Defence When it Matters, the Spring Counts

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Defence manufacturers rely on wave springs from the AFC portfolio.

The flat wire wave springs from Smalley are a proven problem solver in the realisation of kinematic assemblies. They are among the core products in the portfolio of AFC Europe (formerly TFC) and are currently being increasingly used by manufacturers of defence and security systems. Specific applications include absorbing defined loads, setting preloads and compensating axial tolerances.

Whether it is helicopter winches, mobile targeting devices or the gear systems of special vehicles: the realisation of kinematic assemblies that must operate reliably and precisely under extreme loads is undoubtedly one of the central tasks of designers of defence and security systems. For engineers, procurement specialists and buyers in the industry, this means that when selecting all relevant machine elements, their focus must be on components that meet particularly high quality requirements. Under these demanding conditions, Smalley wave springs (supplied by AFC Europe) have gained considerable importance. Time and again, these elements made from rolled and coiled flat wire prove to be a welcome solution for typical challenges arising in the design of kinematic precision assemblies. Whether it is the absorption of specific loads, the targeted setting of preloads, the reliable compensation of bearing clearances or the compensation of operational tolerances, Smalley wave springs often demonstrate clear advantages over conventional round wire springs or stamped sheet metal components. Regardless of their dimensions, they can be specified very precisely in terms of load capacity, tolerance, material and spring rate. And when, in addition to solving the kinematic problem, reducing installation space and miniaturising the assembly are required, the wave spring proves to be almost unbeatable.

The load determines the layers

As an exclusive partner of Smalley, AFC Europe offers a wide range of single-layer and multi-layer wave springs in many sizes as well as metric and imperial dimensions. The single-layer variants are primarily suitable for designs with short spring travel, where low to medium loads need to be handled. They are available with open gaps or overlapping ends and are installed with an interference fit, allowing free and unrestricted spring operation.

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The multi-layer wave springs in the AFC portfolio, on the other hand, feature continuously and uninterruptedly coiled turns. They carry the product designation Crest-to-Crest®, indicating that all peaks (maxima) of the flat wire touch each other. They are supplied in imperial and metric series and in many sizes with up to 15 turns. In addition, depending on the installation scenario, the designer can choose between two end types: parallel ends, which form circumferentially closed contact surfaces, or waved ends that rest on the peaks of the flat wire waves.

In a multi-layer wave spring, the spring rate decreases proportionally with the number of turns. This means it is an ideal solution for applications with long spring travel where uniform and linear force development is required. Neither alignment of the turns nor the use of shims nor fixation by welding points is necessary. This simplifies the design and minimises both assembly effort and the number of components. Not to be overlooked: Crest-to-Crest® wave springs enable the greatest reductions in installation space. With the same spring travel and load capacity, they require up to 50 percent less axial installation space than a round wire or coil spring. This prevents design collisions and enables significant space optimisation.

Wide range of applications

In addition to the examples mentioned at the beginning, Smalley wave springs are also used in defence and security technology in recoil systems of launch systems, in control units of missiles, in stabilisation axes of gyroscopes, in optics of navigation systems as well as in satellite housings and servo drives. In some cases, the focus is on motion guidance or energy absorption, in others on providing preload, damping vibration or controlling axial loads.

As a specialised solution for preloading bearing bushings of hydraulic telescopic tubes and for applications with limited radial installation space, the narrow-section wave springs of the YSSR-N type have proven effective. For assemblies where large forces are at work and long spring travel is required, AFC’s consultants recommend the Interlaced wave spring type. It is a combination of up to three integrated Crest-to-Crest® springs and can substitute stacked disc springs or nested coil springs. This reduces assembly effort and, because neither stacking nor alignment is required, the design of housings and supports can be eliminated entirely. Also of interest for defence applications is the Nested Spirawave® wave spring, designed for high-load use. Its flat wire turns run parallel and lie flush and fully in contact. In addition, Smalley guarantees that it is consistently manufactured from a single piece of flat wire. A Nested Spirawave® can deliver up to three times the spring force of a single-layer wave spring. This eliminates the need to stack or nest multiple single-layer wave springs, and misalignment or uneven loading does not occur.