Keys and MOI - wipp assist

[David M. Porritt]

Fred:

I think the "moi" advantage of wippen springs is the ability to eliminate some of the key leads, thereby reducing key inertia.

dave


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David M. Porritt, RPT
Meadows School of the Arts
Southern Methodist University
Dallas, TX 75275


----- Original message ---------------------------------------->
From: Fred Sturm <fssturm@unm.edu>
To: College and University Technicians <caut@ptg.org>
Received: Tue, 06 Jan 2004 07:52:45 -0700
Subject: Re: Keys and MOI - wipp assist

>	In this discussion there have been references to wippen assist springs, 
>but no thorough description of exactly what their effect is, particularly 
>with regard to "perceived moi". This is something that has long puzzled me. 
>With an assist spring, we have stored energy supporting mass, and assisting 
>in its acceleration. The hammer mass (and the rest of the action mass) 
>remains the same, hence its moi remains the same. The leading of the keys 
>is reduced, hence the moi of the key is reduced.
>	I guess my main question is, "Is the moi of the hammer assembly, as 
>perceived from the key, reduced by the engagement of the spring?" Since the 
>stored energy is always present, the energy required to accelerate the 
>hammer assembly mass from the front of the key is always reduced. So does 
>that, in effect, reduce the moi of the hammer assembly mass? Or how does 
>the spring enter into the picture in engineering terms?
>	I can imagine "an elephant" on the end of a hammershank, with an 
>extraordinarily strong wipp spring, and in imagining that, I suspect that 
>the hammer assembly moi will continue to be related mostly to the mass of 
>the hammer even as perceived (blind-folded) from the front of the key, 
>regardless of the assistance of the spring. But I would like to hear some 
>discussion of exactly what a wipp assist spring does to the feel and 
>performance of an action, and why, in engineering terms.
>Regards,
>Fred Sturm
>University of New Mexico


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