Keys and MOI - wipp assist

[Don A. Gilmore]

Most common springs behave in a linear manner.  In other words, the amount
of force they react with when compressed is a ratio of how far they are
compressed.  The general equation is

F = k * x

Where F is the force (lbs, or newtons), x is how far it is
compressed/extended (ft, or meters) and k is its stiffness (lb/ft, or N/m),
which depends on the thickness of wire, the material and the length of the
spring.  k remains constant for any compression/extension (within reason).

For dynamic calculations involving springs you would integrate the above
equation with calculus to get it in terms of energy and get

V = 1/2 * kx^2

Where V is known as the "elastic potential energy" and is in energy units
(joules, or ft-lbs).  If you know how far the spring is compressed and its
stiffness you can calculate how much potential energy it has stored.  An
example of where this would be useful is where you know the kinetic energy
of an object, you can figure how far it will compress a spring when it hits
it.  You can also calculate how much KE an object will have after being
hurled by a cocked spring.

Don A. Gilmore
Mechanical Engineer
Kansas City

----- Original Message ----- 
From: "Don" <pianotuna@accesscomm.ca>
To: "College and University Technicians" <caut@ptg.org>
Sent: Tuesday, January 06, 2004 10:46 AM
Subject: Re: Keys and MOI - wipp assist


> Hi Fred,
>
> I should think that the magnetics suffer from the inverse square law.
> Anyone know of a similar "ratio" for springs?
>
> At 03:22 PM 1/6/2004 -0700, you wrote:
>  Both are fairly
> >static sources of energy (the wipp assist spring de-compresses very
little,
> >hence its available energy remains fairly constant throughout an action
> >event. As does the force of the underkey magnets, since the distance
> >doesn't contract that much).
>
> Regards,
> Don Rose, B.Mus., A.M.U.S., A.MUS., R.P.T.
>
> mailto:pianotuna@accesscomm.ca
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>
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