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Similar to Laminated Rubber Bearings, Heavy Duty Composites for Aerospace and Undersea
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Laminated Rubber Bearings, Heavy Duty Composites for Aerospace and Undersea
- 1. Laminated Rubber Bearings Heavy Duty Composites for Aerospace and Undersea
- 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
- 5. (Seen from above, moving up on picture)
- 6. 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
- 7. (Seen from above, moving up on picture)
- 8. Laminated Rubber / Elastomeric Bearings •Easily handle tons of CF •Oscillate at high frequency •No lubrication •NR for high resilience Used on most helicopters now
- 9. Enstrom – First with Elastomeric Bearings
- 10. Enstrom Bearing Design • 2-1/4" in diameter • More than100 rubber & brass layers each • All layers 0.002” thick • 18,000 lbs. CF
- 11. Small Wind Turbines • Blade pitch angle variable with wind • Increase efficiency
- 12. 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
- 13. One-inch Square Laminate Pads • 40 layers .002’ brass • 39 layers .002” NR • Bendable • RIGID
- 16. • RRC specializes in laminates with very thin layers • Small helicopters • Chemical bond of NR to hi-tensile brass • Lack of adhesive reduces thickness • Larger helicopters use thicker, fewer layers
- 18. Planar & Chevron • Planar - angular oscillation & lateral movement - easier to make – no metal forming • Chevron - precludes lateral shifting - permits taller bearing for given load
- 19. Conical • Combined radial & thrust loads • Angular motion about axis
- 20. Cylindrical (Radial) Bearing • Circular & axial motion • Wrapped around shaft • Axial thermal expansion of shaft • Silicone rubber for heat
- 21. Spherical Bearings • 3D angular motion about center - rotation about longitudinal axis - tilting L/R and in/out of screen
- 22. Helicopter Spherical Bearing • Many large helicopters • Ordinary pitch oscillation • Also lead-lag & flapping
- 23. Design Factors • Diametral dimensions • Height • Load forces • Torsional stiffness • Oscillatory torsional shear strain • Fatigue life • Angular range.
- 24. 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
- 25. Bearing-Seals • A more recent development by RRC • New design opportunities for undersea craft
- 26. 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 can't penetrate - Solid barrier around central hole
- 27. 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
- 28. 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.
- 29. 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.
- 31. 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
- 33. 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
- 34. 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
- 35. Laminated Rubber Bearing Technology • Simplicity • Low cost • No lubrication • Reliability • Long life For vehicles that Probe the sky and depths of the sea