For more extensive data on John Lahr's seismograph check out his web site. John is attempting to put together a version using locally available accessories (Radio Shack), and using the lowest cost items he can find. Click here for the latest information....click on the faults word and on the new page scroll down to the PSN-Golden page.
 

990521-062c
This is a view of John Lahr's horizontal boom/mast pivot arrangement.  Bascially a wire is inserted into the middle of the boom end and locked in.  From there, the wire goes through the mast via a hole drilled in it.  The wire continues on to and through the shown brass ring, via a small hole, and is locked down by the wire wrapping around the screw on the right hand side of the brass ring.  This is basically the same method as used in the Sprengnether horizontal behind it in the lower photo.  This method averts alot of friction problems where knife edges etc., are involved.
 

990521-063c
A view of a 1950's Sprengnether horizontal seismometer.   It contains two coils, one for damping and one for pickup.
 

990521-064c
Another view of John Lahr's horizontal seismometer and its boom/mast pivot.  Only by very astute observation can one make out the wire crossing between the mast and the inside back of the brass ring.  Johns variation of pivot arrangement is alot simpler than the Sprengnether in comparison, and I would recommend this approach, if possible.  Very well done John.
 
 

990521-065c
A view of John Lahr's mast and suspension wire pivot.  It is a combination of bending and welding for the frame.  The 3 rods contribute to the stability.  The brass rod is a noteworthy approach to supporting the wires associated with suspending the mass/boom.
 

990521-066c
Here is David Latsch with his Sprengnether seismoscope.  Apparently David picked it up a gun auction which also contained a wide variety of other material.  The seismoscope appears in prime condition and is certainly a part of history in strong motion instrumentation.

 RETURN TO MAIN INDEX