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UfMIVERSAL MIAIMUFACTURIIVG CORPORATIOIM
<br />•2357 East 3 Mile Rcl. Warren. Michigan ^BOB9 13131 774-4I4Q
<br />The Standard RS-222-A ia ultra-conservative in its apeclflca-
<br />tlon of wind loadings of 30, Uo, and 50 pounds per square foot.
<br />This conservative approach resiata not from its choice of design wind
<br />velocities but from its specification of "A nominal value of K (for
<br />presaxirea on the projected areas of flat surfaces) is .OOU.” Hence
<br />the wind pressure is P « K or P « O.OOUv^. The coefficient in
<br />that equation depends directly upon air density. In our past calcu
<br />lations we have used the value of 0.00256 which is based upon so
<br />called ''standard conditions" (I50 Centigrade (59® F), 76O sn Hg).
<br />Perhaps thia is less conservative than is desirable. If we assume a
<br />temperature of -Uo® F, the density of the air then yields a coeffi
<br />cient of 0.0031. If we use this coefficient and the wind velocities
<br />(87, 100, 110 mph) inferred in the Standard we arrive at pressures
<br />of 23.U, 31»0, and 37.5,pounds per square foot for the loading zones
<br />A, B, and C respectively. It is my opinion that it is entirely
<br />reasonable and prudent to offer towers based on these wind pressures
<br />even though they do not comply with the Standard RS-222-A.
<br />Accordingly, given below are effective antenna areas based on
<br />factor of safety of 1.67 based on a minimum yield of 35,000 pounds
<br />per square inch:
<br />30 Foot Tower A B . C
<br />11,11,1U 2.75 1.25 0.50
<br />11,14,18 6,75 4.50 3.25
<br />1U,18,18 8.25 5.25 3.75
<br />14,18,22 15.50 11.25 8.75
<br />w 4o Foot Tower
<br />11,14,14,18 2.50 1.25 0.50
<br />I ■■ -5.
<br />» '■ ■ ^ .14,14,18,18 4.25 2.00 1.00
<br />H 11,14,18,22 6.75 4.50 3.25
<br />14,18,18,22 8.25 5.25 3.75
<br />14,18,22,22 10.5 6.50 4.50
<br />14,18,22,26 15.50 U.25 8.75
<br />50 Foot Tower
<br />11,11,14,18,22 2.75 1.25 0.50
<br />11,14,18,18,22 4.25 2.25 1.0
<br />11,14,18,22,26 6.75 4.50 3.25
<br />14,18,22,22,26 10.50 6.50 4.25
<br />14,10,22,26,26 11.0 6.50 4,0
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