action ratios

[David C. Stanwood]

Hi Ron,

5.5 is the typical SWratio for recent Hamburgs according to our extensive
surveys.  They are very consistent that way.  One doesn't have to be
"pushing it" to regulate 5.5 ratio on a Hamburg Steinway with factory
setup.  The 5.0 ratio I referred to was on a Steinway C 1896 that we
installed TopHigh SW on after testing and listening to the tone and
agreeing that for this piano in this situation TopHigh gave improvement.  I
know it's possible with an efficient geometry and we've achieved success
many times with 5.0 ratios but typically we go for 5.3 - 5.5 ratio specs
and have much less trouble.

I have noticed that if the capstan/heel contact is significantly off the
magic line then it action isn't as efficient and it take more dip to
regulate.  So Ron, I would expect your action to be very efficient since
the jack/knuckle contact point is much closer to the magic line (line of
centers) than conventional setups.  Any data?  What/which ratio do you set
your action up for?

Here is a scatter plot of 5 Hamburg Steinway D's from the early 1990's:

http://www.stanwoodpiano.com/hmbratio.jpg

David Stanwood


>Date: Sun, 3 Nov 2002 01:36:55 +1100
>From: Ron Overs <sec@overspianos.com.au>

>At 2:16 PM -0800 1/11/02, David Love wrote:
>>Just to clarify my position on this a bit, I haven't yet encountered an
>>action where low ratios below 5.5 didn't create regulation compromises that
>>I found undesirable, and there it was pushing it.
>
>Agreed!
>
>>   I was surprised to hear David S. comment that he achieved 10 mm 
>>dip 44.5 blow
>>with an action that measured 5.0.
>
>If I recall his post correctly, I think he was referring to Hamburg 
>Steinways being regulatable with their typical 5.0:1 hammer/key 
>ratios for their largest piano.
>
>>That has given me some pause but doesn't
>>change my own experience.
>
>I have watched a couple of Hamburg techs setting up Ds. Sure they 
>carry a "D" key dip block which measures 9.8 mm, but they actually 
>set the dip at around 10.5 mm from what I have observed. I have found 
>10.25 mm dip to be a practical minimum for such actions with 
>hammer/key ratios as low as 5.0:1.
>
>Terry Farrell's recent experiment, where he calculated hammer/key 
>ratios using leverage analysis and weight analysis, yielded typical 
>results. The higher 'actual' ratio occurs to a greater degree for 
>those actions where the lever contacts are further from the lines of 
>centres. The greater the lever contact distance from the line of 
>centres (particularly with regard to the Jack/roller relationship) 
>the greater will be the difference between the actual figures and 
>that calculated by lever lengths. One therefore should be careful to 
>compare figures between pianos by calculating the hammer/key ratio 
>via the same method when drawing conclusions,  ie. don't measure one 
>piano via weight calculation and use the results to predict the 
>behaviour of another action by measuring it using the leverage 
>calculation method....

>Ron O.