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Laminated Rubber Bearings, Heavy Duty Composites for Aerospace and Undersea

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Developed the concept of high-load rubber laminate bearings and the first application for helicopter blade retention in place of ball or roller bearings. LAMIFLEX Bearing-Seals for underwater hermetic shaft seals are a more recent innovation.

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Laminated Rubber Bearings, Heavy Duty Composites for Aerospace and Undersea

  1. 1. Laminated Rubber BearingsHeavy Duty Composites for Aerospace andUndersea
  2. 2. Laminated Rubber Bearings (Elastomeric Bearings)• Composite of elastomer and metal layers• Support massive structures -Permit thermal expansion -Isolate bulidings from earthquakes -Big, maybe 1/2 inch thin• Small & dynamic -Helicopters -Undersea
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  4. 4. Heavy Duty for a Thrust Bearing • Tons of CF while oscillating +/- a few degrees • Early failure of ball / roller bearings -spalling, fretting corrosion A New Idea was needed --- Laminated Rubber Bearings
  5. 5. (Seen from above,moving up on picture)
  6. 6. Laminated Rubber / Elastomeric Bearings•Easily handle tons of CF•Oscillate at high frequency•No lubrication•NR for high resilienceUsed on most helicopters now
  7. 7. Enstrom – First with Elastomeric Bearings
  8. 8. Enstrom Bearing Design • 2-1/4" in diameter • More than100 rubber & brass layers each • All layers 0.002” thick • 18,000 lbs. CF
  9. 9. Small Wind Turbines • Blade pitch angle variable with wind • Increase efficiency
  10. 10. Compression Very Slight• At 10,000 psi pressure on bearing - thinner by a few sheets of paper - about .010 of an inch• Rubber layers can’t squeeze out - because rubber layers are very thin -only .002 of an inch thick• Compression due to volume decrease
  11. 11. One-inch Square Laminate Pads • 40 layers .002’ brass • 39 layers .002” NR • Bendable • RIGID
  12. 12. • RRC specializes in laminates with very thin layers• Small helicopters• Chemical bond of NR to hi-tensilebrass• Lack of adhesive reduces thickness• Larger helicopters use thicker, fewer layers
  13. 13. Planar & Chevron• Planar - angular oscillation & lateral movement - easier to make – no metal forming• Chevron - precludes lateral shifting - permits taller bearing for given load
  14. 14. Conical• Combined radial & thrust loads• Angular motion about axis
  15. 15. Cylindrical (Radial) Bearing • Circular & axial motion • Wrapped around shaft • Axial thermal expansion of shaft • Silicone rubber for heat
  16. 16. Spherical Bearings• 3D angular motion about center - rotation about longitudinal axis - tilting L/R and in/out of screen
  17. 17. Helicopter Spherical Bearing • Many large helicopters • Ordinary pitch oscillation • Also lead-lag & flapping
  18. 18. Design Factors• Diametral dimensions• Height• Load forces• Torsional stiffness• Oscillatory torsional shear strain• Fatigue life• Angular range.
  19. 19. Some Relationships• Torsional Stiffness - prop. to 4th power of diameter - inverse with height• Torsional Shear Strain for given angle - prop. to diameter - inverse with height• Fatigue Life - Max oscillatory torsional shear strain - internal pressure - other factors
  20. 20. Bearing-Seals• A more recent development by RRC• New design opportunities for undersea craft
  21. 21. Undersea Bearing-Seal It’s the same thing!-An ordinary laminated rubber bearing - Top and bottom enclosed•Circular body makes a hermetic seal - Seawater outside cant penetrate - Solid barrier around central hole
  22. 22. Undersea Bearing-Seal It’s the same thing!• Seals against immense pressure -tested to 17,000 psi• No flimsy sliding surfaces like lip or face• Immune to sand and grit• Torque remains constant with depth
  23. 23. What can we do with a bearing-seal?• Suppose we have a pressure vessel - like a submarine• And suppose we want to have a sealed shaft that extends from the inside of it to the outside - like a diving plane shaft• We can do that with a bearing-seal.
  24. 24. AUV• Small autonomous robotic submarine• Looks like a torpedo, but leisurely• Loaded with sensors - pressure, temps, sonar, guidance• Pre-programmed for a mission over area• Military, Scientific, Offshore Oil & Gas - mine-hunting for the Navy - sensing ocean variables - inspect underwater oil & gas pipelines.
  25. 25. Application of Bearing-Seals• Mount & seal external hydrofoils that can control AUV: - direction by rudder - climb/descent by diving planes• Even “fishtail” propulsion - swivelling tail fin back & forth• Advantage of actuation in air environment - low cost, off shelf actuators - no worries about seawater corrosion
  26. 26. Typical Bearing-Seal • OD = 2.06", ID = 1", ht. = 1/2“ • 80 hi-tensile brass + 78 natural rubber layers, both .002" thick • 10,000 psi water pressure outside • +/- 15 degrees for 1,000,000 cycles • Also cycled at max sea depth, 17,000 psi
  27. 27. Bearing-Seal application similar to helicopter use• Bearing - as well as hermetic seal• Angular movement/oscillation +/-15 degrees• High force -intense hydrostatic pressure instead of centrifugal force• Millions of cycles
  28. 28. Laminated Rubber Bearing Technology• Simplicity• Low cost• No lubrication• Reliability• Long life For vehicles thatProbe the sky and depths of the sea

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