Hapco is the industry-recognized pioneer on the research of wind induced vibration in aluminum poles. Our decades of research and testing has led to several patents in this category, giving Hapco Engineers the knowledge and background to assure our customers the safest, longest lasting pole designs.

We have learned from experience that poles supporting certain types of post-top mounted fixtures are more susceptible to first and second mode vibration. The rectangular or “shoebox” shaped luminaires, for example, seem to encourage second mode vibration, while more aerodynamic lightweight fixtures encourage first mode vibration. Any oscillation should be dealt with as soon as it becomes apparent to prevent damage to the pole or luminaire.

Hapco Damper Solutions

To minimize the effects of first or second mode vibration, Hapco has developed dampers which very effectively quell wind induced vibration of lighting poles.


Free Vibration Test Curves

Free Vibration of Test Pole with No Added Damping

Free Vibration of Test Pole with Impact Damper

First Mode Damper

Hapco’s patented First Mode Vibration Damper is field installed at the top of square poles. This damper very effectively reduces first mode vibration of square lighting poles. Due to potential vibration fatigue issues that can be associated with moderate wind conditions, First Mode Dampers are recommended for square poles with mounting heights greater than 25’ and for square poles with light loading fixtures less than 2.0 EPA. Fatigue related pole failures are not an indication of substandard material, workmanship or design of the pole and is not covered under Hapco’s standard warranty.

First Mode
U.S. Patent No. 7871186

Second Mode Damper

The Hapco Second Mode Damper was awarded the industry’s first patent in the vibration damping category in 1972. It is attached to the pole at approximately the midpoint of the pole, and can be factory bolted inside the pole or field mounted on the inside or outside of an existing pole.

Based on past experience, some Hapco poles include factory-installed Second Mode Vibration Dampers as a standard component. If the poles you intend to order are to be bridge mounted, used as camera poles, or may be subject to unusual site conditions, wide open terrain, steady or high energy prevailing winds, or other site conditions as mentioned, please make Hapco aware of these conditions. Or, if your installed poles are exhibiting oscillation, contact Hapco to pursue a damping solution that may include installing a Hapco Second Mode Damper on the poles.

Locations with high average wind speeds are more prone to pole vibration problems than locations with high maximum wind speeds. Areas of high average wind speeds can be identified on the U.S. Department of Energy Residential Scale 30 Meter Wind Map which can be accessed at the U.S. Department of Energy website.

Catalog No. 53185
Banded to Shaft
(Field Mounted)
Second Mode

Catalog No. 53373
Bolted Inside Shaft
(Factory Bolted)
Second Mode

Catalog No. 53884
Bolted Inside Shaft
(Field Mounted)
Second Mode