PSN-L Email List Message

Subject: Re: A simpler Shackleford-Gundersen frame
From: Keith Payea kpayea@...........
Date: Sun, 22 Sep 2002 20:59:51 -0700

Hello All:

I took the concrete block and epoxy approach when I built my STM-8 vertical.
I used two layers of 8 x 16 and 8 x 8 pavers to make a base 8 by 24 inches.
The end of the boom is supported on a pair of concrete bricks.  This whole
thing is held together with construction adhesive.  I painted the concrete
with a good white sealer/primer to keep moisture out.  Other parts are
attached by drilling a shallow hole in the concrete and using epoxy to
attach a "T" nut to the concrete.  Then the part is just bolted down.  This
machine has been in operation for almost three years with no problems.  It
is very stable.   I too toyed with the idea of building an SG out of
concrete parts.  My concept was to use a 12" square paver or two for the
base, and then stand three 8 x 16 pavers on end so they look like a "U"
shape when viewed from above.  I never got a chance to try it out.


    Keith Payea

----- Original Message -----
From: "meredithlamb" 
Sent: Sunday, September 22, 2002 8:07 PM
Subject: A simpler Shackleford-Gundersen frame

> Hi all,
> For a "down and dirty & cheap S-G frame":
> A concrete paver and or about 5 ceramic bricks could also
> be used as a S-G "frame" (one could use more bricks laid
> flat of course).  The concrete paver could be the base.  Two
> pairs of bricks end on end atop the paver, with the fifth brick
> being the crossover piece.  Most (U.S.) bricks have 3 holes in
> them, likely two of the outside holes downward could suspend
> the S-G hinges/boom/mass.   Probably a concrete drill
> and using a old threaded tap size, could give the 3 "setcrews"
> action for adjustments....but even here, simple wedges could
> be subsituted.   Epoxy or even cement could be used for glueing
> the thing together.
> One might not even need a "boom", if another brick is used as
> the "mass" two thin spaced magnet wires are likely strong
> enough to support it.  One could adjust the wire lengths for
> the period somewhat.  I use 0.001" thick by 0.0250 wide by
> 1.5" length brass strips as the hinges in my S-G's with a ~ 3
> pound mass as its needed for the normal period and tilt
> sensitivity of a Hall sensor....none have broken yet over
> acouple years or so since installation.
> Most bricks are electrical insulators and that helps.  There
> is probably some iron oxide in some bricks, but I doubt its
> sufficient to have much influence over its mass weight inertia
> versus any introduced magnets.  Probably the lighter in color
> the brick; the less the iron or other magnetic contaminants
> there is.
> Yes; one could attach a coil....or other wires for whatever sensor
> arrangement is desired.  What the heck....its going to be set up in a
> vault or basement anyway and theres NO known "spiffy" seismo
> fashion appearance magazine reporters around (ha) and this
> possible ultimate in simplicity will get you recording alot faster.
> One thing for sure, it will be quite sturdy (and heavy) which
> helps.
> Damping could be via a oil van/tank or a eddy current damping
> add-on on the "paver" base itself.  The damping aspect maybe
> the most time consuming aspect overall.
> Have to admit, I have no such "critter" here though...ha.
> could paint it "professional" white, if its
> appearance is more "critical" your personal ego
> standards....on the other "chrome" paint could
> somewhat mask the true nature of the "critter"....ha.  The
> primer and paint helps prevent water absorption expansion
> and contraction problems around the cement joints...apply
> any paint after a sufficient cementing drying time has expired.
> Take care, Meredith Lamb
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