J. Kissel, C. Vorvick

I've processed the data from last week's first B&K adventure into HAM2 which included the HAUX (a.k.a. HAM Auxiliary Suspensions, a.k.a. IMs or Input Mirrors) (LHO aLOG 39096). 

Recent efforts tightening and torquing the cage bolts to spec (e.g. LHO aLOG 38808) has helped increase the resonance frequencies and Qs of the first bending modes of cage to ~170 Hz in Longitudinal and 220 Hz in Transverse.

These modes are significantly better* than those at L1. 
*Here, by "better" I mean well-defined, high resonance frequencies, and features are similar between suspensions.
The data I use from LLO is the same as posted in LLO aLOG 3948 for IMs 1,2, and 4 from their 2012 vent, and the more recent LLO aLOG 25919 for the problematic IM3 from 2016. 

After discussing with Cheryl, there are several differences that elucidate this difference. 
(1) While LLO has used the "IO" dog clamps of several varieties (D1100640), LHO has used the champhered-ended "SUS" dog clamps (D1100641). These create a more well-defined contact point. 
(2) In addition, the layout of dog clamps around the base of the cage is significantly different; LHO revised the original layout, seeing how unstable the originally prescribed appeared. See table below for comparison of layouts:

Current   Former      Original    Revised
Name      Name        Layout      Layout
                      (LLO)       (LHO)
IM1       SM1         D1200623    T1400742
IM2       PMMT1       D1200625    T1400743
IM3       PMMT2       D1200626    T1400744
IM4       SM2         D1200624    (not revised)

Further confirming the difference -- IM4's clamping configuration does use the IO clamps, in a similar arrangement, and the frequency responses of the cage between H1 and L1 look quite similar -- in Longitudinal, but Transverse remains quite different.

In light of this data, I propose two things:
(1) At the earliest convenience (if there is still such convenience left), we should ECR Cheryl's improvements, implement them at LLO, and update documentation such that India gets similar benefit.

(2) Now that we've stiffened up the resonances, they've become higher Q. We should consider shoving some viton in between the suspension cage, and, say, each of its black-glass cage baffles. It shouldn't need much.