Hi Chuck,  I have built both types.   I have notes, pictures, and do's and 
don'ts as I see them.   I can say the folded pendulum was harder for me to 
build, primarily because It was my first and I knew very little about the 
principal.   I think reguarding these two type, their results are about the 
same.   There is more information avail. for the Lehman.  That is one big 
advantage.
Ted
----- Original Message ----- 
From: "Chuck Burch" 
To: 
Sent: Friday, August 31, 2007 9:47 AM
Subject: swinging gate vs. folded pendulum


>
> Being new to the home-built seismograph business I wonder about the
> advantages/disadvantages of the "swinging gate" vs. the folded pendulum 
> designs
> for horizontal component seismometers.  The swinging gate appears to have 
> the
> advantage of simplicity requiring just two pivots while the FP requires 
> eight.
>
> Chuck I. Burch
>
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