## PSN-L Email List Message

Subject: Zero Length Spring
From: "Randy" rpratt@.............
Date: Wed, 27 Dec 2006 20:25:26 -0600

```Hi Again,

Thanks for the earlier replies.  I spent a few wonderful days in North =
Dakota for the holiday so have just gotten back to it.  Bob can you =
explain the SeisK in your program?  Is it a derived spring constant for =
the geometric conditions created or a stability factor?  I note that =
negative is always unstable but a negative length spring does not create =
instability.

I still have not answered my original question though.   I have 3 =
examples from Bob's program below.  The first is similar to a spring I =
have currently set up.  The second is a zero length spring with the same =
spring K and attachment point on the boom set to the same period.  The =
third is a softer spring of 0 length.  Given 2 springs and the same =
period, will one operate noticably better at a given period in practice? =
=20

SpringAngle=3D 25, Force=3D 1.3898, Length=3D 0.2247
X and Y -0.0076,0.1079
TorqueUp=3D -0.000339, Down=3D 0.000337
SeisK=3D 0.6622,  Period=3D 1.44=20

SpringAngle=3D 12, Force=3D 2.4595, Length=3D 0.1783
X and Y 0.0216,0.0501
TorqueUp=3D -0.000337, Down=3D 0.000337
SeisK=3D 0.6604,  Period=3D 1.44

SpringAngle=3D 35, Force=3D 1.0685, Length=3D 0.1797
X and Y 0.0488,0.1161
TorqueUp=3D -0.000329, Down=3D 0.000329
SeisK=3D 0.6454,  Period=3D 1.45

Hi Again,

Thanks for the earlier replies.  I =
spent a few=20
wonderful days in North Dakota for the holiday so have just gotten back =
to=20
it.  Bob can you explain the SeisK in your program?  Is it a =
derived=20
spring constant for the geometric conditions created or a stability=20
factor?  I note that negative is always unstable but a negative =
length=20
spring does not create instability.

I still have not answered my original =
question=20
though.   I have 3 examples from Bob's program =
below.  The=20
first is similar to a spring I have currently set up.  The second =
is a zero=20
length spring with the same spring K and attachment point on the boom =
set to the=20
same period.  The third is a softer spring of 0 length.  Given =
2=20
springs and the same period, will one operate noticably better at a =
given=20
period in practice?

SpringAngle=3D 25, Force=3D 1.3898, =
Length=3D 0.2247X=20
and Y -0.0076,0.1079TorqueUp=3D -0.000339, Down=3D =
0.000337SeisK=3D=20
0.6622,  Period=3D 1.44

SpringAngle=3D 12, Force=3D 2.4595, =
Length=3D 0.1783X=20
and Y 0.0216,0.0501TorqueUp=3D -0.000337, Down=3D =
0.000337SeisK=3D=20
0.6604,  Period=3D 1.44

SpringAngle=3D 35, Force=3D 1.0685, =
Length=3D 0.1797X=20
and Y 0.0488,0.1161TorqueUp=3D -0.000329, Down=3D =
0.000329SeisK=3D=20
0.6454,  Period=3D 1.45

Randy
```

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