page_title: Stockbridge damper
section_title: Modern designs
hierarchical_section_title: Stockbridge damper / Modern designs
caption_attribution_description: English: A Stockbridge damper clamped to an overhead line
context_page_description: A Stockbridge damper is a tuned mass damper used to suppress wind-induced vibrations on slender structures such as overhead power lines and long cantilevered signs. The dumbbell-shaped device consists of two masses at the ends of a short length of cable or flexible rod, which is clamped at its middle to the main cable. The damper is designed to dissipate the energy of oscillations in the main cable to an acceptable level.
context_section_description: Modern designs use metal bell-shaped weights rather than Stockbridge's concrete blocks. The bell is hollow and the damper cable is fixed internally to the distal end, which permits relative motion between the cable and damping weights. To provide for greater freedom of motion, the weights may be partially slotted in the vertical plane, allowing the cable to travel outside the confines of the bell. Some more complex designs use weights with asymmetric mass distribution, which enables the damper to oscillate in several different frequency modes and ranges.
  Another modern design is the Dogbone invented by Philip Dulhunty in 1976 is so called due to its configuration, a larger metal sphere attached to the end of the damper, with a smaller sphere projecting sideways from it, resembling a dog's bone. The damper offsets the weights sideways in order to introduce a third degree of freedom, twisting the damper cable in addition to bending it up and down.  Additional intra-strand friction was created in the damper cable, dissipating significantly more energy.
  The most vulnerable section of the cable is where it is clamped to the end of an insulator string, so dampers are typically installed at the nearest anti-nodes (points of maximum displacement) either side of the clamp. There are thus normally two dampers per span, though more can be installed if necessary on longer spans.
  Overhead transmission lines form a catenary for which vibration is predominately in the vertical plane. When more than one plane of vibration is anticipated, Stockbridge dampers may be mounted at right angles to each other. This is common when the cable runs in a vertical or off-horizontal plane, for example in cable-stayed bridges or radio mast guy-wires.
caption: A modern design with metal weights
exif: {}