Low Inertia

[David Love]

It's only logical that weight and distance ratios are related.  You can't
change the weight ratio without creating the need to alter regulation specs.
While problem actions we're talking about that have excess lead have, by
definition, a mismatch between ratio and hammer or strike weights, they also
generally regulate with too shallow key dip (<10 mm), at least by modern
standards.  Changing the capstan or knuckle position to improve the ratio to
strike weight relationship will entail increasing the dip but that's usually
a good thing, or at least a perfectly acceptable thing.  If you want the
action to regulate by older standards with shallower key dip you will need
to use very light hammers to go with a higher action ratio (or compromise
the blow distance).

One thing that would be nice would be to establish the relationship between
the Stanwood weight ratio and the distance ratio (since they don't currently
match) so that regulation specs could be targeted using weight ratio as the
standard.  However, since both numbers are easy to calculate it doesn't
present that much of a problem.  

David Love
davidlovepianos at comcast.net 
www.davidlovepianos.com

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Jude Reveley/Absolute Piano
Sent: Monday, October 06, 2008 5:17 AM
To: Pianotech List
Subject: Re: Low Inertia

It is, however, possible to design to a certain action ratio, or maintain 
one, without playing hilly nilly with the regulation specs (specifically 
aftertouch). This will generally require a new balancerail made to a new 
height and location in order to maintain the half stroke for any given set 
of parts. The amount of keyleading will still be particularly dependent on 
the action ratio and hammer weight.

I'm in the process of conducting experiments that test the results of front 
lever arm changes in terms of front weight. David Stanwood has also made the

suggestion to compare weight ratio to distance ratio. I'm hoping to have 
some interesting data in the next few years to share. This making a living 
business is a real drag, especially in this gloom and doom economy; and it 
keeps interfering with my artistic and scientific experiments. ZOUNDS!!!

Jude Reveley, RPT
Absolute Piano Restoration, LLC
Lowell, Massachusetts
(978) 323-4545



> David Love wrote:
>> As one who routinely redesigns actions I'm not sure I would agree that 
>> key
>> lead doesn't play a role in inertial feel of the downstroke.  While I 
>> can't
>> provide the math I can say that I have on several occasions taken actions
>> that were balanced but where the action geometry had left them with
>> excessive key leading.  With a simple move of the capstan the removal of
>> lead, rebalancing the action back to the same balance weight the action
>> "feels" considerably different, less "inertial" as it were.
>
> Yes, which changed the action ratio.
> Ron N
>
>