To do any kind of survey at all you need many impacts so it is hard to imagine a gadget that beats a brute swinging a sledge for portability and multiple strikes. 

A couple of years ago I was sitting in the St Louis airport and noticed a slow vibration of my seat that almost felt like an earthquake. Looking out the window I saw that they were breaking up a runway to replace it. There was a machine that lifted a huge weight and dropped it on the concrete. It would slowly move along dropping the weight every six inches or so. I was a couple of hundred feed away and could still feel it. The machine was breaking up reinforced concrete about 2 feet thick.
That would have made one heck of a survey! :)

Jim Hannon


---------- Original Message ----------------------------------
From: "Doug Crice" 
Reply-To: psn-l@..............
Date:  Thu, 21 Jul 2005 16:47:11 -0700

>A sledgehammer is operated by swinging it through about a 250 degree arc,
>presumably by a muscular associate.  If you were to replace it with a weight
>drop, you would need to drop it many meters to approximate this amount of
>energy. Thus, your weight needs to be accelerated somehow.  There are units
>that attach to vehicles with large rubber bands.  They are cocked by
>electric or hydraulic devices. See photos on
>http://www.giscogeo.com/pages/giscosei.html 
>
> 
>
>We would like to make a significant improvement in energy output. You could
>make a better hammer and  plate, but probably not twice as good.
>
> 
>
> I have considered flywheel operated devices. You could spin up a flywheel
>with a battery operated drill and then couple the energy into the ground
>somehow, though there are strange forces going in strange directions when
>you suddenly stop a spinning flywheel.
>
> 
>
>Doug Crice          http://www.geostuff.com
>
>Wireless Seismic            http://www.wirelessSeismic.com
>
>12996 Somerset Drive                phone 1-530-274-4445
>
>Grass Valley,  CA  95945  USA    fax 1-530-274-4446
>

--
Jim Hannon
http://www.fmtcs.com/web/jmhannon/
42,11.90N,91,39.26W
WB0TXL
--

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