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Preliminary Detailed Design Review: P19129: Mechanical Heat Switch

This document provides an overview of the design, components, and plans for the mechanical heat switch project. It includes information on solenoid selection, support plate design, ratchet mechanism, bearings, fastening methods, thermal conduction path, thermal analysis, power board schematic, code functionality, proposed changes, bill of materials, and project plans.

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Preliminary Detailed Design Review: P19129: Mechanical Heat Switch

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  1. Preliminary Detailed Design Review: P19129: Mechanical Heat Switch Jake Watts-St. Germain, Eric Cooper, Megan McKendry, Paul Giovannetti, Anant Mehrotra, Roberto Rico Bernal November 15, 2018

  2. Agenda • Heat Switch Design • Individual Components • Mechanical • Electrical • Test Stand Design • Materials List & Cost • Areas of Concern • Next Phase Plans

  3. Heat Switch Design

  4. Solenoid Selection • Johnson Electric is original manufacturer • Allows custom ordering • Hole in shaft • Newark is our backup supplier • Cannot custom ordering • Would have to cut shaft

  5. Solenoid Housing • Dimension Problems (Width) • Fastening Methods • Will be manufactured in-house

  6. Support Plate • Connects Housing to arms • Has inner hole for ratcheting mechanism • Will be manufactured in-house

  7. Ratchet Mechanism • Uses one way rotating cylinders to reset ratchet • Work in progress • Last remaining mechanical component to be designed • Need to address assembly process concerns • Modify current design • Find spring

  8. Arms • Design Choices • Mount directly to support plate vs floating • Mounting holes for bearing, pivot and slot for spring • Overcoming friction from pivot • Opening angle (Roughly 3 degrees)

  9. Bearings • Ceramic bearings vs traditional metal bearings • Lubrication Differences • Material Differences • Can only use Silicon Nitride • Not Zirconia Oxide • Shoulder bolt (Connects bearing to supports) • Washer clamps to inner bearing ring • Allows outer ring to rotate

  10. Double Peanut Cam • Design Methodology • 45°vs 90° • Connected to Ratchet Mechanism

  11. Fastening Methods • Assembly uses #4-40, M2 and M3 fasteners • Use lock-washers for Housing and Support Plate • Loctite use • Could be used in areas to minimize thickness • Shoulder bolts for bearings

  12. Copper Set Screw Stanchion System • Main connection path between “salt pill” and cryostat • Adjustable system allows for adjustable end length + force • Screw will be manufactured in-house • Vendors don’t supply size we need

  13. Springs • Two total springs • One for back section behind arms • One for ratchet assembly (not yet complete)

  14. Thermal Conduction Path • From copper set screws to arms • Arms transfer heat directly to support plate • Support plate transfers heat directly to housing • Housing transfers heat to cryostat plate

  15. Thermal Analysis - Heat Flux • Model Simplification • Boundary Conditions • Heat Flow Source • Cryoplate

  16. Thermal Analysis - Temperature

  17. Power Board Schematic • This board will power the motor at 38V output with a 24V-28V input

  18. Power Board Manufacturing Cost Options • Basic Board Cost = $79 Plus parts ($18.75) • For an additional $34 we can upgrade to include solder mask and a silkscreen • More professional look + easier references for troubleshooting design • Thisoption limits us to an area of 3.8 x 2.5 inches • Boards will be manufactured but assembled by us in the CEMA lab • No assembly charge

  19. Code Functionality • The code will be implemented as three main functions: • Heat Switch Actuation • Cycle Testing • Standard Operation • Heat Switch Actuation: Basic open and close based on user input: • Initial use to make sure electronics are behaving as expected • Further to make sure all connections are in place for cycle testing or standard operation • Cycle Testing: Automated open/close test for user input amount of cycles • Main use for reliability testing • Standard Operation: Simulate heat switch actuation in rocket • Code that moving forward will be implemented in full rocket

  20. Code Flow Chart Initial User Input (Program Select) Heat Switch Actuation Standard Operation Cycle Testing User On/Off Number of Cycles Data Out / Real Time Plot

  21. Proposed Changes / Concerns • More allowable width • 3.5 cm puts bearings directly at solenoid axle. No room for cam. • 3.5 cm creates zero-thickness at sides of housing • More area heat conduction • Copper foil soldered to arms and base (like Grant Wilson design) • Salt Pill contact during vibration

  22. Bill of Materials • Does not include • Shipping costs • Educational discounts from vendors

  23. Project Plan

  24. Project Plan • Mechanical • Complete Final Design (11/15 - 11/29) • Final Ratchet Design (11/15 – 11/27) • Resistor Housing + Stand (11/17 - 11/20) • Structural Analysis for critical parts (11/15 – 12/4) • Improve Thermal Model (11/27 – 12/4) • Vibration Testing Rig (11/27 – 12/4) • Completed Test Plans (11/29 – 12/6) • Manufacturing Plans (11/17 – 12/6) • Assembly Plans (11/15 – 12/4) • Electrical • Completed Code (11/15 - 11/29) • Demo Board Schematic (11/15 - 12/6)

  25. Project Plan • Materials • Cost Estimates (11/15 – 11/29) • Final Part Selection + Finalize BOM (11/17 – 11/31) • Determine critical lead times (11/15 – 11/29) • Post – MSD I plans • Winter break plans (11/27 – 12/6) • MSD II plans (11/27 – 12/6)

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