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Message ID: 769     Entry time: Tue Dec 27 16:11:07 2011
Author: Frank 
Type: Notes 
Category: Seismic 
Subject: stack TF updated 

updated the stack TF using more accurate numbers for the RTV springs and masses and also updated the proposed TF for the stack using the modified RTV springs (see elog #762) (instead of SS springs). The updated model can be found on the svn.

Drilling the hole in the center of the existing springs reduces k to 19150N/m (RTV615 block, ~35Hz resonance (max value measured ~35Hz, minimum ~33Hz) with 0.396kg mass) from the original k=28900N/m (RTV615 block ~43Hz, resonance with 0.396kg mass). It should also be possible to reduce the number of springs from 8 to 4, at least for the top stack. For the bottom we have to check how much clearance we will have left between the two stack plates if we use softer springs and reduce the amount by a factor of two.

 estimated stack TF using measured RTV spring values

stack_TF.png

Ring-down measurement of modified RTV spring

P1810299.JPG

 

ELOG V3.1.3-