General Overview FAQs
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. Free-Flex® Pivots are available in both cantilevered and double ended configurations with 10 different diameters and 3 torsional spring rates for each diameter.
The main difference between our two product types is the way they are mounted, as well as having different load capacities and stiffnesses. Cantilever pivot bearings are generally easier to install, but double ended pivot bearings offer different advantages, such as higher load capacities and increased radial stiffness.
Free-Flex® Pivots derive their motion from an applied torque, which results in the crossed leaf springs deflecting allowing the part to rotate. Because of this, the pivot requires an external force, such as an actuator or motor, to make it move. However, due to the design of the part once moved the pivot will be able to store the energy and spring back into place after its initial rotation. This stored energy allows the pivot to oscillate freely about its neutral position.
Free-Flex® Pivot bearings are frictionless due to their design. Since the pivot has no parts that come in contact with each other during their movement, and since there is no lubrication of any sort required, there is no energy lost as a result of any friction. This allows for the Free-Flex® Pivot to have extremely predictable motion when external forces are applied.
Riverhawk has the capacity to create custom Free-Flex® Pivot bearings that can achieve higher maximum angular displacements. Contact our engineering team to discuss your application and see what solutions we have.
The different denominations of pivot are the thickness of the pivot bearings spring. A -400 series pivot will have a thicker spring, which means more load rating and higher torsional stiffness, but less capability when it comes to rotation. On the other end of the spectrum the -800 series pivot has our thinnest spring, which means light loads and low spring rate, but higher angular capability. The -600 series springs offer a solid middle ground between load, spring rate, and rotation.
Yes, Riverhawk can offer a wide variety of different customization options for our Free-Flex® Pivot bearings. We have the capability to provide pivots with custom spring rates, additional lengths, or increased diameters. We can also add different mounting options to parts. In some cases special metals have been used, such as titanium, maraging steel, custom stainless, Inconel, and others. We can design to fit almost any need. Contact engineering to learn more about all the potential customization options.
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 past. We are the original.
Yes, we have the ability to measure most of the mechanical properties we list in our publications. Over the years we have developed many test programs for various commercial and aerospace customers that were tailored to their needs.
Linear Flexure FAQs
A traditional Free-Flex® Pivot bearing provides the user with rotational motion. A linear flexure, on the other hand, provides a translational motion. The top and the bottom of the linear flexure remain parallel throughout its range of motion, and the flexure loses some height as it travels as well.
No, there is not currently a standard set of part numbers for linear flexures. If you are interested in using a linear flexure in your design please contact us so we can work with you to decide what size flexure may be needed for your application.
Sustainability FAQs
Free-Flex® Pivots at Riverhawk Company takes sustainability seriously. As a company, we’ve taken a number of steps to reduce our carbon footprint. This includes transitioning our entire facility to LED lighting which reduces energy consumption significantly. Our water dispensers throughout the facility save over 23,000 plastic bottles per year, which is the equivalent of 4,500 miles of CO2 emissions from an average passenger vehicle. We devotedly recycle machining waste, plastics, and cardboard. These efforts matched with the infinite life of our Free-Flex® Pivots contribute to our circular economy.
Free-Flex® Pivots at Riverhawk Company fully complies with all applicable New York State, DEC, EPA, and OSHA regulations, as well as international and domestic standards including REACH, RoHS, PFAS, TSCA, CMRT, Prop 65, and POPs. Our facility operates as a low-quantity hazardous waste generator and takes great care to handle and dispose of materials
Absolutely! We’re happy to provide supplier declarations and other supporting documents upon request.
Loading FAQs
The difference in these two loads has to do with both how the load is being applied to the outside diameter of the part, and how the load effects the springs. A load in the Vc direction will place the springs into compression, while a Vt load will put the springs into tension.
Load ratings for our parts are different for Vc and Vt loads due to the fact that when springs are placed in compression they may experience buckling. Springs that are under tension do not experience this problem.
No, cantilever and double ended pivots do not share the same load ratings. Cantilever bearings support loading from only one end, which results in more internal stress in the springs. Double ended parts support the load more evenly.
Torsional Spring FAQs
Torsional spring rate refers to the level of torque required to be applied to one of our pivots in order to rotate the part 1-degree.
Yes, torsional spring rate is the same for the equivalent classes of cantilever and double ended parts.
Torsional spring rates of parts typically fall within +/- 10% of the nominal listed spring rate. In situations where an exact spring rate is required, additional testing can be carried out in our facility.
Yes, the torsional spring rate will remain constant as the pivot is rotated to higher angles.
Radial loads can have a different effect on torsional spring rate depending on the direction the load is applied. Loads applied to the pivot that place the flexures in compression typically increase the torsional spring rate, while loads applied in tension typically decrease the torsional spring rate. A chart with relevant information on how torsional spring rate can vary with applied radial loading can be found in our Engineering Data.
Yes, a custom pivot can be designed and made to better match any custom spring rate that may be needed for any projects.
Centershift FAQs
Centershift refers to the phenomenon that pivots undergo when they are rotated. When rotated, the different segments of the pivot can move radially relative to one another. When one end of a part is fixed and the other is rotated, the axis of the rotated segment moves radially but remains parallel to the original axis. Centershift is a predictable phenomenon, and is dependent upon pivot diameter and the angle the part is rotated to.
Yes, centershift is identical between cantilever and double ended pivots.
No, spring thickness does not play a part in centershift. Centershift is only effected by part diameter and the amount of rotation.
Centershift can be calculated using the guide provided in our Engineering Data.
Life Expectancy FAQs
We consider a part rated for infinite life at the point where the stress induced in the flexures of the part by the applied radial loads and stresses induced by the rotation of the part is below the fatigue limit of our material. Standard parts are made with stainless steel, so the fatigue limit has been set for infinite life at a value of 60,000 psi. Parts in applications that exhibit stress levels lower than this value can be considered as having infinite life.
No, cantilever and double ended parts do not have different life expectancy.
Mounting FAQs
There is no one way to mount a Free-Flex® Pivot. That being said, there are typically a few ways we recommend. Our Flexural Pivot Suggested Mounting Methods details many of the best ways to mount our pivots.
Yes, there are a number of options when it comes to customization for different methods of mounting. We have the capability to add in flats on the outer diameter of parts for set screws. We can also add in keyways, grooves, and tap holes for screws within the outer diameter of the part. Additionally, we have added flanges and other similar structures to the outside of the part.
Yes, pivots can be mounted using adhesives or epoxies. When mounting this way be sure to avoid getting any adhesive or epoxy within the pivot itself. Adhesives inside the pivot or that block any of the parts movement will have an adverse effect on part performance.
Yes, we have tools in order to help when trying to press fit install our parts. Contact us to get more information on these items.
Operating Environment FAQs
We typically recommend a maximum operational environmental temperature of around 375 degrees Fahrenheit (~ 190 degrees Celsius). Pivots can operate in higher temperature ranges, but doing so may cause damage to the pivot bearing.
Standard Free-Flex® Pivot bearings have successfully been used in cryogenic operating conditions in the past. There are some additional considerations to make when using a pivot bearing in cryogenic conditions. These considerations have to do with the pivots’ weakness to impacts at low temperatures, and also with the thermal expansion of both the part and whatever housing is used to clamp the part. If you have concerns about how a pivot may act in your specific condition, please reach out to our engineering team.
Our Free-Flex® Pivot bearings are manufactured using 400 series stainless steel. Due to the makeup of our parts, corrosion is possible, and it is important to make sure pivots are kept clean and in an environment where such corrosion cannot take place.
Yes, Free-Flex® Pivot bearings are ideal for use in a vacuum. Our parts exhibit no outgassing of any sort, and are perfect for use in vacuum or clean room environments.
Resources
contact us
Got a technical question or a project in mind? Our engineers are ready to help.
