So much for DY0566 RESET...

[Wintertime]

I guess it's time for Plan B for KFI, whose new tower fell down yesterday:

 

http://www.ocregister.com/articles/tower-r...1491-tall-clear

 

This was a replacement for the one that got taken out by a small plane in 2004. That station was DY0566.

 

I see that some geocacher logged it as found just last year. I guess he saw the shorter backup tower and figured that was it--despite Klemmer's very clear description of its demise in 2004. I've had the same problem with HT2630, which someone logged after I explained that it was destroyed in the 1989 Loma Prieta earthquake. Sigh...

 

Patty

[andylphoto]

Sad to see. For radio/tower geeks like me, here are a couple links with lots more pictures from a local ham radio operator. He was actually on site when the stick fell, and has a photo of it falling. And for the benchmarker in each of us, note the last photo in the construction series.

 

Tower construction:

http://www.k6rix.com/kfitower.html

 

Tower damage:

http://www.k6rix.com/kfitowerfalls.html

[monkeykat]

that's a neat photo of the damaged towers from the quake (HT2630). Gotta imagine they got a pretty good oscillation when that was going on. Thanks for the link Wintertime.

[+piper28]

Ok, the curious part of me wonders why these towers built like this all have a pointy bottom end. I'm sure there's some logical reason (and I suspect even without the pointy end it wouldn't add any real stability for something that tall), but I have no clue what it is. Anyone know?

[+Klemmer]

So if it falls over, you can stand it up again either way up?

 

BTW: My offices are almost across the freeway from where the old KFI tower was, and we were VERY glad to see it go. The interference on the whole middle AM band was ridiculous. I had already sent a complaint to the FCC (for what good it did - none). Unfortunately, some folks had to die to bring it down. Sad. I sure hope they do a better job of interference mitigation on the new one - if they ever get it built again, and they get it to stay up! Sheesh!

Edited March 20, 2008 by Klemmer & TeddyBearMama

[andylphoto]

Ok, the curious part of me wonders why these towers built like this all have a pointy bottom end. I'm sure there's some logical reason (and I suspect even without the pointy end it wouldn't add any real stability for something that tall), but I have no clue what it is. Anyone know?

 

I'm not a tower engineer, but here's my thought. On a guyed tower, there's nothing about the tower that keeps it straight, but rather the tension on the guy wires. having a single point of contact at the base would offer less resistance when adjusting tension on the guy wires than having it sit on all three legs. This particular tower was to be 684 feet. If the first 20-foot section was even a fraction of an inch off plumb when it was placed, imagine that error multiplied over the length of the tower. Along the same lines, if it were just sitting (i.e. not bolted to the concrete pad) you would also face the possibility that in tensioning the wires to plumb the structure, you'd have a majority of the weight supported by only one leg. Again, I'm not an engineer, but my suspicion is that this would weaken the whole thing. Having a single point of contact would help mitigate that.

 

Additionally, since KFI is an AM station, the tower IS the antenna. That being the case, there's an insulator between the tower and the ground.

[Wintertime]

Here's what someone told me:

 

"The tower base 'point' is rounded, and sits in a concave recessed place at

the center of the top of the insulater, so it can move about slightly with

the natural sway of the tower. Were it bolted, it could crack the insulator."

 

I suspect that Andy's theory about it being difficult to even out the pressure on all the legs is a consideration, too.

 

Patty

[+KX6D]

I'm not only a tower fan, but I'm a Geocacher too...

http://www.geocaching.com/profile/?guid=39...40-d1f40b232fb6

 

I'm glad you liked my pictures. In one of the construction photos, you can see my Del Tack cup on the OLD base insulator.

 

The tower does move in the wind and when the ground shakes. Its designed to. Yes, there is an insulator at the base because the entire tower radiates. As pointed out already, it IS the tower.

 

The base on this tower was flat. You can see a picture of my hand grabbing it.

 

If you have any questions, I'd be glad to answer them.

 

Dino - K6RIX

[Bill93]

I believe the usual tower spec, after guy wire adjustment, is less than 1 part out of line horizontally for each 400 parts of height. It might be more during construction or under wind loading.

[+Klemmer]

Hey Dino, long time no talk! Who let you into the Benchmark forum? If you're out at the KFI tower again, give me a call & drop over to my office! I'll PM you my office number.

Klemmer

(Larry K)

[andylphoto]

I'm not only a tower fan, but I'm a Geocacher too...

http://www.geocaching.com/profile/?guid=39...40-d1f40b232fb6

 

I'm glad you liked my pictures. In one of the construction photos, you can see my Del Tack cup on the OLD base insulator.

 

Dino - K6RIX

 

Hey Dino,

 

Thanks for checking in here! Thanks for posting the great pictures, and sharing the information. Great to see you post here.

 

What I've been wondering since I saw your pictures was if you were a part of the tower crew or contracting for KFI somehow, or how you had such great access to the site for photos? Are you able to elaborate at all on the failure that caused the fall?

 

73,

 

Andy

KB8PPE

Edited March 25, 2008 by andylphoto