Meredith
  The late STM had a (what I feel ) a good long period vertical design using hardware store materials (with some help from Macmaster Carr). There is an adjusting motor which slides a weight for zeroing. I also use a spiral bimetal spring from a analog themometer to help with daily temperature deflection drifts. I think others have constructed his design. I have been very pleases with the results.
  Barry
  

meredith lamb  wrote:
      James and Dick,
   
  Have always wondered about the "original" two flat spring hinges (pivots) themselves...i.e., just exactly what that material was, i.e., size: thickness, width
  specifically was.  Out of curiosity could you tell me what you have/use now..., or even a hint of what you think you have/use now?  
   
  Gary,
   
  They originally were "sold" to be capable of a 30 second period; the same as the horizontals.  The actual use period "problem", in reality;  is absolutely
  limited to the ground pier setting stability....solid rock under the pier is best, and loose soil is the worst for the frequency of adjustment/s.
   
  Everyone,
   
  Hmmm....I wonder how such a similar geometry setup might work, BUT instead of spring hinges, with replace the two pivots with two boom end
  steel/carbide flats on two mast fixed balls pivots like Chris Chapmans current horizontal uses?  What do you think?  Amateur seismometry could
  really use a better vertical design.  
   
  Take care, Meredith
   
   
  On Mon, Aug 18, 2008 at 8:11 AM, Dick Webb  wrote:
  James,

I am rather late to this thread, but I am running 201 and happen to have a brief publication from Sprengnether on it's theory and how to adjust the unit.  They rooted in their archives and found the article for me about 10 years ago.

Email me separately and I can fax a copy to you if it helps.

Dick Webb




Meredith
  
The late STM had a (what I feel ) a good long period vertical design using hardware store materials (with some help from Macmaster Carr). There is an adjusting motor which slides a weight for zeroing. I also use a spiral bimetal spring from a analog themometer to help with daily temperature deflection drifts. I think others have constructed his design. I have been very pleases with the results.
  
Barry
  


meredith lamb <paleoartifact@.........> wrote:
  
  
  
James and Dick,
  
 
  
Have always wondered about the "original" two flat spring hinges (pivots) themselves...i.e., just exactly what that material was, i.e., size: thickness, width
  
specifically was.  Out of curiosity could you tell me what you have/use now..., or even a hint of
 what you think you have/use now?  
  
 
  
Gary,
  
 
  
They originally were "sold" to be capable of a 30 second period; the same as the horizontals.  The actual use period "problem", in reality;  is absolutely
  
limited to the ground pier setting stability....solid rock under the pier is best, and loose soil is the worst for the frequency of adjustment/s.
  
 
  
Everyone,
  
 
  
Hmmm....I wonder how such a similar geometry setup might work, BUT instead of spring hinges, with replace the two pivots with two boom end
  
steel/carbide flats on two mast fixed balls pivots like Chris Chapmans current horizontal uses?  What do you think?  Amateur seismometry could
  
really use a better vertical design.  
  
 
  
Take care, Meredith