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2 years ago in Environmental Economics By Pavitra

What engineering standards specify the procedures and coefficients for calculating wind load torque on a rotating parabolic antenna for motor sizing?

I'm specifying the drive motors for a 3-meter parabolic dish on a motorized azimuth-elevation mount. I need to calculate the worst-case wind torque to size the motors, gearboxes, and brakes. I've heard of EIA/TIA-222 and IEC 61400-2, but I'm not sure which is most applicable for antennas (vs. towers or wind turbines). Do these standards provide drag coefficients (Cd) for parabolic dishes at various angles of attack, and specify how to calculate the torque arm from the center of pressure? Is there a standard wind speed (e.g., "survival" vs. "operational") I should use for motor torque vs. brake holding torque?

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By Jyotsnamayee Nayak Answered 1 year ago

The TIA-222 standard is the definitive code for telecommunication structures in the US. It provides force coefficients for "Parabolic Antennas" (typically 1.2 for the dish facing the wind) and methods to calculate the resultant force location (center of pressure). For torque, you apply this force at the distance from the rotation axis. The standard defines multiple load cases (e.g., operational, ultimate) with corresponding wind speeds. For motor stall torque sizing, use the operational wind speed (e.g., 30 mph) with appropriate safety factors. For brake holding torque, you must size for the ultimate wind load (e.g., 90-120 mph survival speed) to prevent runaway in a storm. Always cross-reference with local building codes, which may govern. Supplement with IEC 60721 for environmental classifications.

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