S.S. White Flex Shaft Design To Withstand High Stress
The “Flexcellent” technology combines dry film lubricants with traditional grease to improve performance at higher speeds and torque loads.

S.S. White Technologies has developed a new technology to improve performance and longevity of flexible shafts used in a range of aviation applications, such as thrust reverse actuation systems, flap and slat control systems, variable bleed valve systems, and cargo door application. The “Flexcellent” technology combines dry film lubricants with traditional grease to improve performance at higher speeds and torque loads.


Traditional flexible shafts, used in numerous applications involving high stress, can be vulnerable to internal wear and settlement over long period periods, S.S. White said. This occurs as the wires making up the flexible shaft rotate, moving across each other. “High loads and displacements due to torque transmission and bend radii mean the wear can become unacceptably high for long-endurance service life applications or where precise angular control is important,” the shaft specialist said. “The challenge is to sustain these characteristics over the product’s lifetime.”


This is particularly tricky since traditional solutions to improve wear resistance have limitations. Typical lubrication methods perform well at low speeds and torque load applications but are less effective at the higher speeds/torque loads. Alternating materials on the shaft layers can impair directional balance, the company added.


Dry film lubricants, however, have been successfully applied to shaft exteriors, but the challenge is to produce a shaft that can maintain the lubricant throughout the construction. This led to an investigation of a combination of the dry film lubricant with more traditional lubricants, the company said, adding that testing demonstrated that the use of a dry film lubricant combined with grease throughout the flexible shaft reduced the shaft’s temperature and wear rate, “enabling greater angular control over a longer lifetime than previously possible.”


The development of the new approach to lubrication has become even more important to meeting customer expectations, the company said, adding, “Over the years, customer service lifetime requirements have become ever more demanding, resulting in the expectation that end-of-service products should behave like new ones.”