LIGO Science Education Center Kinetic Pendulum Wall Exhibit Preliminary Design Review

1. LIGO Science Education Center Kinetic Pendulum Wall Exhibit Preliminary Design Review 27 April 2006

2. Project Deliverables • Engineering CAD realization of the Kinetic Exhibit concept, suitable for fabrication and installation, including: • Design of structural supports and interface attachments • Design of moving elements • Design of bearing and axle attachments and supports • Design of magnet attachments and adjustments • Design of a manual interaction mechanism for visitor excitation of the exhibit • Design of a secure, manually-activated locking mechanism to restrain elements and prevent damage under extreme weather conditions • Specification of bearings, magnets, elastomeric bumpers, lubricants, and other special materials and hardware • Specification of surface finishes and material treatments (coatings, anodizing, etc.) • Design of special fixtures or tooling required for installation and continuing operational maintenance (as required) • Supporting analyses of moments, loads and stresses for static, dynamic and wind conditions, including verification of compatibility with the building structural interface • Installation, alignment and commissioning procedures • Cost estimation and value engineering, as required, to maintain final project within allocated budget • Supporting estimates of installation, life cycle, and maintenance costs • Prototype or first-article fabrication and associated qualification testing, if required

3. Complete Exhibit • 120 Pendulums across 100’ • Magnetically coupled

4. Truss Assembly • Design • 12 Trusses across building • Each truss • 10 Pendulums on 10” centers • 3 axle supports • Welded structural steel • 1 Truss per building structure section (8’4”) • Truss feet to be located close to vertical I-beams for strength • Issues • End pendulums are 16” from edge of siding • Pendulum/I-beam spacing/coverage • Attachment method of Trusses to rails TBD

5. Building Interface • Design • Stringers • 2 structural steel channels • Welded to vertical W6x20 I-beams • Issues • Specify and weld stringers prior to painting? • Hanger/gussets for stringers

6. Pendulum Assembly • Design • Pendulum • 4”x6”x.125”x27’ • 6061-T6 Aluminum • Clear anodized • Natural period ~9s • Stiffener plates • 6”x12”x.125” • 6061-T6 Aluminum • Clear anodized • Riveted to pendulum • Issues • Refine stiffener plate dimensions • Vibrations due to bumper impact? • Fabrication procedure for bearing mount

7. Axle and Attachments • Design • Axle • 1.5” Diameter • 99” Long • 17-4 PH H1150 Stainless steel • Supports • 4 Pendulums between supports • 1 Pendulum overhangs each end support • 2”x4”x.125” Wall structural steel tubing • is a candidate • Issues • Axle attachment design • If tubing is selected, welds must be water-tight • Channel does not require water-tight welds

8. Bearings and Magnets • Design • Bearings • Piloted flange bearing • Collet-type shaft connection • Life expectancy >>100 years • Magnets • 2 per pendulum (likely) • Ceramic magnet • 4”x6” Footprint • Attachments • Sheet metal covers • Issues • Bearings • Lubrication/service interval • Cost • Corrosion resistance • Magnets • Thickness to be determined • Adjustability required for final unit?

9. Excitation Mechanism • Design • Excitation plate • Offset from pendulum by flanged tube • Issues • Ropes tangling in pendulum • Add rope guides? • Elastic cords to limit forces? • Limits to abuse by visitors Ropes to ground

10. Locking Mechanism • Design • 12 Locking mechanism assemblies • Rollers contact pendulums • UHMW or similar • Issues • Axle stiffness • Retain desired preload for all pendulums

11. Locked Locking Mechanism Locking mechanism – stored up • Issues • Storage • View obstruction • Deployment • Must push 10 pendulums into position • Manual powered winch • Visible rope or cable Free

12. Locking Mechanism Locking mechanism – stored down • Issues • Storage • View obstruction • Deployment • Must push 10 pendulums into position • Manual powered winch • Visible rope or cable Free Locked

13. Upper Lower Bumpers • Design • Loading-dock type bumper • D-shaped cross-section • Elastomer material • Issues • Upper bumpers extend forward from roof line • Vibration/noise due to pendulum impact • Material selection for damping, weather resistance

14. Analysis - Stress • Pendulum under side wind loading • Model and assumptions • Analyze lower section only and cut in half based on symmetry • Bearing flange rigidly supports thrust load • Pressure due to wind determined using ASCE 7-05 • “Minimum Design Loads for Buildings and Structures” • Yield strength • 40,000 psi • Max stress • 16,300 psi

15. Analysis - Displacement • Pendulum under side wind loading • Model and assumptions • Analyze lower section only and cut in half based on symmetry • Bearing flange rigidly supports thrust load • Pressure due to wind determined using ASCE 7-05 • “Minimum Design Loads for Buildings and Structures” • End deflection • 2.3”

16. Analysis - Stress • Bumper impact scenario • Model and assumptions • Analyze lower section only and cut in half based on symmetry • Wind acts on the pendulum above the pivot only, normal to the front surface • Pendulum accelerates through its entire range of motion • Pendulum impacts the upper bumper at maximum velocity • Bumper absorbs zero energy • Pendulum acts as two simply-supported flexures to momentarily store impact energy • Upper and lower pendulum stiffnesses determined via FEA • Resulting deflections/forces are calculated • Yield strength • 40,000 psi • Max stress • 26,500 psi

17. Impact bearing loads Pendulum weights Analysis - Stress • Axle under bumper impact loading • Model and assumptions • Cut in half at center • Axle supports are rigid • Bearing loads applied • Pendulum weights • Loads due to pendulum impacts • All pendulums impact simultaneously • VERY conservative • Bumper energy absorption will reduce stresses to acceptable level • Yield strength • 126,000 psi • Max stress • 140,000 psi

18. Y Z X Building Loads • Model and assumptions • Loads • Weight of pendulums, supports, etc. • Wind loads - horizontal at 45° • Distribution • Across vertical I-beams at stringer • elevations: 244” and 284” • Rx = -56959 (lbf) • RY = -21158 (lbf) • RZ = 56959 (lbf) • Magnitude R = 83285 (lbf) • Issues • Building compatibility to be verified • by Mckee and Deville

19. Installation Procedure • Design • Truss assembly can be assembled on the ground • Fixture will be made to allow truss assembly to be picked up with extended-boom fork lift • Issues • Fastening method for truss assemblies • Magnet adjustment in field, if necessary

20. Preliminary Cost Estimation • Issues • Bearing selection, materials • Truss fabrication method • Lock-down method • Refined and verified cost estimates on all items

21. Prototype • Design • 5 Pendulums • Sliding stiffeners • Mild steel • Suspended from scaffolding • Adjustments • Pivot position - 12” range • Pendulum spacing • Magnet position, quantity, size • Tests • Response/coupling • Impact vibrations • Bumper performance • Lateral locking friction • Single pendulum fabricated • per “final” design • Issues • Alternative bearing selection • Risks

22. Questions/Issues • How close to the edge of the building do the end pendulums need to be? • Can the pendulum range of motion be asymmetrical? • Verify that the west (4) vertical W6x20 I-beams will not have any front skin. • Clarify the walkway locations. • Is there access to the sides of the vertical W6x20 I-beams? • Verify the roof overhang detail.