![]() I also use a thimble with each guy wire connection, so I don't think chafing would be a problem no matter how much the cables sway in the wind. I use guy brackets, but without the torque arms. A tower holding a few inverted vees has a cake walk life.ĭon: Do you use guy brackets on your tower to interface with the guy cables at each level or are you connecting directly to each tower leg? Your chafing comment got me wondering. Pushing a tower to its torque limits with stacked 40M or 75M rotary Yagis means closer spaced guys that are more accurately adjusted. Though, much will depend on the load the tower holds. I agree with Don that 1/10th (600 pounds) is too darn tight. Those guys have quite a bit of droop and still are probably close to 300-400 lbs of pull. I have some guy anchors that are out about 190' from the tower. The should whip around a little when you swing them by hand, but not too much. But the "RF invisible" feature for higher band Yagis is quite nice with Philly.īTW, I adjust my guy wires by look and feel. I've always used steel EHS here with insulators for Rohn 45, 1/4" cable, and use homemade star guying with large torque arms (6 guys) at most levels. How have you found Phillystran to be for stretching? Does it need to be tightened periodically about the same as EHS? What size are you using, the 6,000 lb stuff? If I did adjust mine to 10% of breaking strength, I'd try to do it on the coldest day of the year. I think the best approach would be to do a compromise, maybe by adjusting them to specs in the autumn or spring, when the temperature is about midway between normal extremes for your area. Some tower people recommend readjusting according to the season, but that seems like a lot of extra work for nothing. I adjusted mine to be slightly loose in summer and still not too tight in the coldest weather. I can see a big difference in mine between hot summer weather and sub-zero winter. The tower has been up for almost 30 years now, and I see no signs of wear or fraying at the attachment points, which is supposed to be the reason to keep them that tight, to minimise movement when the cable sways. It is said that you are supposed to tension the guys to 10% of breaking strength, but when I tried that to the best I could measure it, it seemed too tight to my liking, so I loosened them up just a bit. ![]() The NAB Broadcast Engineer's Handbook explains how to do this in order to get consistent results for each guy level. I tightened the turnbuckles on one set until they seemed reasonably tight but not too tight, and observed the sag, then used that as a standard to go by for the rest. I did mine on my tower simply by eyeballing it. ![]() You might be able to borrow one from someone who does tower work. It seems to work well enough for small cables, but it is not consistent when I try to read 3/16" EHS cable. I have one, but don't trust it because I don't get consistent readings. There is a gadget called a dynomometer that works on the above principle, but does it automatically by just clamping onto the guy wire. You might find the specific formula in a textbook somewhere. The tension will be proportional to the amount of force required to displace the cable. Then at the midpoint between the contact points use a spring scale to displace the cable a specific measurable distance. If you can find the formula, one method is to place some sort of rigid frame next to the cable, that touches the cable at two points a known distance apart.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |