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123:. Stockbridge obtained US patent 1675391 on 3 July 1928 for a "vibration damper". His patent described three means of damping vibrations on lines: a sack of metal punchings tied to the line; a short length of cable clamped parallel to the main cable; and a short (30 in, 75 cm) cable with a concrete mass fixed at each end. This last device developed into the widely used Stockbridge damper.
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Vibrations in the main cable were passed down through the clamp and into the shorter damper, or "messenger", cable. This would flex and cause the symmetrically-placed concrete blocks at its ends to oscillate. Careful choice of the mass of the blocks, and the stiffness and length of the damper cable
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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
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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
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for which vibration is predominantly 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
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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.
39:-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.
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The
Stockbridge damper targets oscillations due to aeolian vibration; it is less effective outside this amplitude and frequency range. Aeolian vibration occurs in the vertical plane and is caused by alternating
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of the damper to that of the line, and greatly attenuate oscillation of the main cable. Since
Stockbridge dampers were economical, effective and easy to install, they became used routinely on overhead lines.
191:(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.
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addition to bending it up and down. Additional intra-strand friction was created in the damper cable, dissipating significantly more energy.
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Guidelines for the
Installation, Inspection, Maintenance and Repair of Structural Supports for Highway Signs, Luminaries, and Traffic Signals
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to the cable and represents the principal cause of failure of conductor strands. The ends of a power line span, where it is clamped to the
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Markiewicz, M. (29 November 1995), "Optimum dynamic characteristics of
Stockbridge dampers for dead-end spans",
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The
Stockbridge damper was invented in the 1920s by George H. Stockbridge, who was an engineer for
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pattern on the line consisting of several wavelengths per span. Aeolian vibration causes damaging
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The most vulnerable section of the cable is where it is clamped to the end of an
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Kiessling, Friedrich; Nefzger, Peter; Nolasco, Joao F.; Kaintzyk, Ulf (2003),
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has an amplitude measured in metres and a frequency range of 0.08 to 3 Hz
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tools meant it was possible to retrofit dampers to lines while energised.
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on the leeward side of the cable. A steady but moderate wind can induce a
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Wind can generate three major modes of oscillation in suspended cables:
283:, vol. FHWA NHI 05-36, US Department of Transportation, March 2005
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used to suppress wind-induced vibrations on slender structures such as
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EPRI Transmission Line
Reference Book: Wind-Induced Conductor Motion
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Tuned mass damper used to suppress wind-induced vibrations
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Stockbridge dampers installed on high voltage power lines
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164:Dogbone dampers on the road-support cables of the
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115:Stockbridge's original concrete block design
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357:(3rd ed.), Macdonald, pp. 216–219
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470:. Philip Dulhunty. pp. 280–282.
420:High Voltage Engineering and Testing
353:McCombe, John; Haigh, F.R. (1966),
194:Overhead transmission lines form a
152:A modern design with metal weights
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513:Electric power systems components
305:, Springer, pp. 311–312,
243:Journal of Sound and Vibration
31:, long cantilevered signs and
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418:Kiessling, Friedrich (2001),
171:Another modern design is the
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121:Southern California Edison
466:Dunhunty, Philip (2009).
422:, IET, pp. 190–191,
392:Electrical Power Systems
51:Wind-induced oscillation
355:Overhead Line Practice
263:10.1006/jsvi.1995.0589
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484:Vibrationdata article
444:Building aerodynamics
389:Wadhwa, C.L. (2006),
372:U.S. patent 1,675,391
222:Tacoma Narrows Bridge
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442:Lawson, Tom (2001),
333:, EPRI 1012317, 2008
303:Overhead Power Lines
201:cable-stayed bridges
129:mechanical impedance
85:shedding of vortices
33:cable-stayed bridges
29:overhead power lines
468:Never a Dull Moment
255:1995JSV...188..243M
97:transmission towers
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68:(sometimes termed
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21:Stockbridge damper
402:978-81-224-1773-9
134:Live-line working
66:Aeolian vibration
25:tuned mass damper
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489:"Cable clingers"
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101:self-damping
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107:Description
502:Categories
287:12 October
229:References
189:anti-nodes
205:guy-wires
138:hot stick
211:See also
196:catenary
37:dumbbell
518:Weights
494:Q&A
251:Bibcode
173:Dogbone
70:flutter
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136:using
60:Gallop
35:. The
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448:ISBN
424:ISBN
397:ISBN
307:ISBN
289:2008
76:Wake
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19:A
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