## PSN-L Email List Message

**
Subject: Re: A spring's constant**

From: "Geoffrey" gmvoeth@...........

Date: Sat, 22 Aug 2009 15:51:13 -0700

There is a company called Century spring
which I believe you can find knowledge about their
springs. It is my personal experience with
extension springs that if they are a simple coil
of a certain diameter wire with a certain diameter
coil it will be fairly linear in ounces per inch
or inch per ounces as the constant so the
formula is linear like y=mx+b as seen
in most algebra books.
Sometimes they have pretension on them
so like they do not extend 10 inches to
get one second of period but 9 because
one inch of tension is already in the spring.
You need to subtract the no weight length
from the weighted length and possibly
add any pretension length. if you
look at overall spring length.
Also I have found the pendulum formula
good for linear springs
Period = 2*Pi*
SQR(INCHESextension/386.0885827averagegravityat sea level)
Which means with any weight which
extends a spring about 10 inches
will give you about one second of period.
Id like to have a 20 foot spring with this idea.
With a one ton weight (2000 lbs Avdp.)
Avodupoise not Troy.
Avi.....Oh Darn Darn Darn I just cant spell.
Thats all I know which isnt much.
Best regards;
geoff
----- Original Message -----
From: "tchannel"
To: "psn"
Sent: Saturday, August 22, 2009 11:07 AM
Subject: A spring's constant
Hi Folks, This question maybe a simple one........Is a spring's constant, its "stiffness" I have a formulas for finding the
constant, but I am unclear what it is.
As an example, I hung a spring, with no addition mass, and I measured how much force is required to pull it 2". Next I add 100g of
weight to the end of the spring, and measure the force it took to move it 2". The force was now different. Easier? Is this the
change in the springs constant?
I did this with several different weights, and using the formula K=mg/x, I noted the different constants. I was surprised that
these numbers were not close, they were not "constant".
On one spring this K decreased as I added weight, On a different spring the K increased as I added weight.
I also would like to a formula to find the frequency of a spring.
Please if you can, would you include an example, showing your math figures? I am not very good at math and the examples help a
lot.
Thanks, Ted
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