Flex Pivot Helicopter Application

1
Flex Pivot Helicopter Application

• Goodrich Corporation
• Team Members
• Matt Chverchko
• Danielle Lesser
• Andy Styer
• Josh Tinelli

2
Objectives

• Problem Statement Determine possible helicopter
  applications for the Goodrich Free-Flex Pivot
• Develop basic understanding of how Flex Pivot
  works
• Brainstorm and propose concepts to Goodrich
• Proceed to design and development of selected
  ideas

3
The Free-Flex Pivot

• A unique bearing concept for applications with
  limited angular travel.

The Free-Flex Pivot consists of perpendicular
flat springs supporting cylindrical
counter-rotating sleeves.
4
Flex Pivot Characteristics

• High radial stiffness
• High axial stiffness
• Frictionless
• Stiction-Free
• Infinite Cycle Life

• Exceptional Repeatability
• Predictable Performance
• Lubrication Free
• Maintenance Free
• Electrical Continuity

• Wide Temperature Operating Range -400F to
  1200F

5
Flap, Lag, and Feathering
There are three potential applications for the
Flex Pivot in an articulated rotor. Currently,
bearings are being utilized in the following
locations, as denoted by the circles in Figure 1.
Flapping (Side View) Lagging (Top
View) Feathering (Side View)
6
Articulated Rotor Hub
An articulated rotor facilitates vertical,
horizontal, and torsional blade motion at three
specific hinge positions

• Pitch Hinge
• Drag Hinge
• Flapping Hinge

7
Blade Free Body Diagram
z
AF
Omega
CF
K
IF
Beta
n, y
e
8
Force Equation

• The forces acting on the blades of a fully
  articulated hub include
• Inertia Force, IF
• Centrifugal Force, CF
• Aerodynamic Force, AF
• Spring Moment, SF
• After analyzing these various forces, it was
  determined that the bulk of the forces on the
  blade comes from the centrifugal force, expressed
  by the following force equation
• Fma, where aR?2

9
Implementation

• The project will replace the conventional
  bearings of the Pitch Hinge of a RC helicopter
  hub with the Flex Pivot bearings.

10
Final Design

• Completed design was assembled without incident
  using ½ cantilevered series 800 Flex Pivots.
• Additional modifications for proper testing would
  be

• Damping mechanism to replace rubber boots
• More secure mounting method
• Initial blade positioning may be modified for
  proper flight operation

11
Project Continuation

• Better hub design could incorporate Flex Pivots
  in the lead-lag and flapping positions
• Extensive testing on more durable hub
  modifications to further prove the Flex Pivot
  design concept
• For full-speed testing, Rotorcraft Center test
  stand would require modifications to ensure
  sufficient operator protection

12
Questions?