Hello Mr. Nordgren,

You speak in a way I might be able to understand.

What I was wondering is that buoyancy can be implemented in ways
which might produce spring like results possibly one might
use a "weak spring (low weight/inches)" with whatever mass
in combination with buoyancy "like a submarine or ship" to
produce extended or lower frequencies using shorter lengths.
simply submerging the mass within a dense liquid may allow
this to happen.

has such a thing ever been tried ?

I saw this research ship which could be flooded
to float like a fising bobber ? it made me think
of other things like this one above.

thanks for your responses.

regards,
geoff

p.s quite a flurry of Equakes in southern california today.
I wonder if Kirsty Ally is doing her aerobics ?
or so ive heard before. 

----- Original Message ----- 
From: "Brett Nordgren" 
To: 
Sent: Wednesday, February 29, 2012 6:36 AM
Subject: Re: Instrumentation


> Geoff,
> 
> You have stated the problem quite clearly.
> 
> A specially designed spring has been the only thing found to work 
> sufficiently well in practice.  What you need is a spring arrangement 
> strong enough to support the mass, but designed so that when the mass 
> moves up and down, the spring changes its lifting force only *very* 
> slightly.  One way of looking at its effect is that such a spring 
> setup makes the mass think that gravity has become very small, 
> behaving something like a rig they used to train the astronauts 
> headed for the moon.
> 
> An early design geometry, the LaCoste configuration, involving a 
> "zero-length" coil spring did exactly that.  But now almost all 
> instruments use a thin "U" shaped leaf spring, like in Sean-Thomas' 
> STM-8.  Magnets have the problem that their force varies quite a lot 
> with temperature and if you make your instrument very sensitive, it 
> will drift out of range with even a small temperature change.  That's 
> a big problem with springs, too, but the effect is maybe 5x 
> smaller.  With the leaf spring, the geometry of its design is 
> critical, with only a few hundredths of an inch change in its length 
> or attachment point making a significant difference in how it behaves.
> 
> The only effective way I know of to deal with the temperature drift 
> is with electronics.  You sense the position of the mass and make a 
> circuit which will apply a gentle force using a coil and magnet to 
> slowly nudge the mass back toward where it should be.  Way more 
> complicated than that, but most modern seismometers use something of 
> the sort.  That approach is usually extended to provide other 
> benefits, too, making the signal distortion smaller and broadening 
> the instrument frequency response while making it more predictable and stable.
> 
> Regards,
> Brett
> 
> At 12:44 AM 2/29/2012, you wrote:
>>Hey Guys,
>>
>>Ive been looking at the pull of gravity
>>and what you need to do to lengthen period.
>>
>>
>>Like here's what seems to be:
>>
>>
>>Given any proper spring extended by whatever mass 10 inches
>>the free period on earth is like 1 second.
>>
>>
>>if the gravity is made less and you use the same spring
>>here is what happens.
>>
>>to extend the spring to 10 inches on the moon
>>you need to increase the mass until the wight
>>will deflect the spring 10 inches. then
>>you get like 1 * sqr( gEarth/gmoon ) or 2.4 seconds.
>>
>>This means to me you need to reduce gravity considerably
>>like 1/25 to 1/100 to get the free periods you are looking for.
>>
>>
>>Does anyone know how to build a circuit based upon this idea.
>>
>>I mean,
>>
>>Like,
>>
>>Magnetic levitation to effectively reduce
>>gravity by 1/25 or 32.17/25 = 1.28 f/(sec^2)
>>
>>I mean in layman terms,
>>
>>How can one reduce the pull of gravity
>>so that gravity effect is like 1.28
>>instead of 32.17 using any practical means
>>known today ?
>>
>>You are playing with forces here
>>which means you will need to
>>take most of the wight off the spring
>>and use a smaller spring coefficient
>>with the very same mass.
>>
>>I have been thinking like
>>buoyancy in whatever OF magnetic field
>>or electrostatic or mechanical
>>advantages ???
>>
>>Any ideas ?
>>
>>I am relatively sure everything has
>>already been tried even tho no one
>>talks about it.
>>
>>Any relevant answer is appreciated.
>>
>>Regards,
>>geoff
> 
> 
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