What is Free Flex Pivots?

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What is a Free-Flex® pivot bearing?

A Free-Flex® Pivot bearing is a completely packaged mechanism that utilizes crossed leaf spring flexures to provide rotational motion. Pivots are frictionless and stiction-free, and can have infinite lifetime. They are available in both cantilevered and double-ended configurations with 10 different diameters and 3 torsional spring rates for each diameter.

How do Free-Flex® Pivots move?

Free-Flex® Pivots derive their motion from an applied torque, which results in the crossed leaf springs deflecting and allowing the part to rotate. An external force such as an actuator or motor is required. Once moved, the pivot stores energy and springs back to its neutral position, allowing it to oscillate freely.

What makes a Free-Flex® Pivot bearing frictionless?

Free-Flex® Pivot bearings are frictionless because no parts come into contact with each other during movement, and no lubrication of any kind is required. This means no energy is lost to friction, resulting in extremely predictable motion when external forces are applied.

Are these the same Bendix, Lucas, TRW, or Goodrich pivot bearings?

Yes. Riverhawk acquired the Free-Flex® Pivots product line from Goodrich Corporation (formerly TRW, Lucas, Bendix) in 2004. We uphold the same quality standards as the original manufacturer.

What is the difference between a cantilever and a double-ended bearing?

The main difference is the way they are mounted, as well as having different load capacities and stiffnesses. Cantilever (single-ended) pivot bearings are generally easier to install, but double-ended pivot bearings offer higher load capacities and increased radial stiffness.

What is the difference between the -400, -600, and -800 denominations?

These denominations refer to spring thickness. The -400 series has a thicker spring with higher load rating and torsional stiffness but less rotational capability (±7.5°). The -800 series has the thinnest spring with lighter loads and lower spring rate but higher angular capability (±17.5°). The -600 series offers a middle ground between load, spring rate, and rotation (±12.5°).

What is the difference between a Vc load and a Vt load?

A Vc load places the springs into compression, while a Vt load puts the springs into tension. Load ratings differ between the two because springs in compression may experience buckling, whereas springs under tension do not.

What does torsional spring rate refer to?

Torsional spring rate is the level of torque required to rotate the pivot 1 degree. It remains constant as the pivot is rotated to higher angles, and is the same for equivalent classes of cantilever and double-ended parts. Manufactured parts typically fall within ±10% of the nominal listed spring rate.

Centershift is the radial movement of one segment of the pivot relative to the other when rotated. When one end is fixed and the other is rotated, the rotated axis moves radially while remaining parallel to the original axis. Centershift is predictable and depends only on pivot diameter and rotation angle — it is identical for both cantilever and double-ended pivots.

What cycle count is considered 'infinite life'?

A part is rated for infinite life when the stress induced in the flexures by applied radial loads and rotation falls below the fatigue limit of the material. For standard stainless steel parts, infinite life is defined at 60,000 psi.

Can Free-Flex® Pivot bearings be customized?

Yes, Riverhawk offers a wide variety of customization options including custom spring rates, additional lengths, increased diameters, and different mounting options. Special metals such as titanium, maraging steel, Inconel, and others have been used. Contact engineering to discuss your specific requirements.

What is the temperature range?

Standard pivots operate from -65°F to +250°F. With special materials and electron beam welded construction, extended temperature ranges are available. The pivots have been used in cryogenic (-400°F) space applications.

Can you test the mechanical properties listed in your catalog?

Yes, Riverhawk has the ability to measure most of the mechanical properties listed in publications. Test programs have been developed for various commercial and aerospace customers tailored to their specific needs.

FAQ | Free-Flex® Pivots

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Frequently Asked Questions

Find answers to common questions about Free-Flex® pivot bearings — from selection and configuration to loads, performance, and customization.

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