ed Foote RPT
http://www.piano-tuners.org/edfoote/well_tempered_piano.html


  • 8.  measuring action ratios

    Registered Piano Technician
    Posted 01-16-2013 08:35 
    From Dale Erwin <erwinspiano@aol.com>

The action ratio gauge I make for the trade has a pre-printed scale on the back for ease of reference. See attachment.
6 mm isn't just for ease of reference.It cover a wide swath of the keystroke and somewhere between 7 & 8 mm of key travel the l.o. button comes into play. 


 David. Another thing to try is remove the drop screw and turn the L.O. button all the way up. Now take a 10 mm sample or a full keydip/travels worth of hammer movement and see if it changes your outcome.


Dale Erwin R.P.T.




   >>A simple block of wood with an extension (mine is a machine screw) 
that laysacross the keys and that depresses a key exactly 6 mm whereby 
you then measure the amount of hammer travel and divide that by six to 
give theaction ratio.<> Not sure why it's 6 mm, tho. Why not 5 mm, 
which is 1/2 of most key dips <<

Greetings,
    I like the 6 mm for its ease of reference. I use a jig like Davids, 
and I place a needle through some unused part of the hammer felt so 
that I can measure its rise against a scale as closely as my nearest 
pair of reading glasses lets me.
       It it goes up 36, its a 6:1, 30mm and its a 5:1, all points in 
between are fairly easy to approximate, i.e. 33 mm would be a 5.5:1,
     If anybody takes the time to be really careful, the ratio can be 
seen to change between the first 4 mm of key travel, and the last 4 mm. 
At least, I have.  I think it gives a good indication of how to 
optimally arrange the congruence of the capstan's arc with the 
whippen's.
regards,



Ed Foote RPT
http://www.piano-tuners.org/edfoote/well_tempered_piano.html


  • 9.  measuring action ratios

    Registered Piano Technician
    Posted 01-16-2013 08:21
      |   view attached 
    From Dale Erwin <erwinspiano@aol.com>

Dale Erwin R.P.T.
Erwin's Piano Restoration Inc.
 Mason & Hamlin/Steinway/U.S. pianos
www.Erwinspiano.com
Phone: 209-577-8397

 
  






    
                                                
    
					
                                                    

                
    
                    
    
                        
                        
                    
    
                
    
        
                                                
				
    
                                                
    
                                                    
                                                        
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  • 10.  measuring action ratios

    Posted 01-16-2013 16:38 
    From "Joseph Garrett" <joegarrett@earthlink.net>

Thanks to all with the pics of gauges, etc. Now, to my main question: Once
you have done this bit with the gauge and the math, and you have this ratio
number, .... what do you do with it? Or, to put it another way: what does
the number tell you? Or: Of what worth is this number? Or: what does it all
relate to? Anyone care to give "us" the straight poop?<G>
Regards,
Joe


Joe Garrett, R.P.T.
Captain of the Tool Police
Squares R I


  • 11.  measuring action ratios

    Registered Piano Technician
    Posted 01-16-2013 18:21 
    From Dale Erwin <erwinspiano@aol.com>

Hi Joe
 I'm sure the archive are filled with our banter about this but here goes. 
 A 6 to 1 ratio means for every mm of key movement the hammer moves a corresponding amount. SO lets say 6 mm of key movement equals 36 mm of hammer movement. That's the 6 to 1 were talking about. What one actually measures could be whatever the action says. In general the  ratios we find and are in the desirable range are between 5 to 1 and 6 to 1
Many action systems used a 6 to one ratio.ie Steinway for a century at least. What this means is that the system will only tolerate light weight hammers, and the regulation will require a shallow dip(,,370- .375/10 mm at the pin)  and a long blow distance.(1 7/8th /48 mm)If heavy hammers are applied to a system design at 6 to 1 the touch will become heavy. Installing leads to compensate only makes matters worse with increased inertia. Moving the knuckle from 15.75 to 16.5 or 17 will lower the ration. This allows for a bit more hammer weight to be carried with less leading and less inertia. The regulation will need to change as well. Shorter blow & a longer dip/key travel.
In many cases simply moving the knuckle will not yied my desired ration of 5.5. The next move is moving the capstan towards the balance rail to lower the ratio further.
 I'm sure others can elaborate and explain this better and more thoroughly and it can be more complex as David is pointing out. but....
  I think you get the idea.
Dale



Dale Erwin R.P.T.
Erwin's Piano Restoration Inc.
 Mason & Hamlin/Steinway/U.S. pianos
www.Erwinspiano.com
Phone: 209-577-8397

 
  






    
                                                
    
					
                                                    

        
                                                
				
    
                                                
    
                                                    
                                                        
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  • 12.  measuring action ratios

    Registered Piano Technician
    Posted 01-16-2013 20:07 
    From "David Love" <davidlovepianos@comcast.net>

I use the number in combination with other formulas to determine an actual
strike weight curve target, what balance weight that will yield with what
front weight.   You can also use the number to determine how the action will
regulate, with what combination of dip and blow given standard let-off and
aftertouch.  You can also use the number to determine the strikeweight in
order to target the general level of inertia in the entire system (this is
what Darrell Fandrich and John Rhodes are presenting).   You also need the
number to determine what and how much to change in order to achieve the
action ratio you want if it's not right.  It's essential for accurately
diagnosing problem actions and how to fix them or modifying older actions
(if you decide to do that).  

 

In a nutshell:

 

Lower ratios will accommodate heavier strikeweights but will regulate with
longer dip and blow (or both).

 

Higher ratios will require lower strikeweights and will regulate with
shorter dip and blow (or both).  

 

Without knowing the action ratio you are really forced to do things either
by experimenting or simply based on past experience.  I find it an essential
number to have.  

 

David Love

www.davidlovepianos.com

 


    
                                                
    
					
                                                    

        
                                                
				
    
                                                
    
                                                    
                                                        
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  • 13.  measuring action ratios

    Registered Piano Technician
    Posted 01-16-2013 20:43 
    From Ed Foote <a440a@aol.com>

 
In a nutshell:
 Lower ratios will accommodate heavier strikeweights but will regulate 
with longer dip and blow (or both).
 Higher ratios will require lower strikeweights and will regulate with 
shorter dip and blow (or both). 
 

Greetings,
    To my terminology, the lower ratio will regulate with deeper dip 
and/or shorter blow,
The high ratio will often call for the shorter dip and/or longer blow. 
 

Ed Foote RPT
http://www.piano-tuners.org/edfoote/well_tempered_piano.html


  • 14.  measuring action ratios

    Registered Piano Technician
    Posted 01-16-2013 20:48 
    From David Love <davidlovepianos@comcast.net>

Thanks for the correction. I misstated that in my haste.

David Love
www.davidlovepianos.com
415.407.8320


Ed Foote <a440a@aol.com> wrote:

>
> 
>In a nutshell:
> Lower ratios will accommodate heavier strikeweights but will regulate 
>with longer dip and blow (or both).
> Higher ratios will require lower strikeweights and will regulate with 
>shorter dip and blow (or both). 
> 
>
>Greetings,
>    To my terminology, the lower ratio will regulate with deeper dip 
>and/or shorter blow,
>The high ratio will often call for the shorter dip and/or longer blow. 
> 
>
>Ed Foote RPT
>http://www.piano-tuners.org/edfoote/well_tempered_piano.html
>