BannerSaver Wind Tunnel Test Video
BannerSaver™ is a patented light pole bracket which utilizes a spring tension system to keep banners in place during normal conditions and allows them to rotate as wind speed increases to reduce wind-load forces and light pole liabilities.
Independent tests, developed by TranTek Drive Systems were conducted to determine how much wind-load is transferred to a light pole using a variety of banner mounting devices including 1. BannerSaver™, 2. a flexible bracket and 3. a fixed bracket.
The banner in wind test apparatus simulated a light pole and was equipped with sensors to detect banner deflection and pole forces. Known wind speeds were provided by Behr America, a subsidiary of Behr GmbH and Co. KG, in a calibrated wind tunnel. The nozzle was set at a midpoint condition and banners were positioned 3.7 metres away. These conditions assured consistent air distribution to the entire profile and allowed wind speeds up to 160 kmph.
Forces were measured by a very precise load cell with a normal range of 0 to 227 kgs and a linearity specification of ± .0025% of full scale. Post-test wind speeds above 16 kmph were certified by Behr as accurate to within 1%.
Wind tunnel tests performed using BannerSaver™ and two 760mm x 2030mm light pole banners showed that the wind-load never exceeded 200 lbs (91 kgs) at wind speeds in excess of 145 kmh, while the other bracket systems tested yielded loads in excess of 227 kgs under the same conditions. (Click on the images below for larger versions).
- Record Static Conditions - Diagram A.
- Start wind tunnel and record base wind speed, force on banner pole, and deflection. Wind speeds were held for two minutes while increasing wind speed at 16 kmph increments.
- Repeat procedure on comparative brackets.
The test results clearly illustrate the advantages of BannerSaver’s patented wind deflection technology.
The most obvious and unique characteristic of the device is its ability to limit the forces to the pole by “spilling” the wind away.
In the test (see Diagram B) this spilling occurred between 42 and 52 mph (67 and 83 kmph). As the wind force overcame the BannerSaver™ spring force, the banners changed direction.
They started out perpendicular to the wind, then billowed and turned such that at over 112 kmph the middle of each banner became partially hidden behind the pole.
Calculated Area of Reduction
Using the drag equation for air, derived from Bernoulli’s equation, the theoretical force at a given wind velocity can be calculated and directly compared to the measured force. From that comparison the reduction of banner area can be derived for each bracket.
Example: At 90 mph (145 kmph), the theoretical force on two 30” X 80” (760mm x 2030mm) banners is: F = (90)2 * 33.3*.00256 = 690 lbs (313 kgs)
The following table shows the effective force & reduction of banner area for the three banner types tested:
|Force||247 kgs. (Avg.)||240 kgs. (Avg.)||41 kgs. (Avg.)|