B. Bland, J.^3 (Bartlett, Garcia, and Kissel)

We have cabled the reaction chain of X1 SUS QUAD04 (Which is destined to become H2 SUS ETMY), and measured response. Executive summary: Main Chain looks beautiful, as it did before the lacing. On the reaction chain, Pitch shows a significant increase in stiffness. We should try to adjust the lacing such that we at least get the frequencies equivalent to the after-lacing H2 SUS ITMY measurement.

The whole story:
Attached is a comparison between five measurements of two QUADs: H2 SUS ITMY and X1 SUS QUAD 04, before and after lacing. I chose these measurements because they are most similar in there before vs. after assembly states. Regrettably, the reaction chain between the two are comparing an ITM (thin) and ETM (thick), but by now, we're comfortable with the differences in dynamics between these two species of QUAD. 

The description of each measurement is as follows:
ORANGE (H2SUSITMY, "Before Lacing").

     2011-08-10 measurement of H2 SUS ITMY
     - Metal dummy masses in place. 
     - In the LVEA, on the mechanical test stand 2, suspended from a solid stack.
     - Protected from air currents with a C3 parachute. 
     - No lacing cables in this measurement.
     - No cage stiffening elements are in place

BLACK (H2SUSITMY, "After Lacing 1"). 

     2011-08-15 / 2011-08-12 measurement of H2 SUS ITMY,
     - Metal dummy masses in place. 
     - In the LVEA on the mechanical test stand 2, suspended from a solid stack.
     - Protected from air currents with a C3 parachute. 
     - All lacing cables installed but for the ESD cabling (i.e. UIM, and PUM cables).
     - No cage stiffening elements are in place

MAGENTA (H2SUSITMY, "After Lacing 2"). 

     2011-08-25 measurement of H2 SUS ITMY, 
     - Metal dummy masses in place. 
     - In the LVEA on the mechanical test stand 1, suspended from a locked BSC-ISI.
     - Without the protection of a C3 'chute.
     - It has all lacing cables installed but for the ESD cabling (i.e. UIM, and PUM cables).
     - All stiffening elements are in place, including stiffening sleeve, lower structure side panels, and upper structure cross-braces.

CYAN (X1SUSQUAD04, "Before Lacing"). 

     2011-11-15 measurement of X1 SUS QUAD 04, 
     - Metal dummy masses in place. 
     - In the assembly area of the staging building, suspended from a solid stack.
     - Protected from air currents with a C3 parachute. 
     - It has no lacing cables in this measurement.
     - No cage stiffening elements are in place.

GREEN (X1SUSQUAD04, "After Lacing"). 

     2011-11-19 measurement of X1 SUS QUAD04, 
     - Metal dummy masses in place. 
     - In the assembly area of the staging building, suspended from a solid stack.
     - Protected from air currents with a C3 parachute. 
     - It has all lacing cables installed (i.e. UIM, PUM, and ESD cables).
     - No cage stiffening elements are in place.


Happily, the first six pages of the attached show that the main chains of these suspensions are identical and consistent between all five measurements (except for the DC scaling of Pitch in H2 SUS ITMY, M0 2011-08-15 -- see LHO aLOG 1346 for discussion). 

Further, the reaction chains are reasonably consistent between measurements, in L, T, V, R, and Y. However, we see the reaction chain's Pitch are significantly effected by cabling. This is not terribly surprising a this degree of freedom is most sensitive to stiffness and effective d's, for cabling can change. Though we expect the stiffness to increase, the goal is to have this stiffness increase in a consistent manner, such that the resulting transfer functions are similar enough that one can develop a single control filter. 

We can see that betsy's first attempt at lacing up the reaction chain (i.e. the BLACK, 2011-08-12 measurment) was best, and although the X1SUSQUAD04's lacing is not the worst, it's still significant difference from the best. The obvious physical difference between the best 2011-08-12 H2SUSITMY, and 2011-11-19 X1SUSQUAD04, and  are the ESD cables -- BLACK does not have them, where GREEN does. But because 2011-08-25 H2SUSITMY does not have lacing cables, and is the worst, implies that it's the routing of the cables, not necessarily the ESD cable itself.

Another point to consider -- the measurements show the lowest two pitch modes are effected by the cable routing, where the rest of the modes remain constant in frequency. This implies that it's the routing at the *upper stages* that it most effecting the stiffness. This maybe stating the obvious, because the number of cables between stage jumps decreases as you go down the chain -- more cables = more stiffness. However, it's worth pointing out, such that those routing know to focus on those connections for best results.

We will continue to investigate, and perhaps try to re-arrange the cabling, especially since we have the world's expert on QUAD Suspensions on site for the next few days.