Doublerods

Doublerods are a term used in mechanical engineering and related fields to describe a pair of slender rods designed to work in tandem to increase stiffness, share load, or transfer motion in a mechanism. The concept is not standardized, and the exact geometry varies by application, but common implementations feature two parallel members connected by a yoke, clamp, or cross-link at one or both ends, ensuring near-equal length and synchronized movement.

Materials are typically steel, aluminum, or carbon fiber composites, chosen for strength-to-weight ratio and corrosion resistance. Ends may be threaded, bolted, or welded to hubs, with bushings or bearings to allow rotation or sliding. In some configurations, the rods are joined along their length by a narrow cross-member or by a belt or gear system to enforce parallel motion.

In robotics, doublerods are used in parallel-link actuators and linear guides to double stiffness without a large increase in footprint. In structural assemblies, they may act as reinforcing members in frames, distributing axial loads between adjacent members to reduce local bending. In automotive chassis bracing, pairs of tie rods arranged as doublerods can improve torsional stiffness.

Design considerations include axial load capacity, buckling risk for long slender rods, alignment tolerances, and weight. The benefit is balanced load sharing; the drawback can be added complexity and maintenance of joints. Terminology and usage vary; some designers simply call them two tied rods or parallel rods. As a result, the label "doublerod" may refer to slightly different configurations depending on the industry.