M. Gilchriese

SQP Clearance

June 8, 2006

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Overview

• A1-2 inners have been mounted on backbone• An A1-2 outer has been mounted on the backbone with A1-2

inner• A1-2 inners on backbone have been mounted on BPSS• In general, the fit to nominal dimensions is excellent and there

are only two significant modifications that are required– Open up the slots in the fiber guides on the bottom of the OSP and the

top of the ISP to increase clearance for tubes. Might be OK without this but safer to open up

– Tabs on CF bottom piece on ISP nearest IP have 2mm clearance holes but the tapped holes in the mating SLA parts glued to the BPSS are 3mm. Holes have to be opened or slotted from the low Z end.

• There are a few spots in which there is an interference of bolt heads(socket heads) requiring either cutting down the heads, changing to flat heads or some local countersinking.

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Cable Clearance(1)

• Two rows of barrel cables.

• Prototype SLA frame with features at the nominal allowed cable envelope(NOT THE TOTAL ENVELOPE)

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Cable Clearance(2)

• 0.75 mm shim fits comfortably under SLA tab. Pile up at first connector can be made near same as at tab

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Cable Clearance(3)

0.75 mm shim fits under tab at edgeLots of clearance nearer centerSpent 1 min arranging cables, coulddo better with some work, but not much

Tab thickness is 0.75mm here

My conclusion: have 1.5mm clearance to cables

IF CABLES ARE THE SAME AS THESE OR SMALLER

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Gaining Clearance at PP0

• To increase the clearance in the PP0 region for cables requires a number of modifications that are described in the subsequent slides.

• The overview is the following– The ISP is moved radially inward, tilted in the PP0 region

– The tubes are moved radially inward, tilted in the PP0 region

– The OSP can then be moved radially inward, tilted in the PP0 region

• The maximum additional clearance that can be obtained in this way is estimated to be 1.5-2mm

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ISP Modifications(1)

Reduce thickness of these tabs by 1.5mm. Chamfer edges

Cut slot for 3mm clearance

Mill tab and CF back from edge by about 1.25 mm to clear SLA

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ISP Modifications(2)

Put 1mm shim here between SLA and CF panel

Cut 3/16” slots here and bring height of web to 5.75mm. All locations

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ISP Modifications(3)

Coral shim represent opto heat spreader.Add additional 1.25mm shim between heatspreader and PP0(preferred) or remake heat spreaders

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OSP Modifications(1)

Increase opening in SLA parts glued to longeron by machining existing parts or remaking(preferred) by 1mm in all tube locations

Glue on 1/32” aluminum splints here to improve strength along entire length

Remake or cut down cap pieces by 1mm Cut 3/16” slots here and bring height of web to 5.75mm. All locations

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Backbone Modification(1)

Face down aluminum surface by 1.5-2mm

Face down tabs by 1.5-2mm

Cut down ground tree piece by 1.5-2mm

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Cost and Schedule Implications

• We have accumulated delays already, partly from issues having nothing to do with clearance and partly from having to address this clearance issue. Roughly 1 month

• If we go ahead with modifications to increase clearance, roughly another month of delay, pushing delivery of first production unit to end of July at the earliest.

• This delay likely propagates and puts the service panels on or very near the critical path with the current pixel schedule.

• Extra material and manpower costs are very roughly in the $50K range, is my estimate, assuming we allow the schedule to slide. We could add manpower to improve the schedule at a cost of roughly $10K per month but not obviously recover all of the delay.