09-08-2020
Are you a long-time reader of our blog posts? Then you’ve seen us share insight about the effects of first and second-mode vibrations. (Missed it? Read all about it here.)
You may be tempted to resort to radical measures in order to protect your new gorgeous light poles, but the local mayor or end customer likely won’t approve of building-thick brick walls around each pole. Another effective option: vibration dampeners.
A vibration dampener is a device that attaches to the light pole that absorbs energy from the wind, disrupting the resonance of the pole. After enough collisions, your pole is considered “effectively dampened,” which means that the dampener is successfully minimizing the intensity of each vibration.
Types of Vibration Dampeners
First-mode vibrations are caused by sudden, high-velocity gusts of wind. They cause poles to sway. Most poles are designed and built to handle such movement, but it can be alarming to see out in the field. A vibration dampener may be used to mitigate swaying. Second-mode (a.k.a. Aeolian) vibrations are caused by steady, low-velocity, high-frequency winds. These vibrations can be extremely damaging to a structure by leading to stress fractures, cracked lamps, and corrosion. They can even knock down a light pole. Vibration dampeners can also mitigate the destructive impacts of these types of movement.
Ball in a Box
A lead ball is epoxy-coated and placed inside a box attached at the top of the pole. Lead helps absorb some of the resonant energy from the wind through local deformations. Those deformations are small and believed to not significantly degrade the performance of a dampener over time. The more balls you place in the box, the better they absorb energy. This dampener is typically used to mitigate first-mode vibration and can be installed in the field.
Rod in a Canister
A rod in a canister is placed inside the light pole and can typically be recognized by two bolts protruding on the outside of the pole. This dampener counteracts the low amplitudes and higher frequencies associated with second-mode vibrations. These dampeners are usually factory installed.
Chain and Tube
A chain encased in a plastic tube is run two-thirds the length of the pole and disturbs the harmonic cycling of the shaft by randomly touching the inside surface of the pole. Any agitation caused by the wind transfers to the tube and chain. This style of dampener can be either factory or field installed. Learn more here.
Before installation, bring an electrician on-site to inspect your pole and ensure the chain will not interfere with any electrical components. Some items, like terminal blocks, may need to be temporarily removed for proper installation. See full installation instructions.
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