[TowerTalk] temporary guys
Dick Green WC1M
wc1m at msn.com
Sat Dec 16 12:05:46 EST 2006
> The guys are to be at 31, 61 and 91' according to the drawings.
Alternatively, you could put the top guys at 95'. According to the Rohn
catalog, that would raise the specs on the tower from 90 MPH to 110 MPH. It
would also put your top guys only 5 feet below the top plate.
> Questions: First, is there a "strong" reason not to guy at
> the 100' level, when all that is going up is the access
> point, it's directional antenna to the backhaul, and a small
> omni-directional antenna?
If that's all you'll ever put on the tower, probably not. Having some space
between the top guys and the top of the tower can make it a little easier to
tram large antennas to the top. I guess one could ask, is there a strong
reason not to guy at the Rohn-specified levels? I understand you might be
reluctant to climb 9 feet above the guys, but I can assure you that this is
not a big deal. It may be a tad wobbly, but nothing to worry about. The
tower sections are designed for it (see below -- you can climb up 30 feet of
unguyed sections above the last guy point when erecting the tower.) As I
pointed out above, if you're worried about it, put the top guys at 95' and
you'll still be compliant with Rohn published specs.
> Second...what about temporary guys when putting it up. If we
> don't use them, he'll be up on 3 sections of unguyed tower,
> which just doesn't seem right ;). What material should we
> use for them?
The tower sections are heavy-duty enough that you can climb at least 30 feet
above the last set of guys. If your base is sunk in the concrete, that
provides enough rigidity to climb at least 30 feet of unguyed sections as
well. But if you use the pier pin base, you must use temporary guys. Many
people put the two bottom sections together, attach the temporary guys to
the top of the second section, "walk" them up to the vertical, and lift them
onto the pier pin. That's possible with Rohn 45 (about 70 lbs per section),
but I found it's not really feasible with Rohn 55 (100 lbs per section.) So
I used temporary guys on the first section. I added a second set of
temporary guys to the top of the second section as well (see below.) Once I
got the permanent guys installed at 33', the temporary guys were no longer
Rohn says the temporary guys should be made of steel. I know that many hams
use heavy-duty rope for temporary guys. I think you would want to be sure
that the knots are tied properly in that case. I used 1/8" stainless steel
guy sets from an AB-577 portable military tower because I had them on hand.
The breaking strength of the stainless guys was certainly adequate to the
job, but I did worry a bit about whether the "snubber" pressure clamps would
hold. That's the reason I used two sets of temporary guys. In any case, you
should use the concrete-embedded permanent guy anchors to secure the guys if
you can. In my case, one of my uphill anchors was actually above the top of
the bottom section, so I had to use AB-577 screw anchors about 30 feet from
the base to secure that section. I used the concrete-embedded anchors to
secure the temporary guys on the second section.
In my case, the better part of four tower sections were stacked above each
permanent guy point, and I had to climb either 33 or 35 feet above the last
guy point to install the next set of guys. It was a little scary, but Rohn
45 and 55 are beefy enough to handle it structurally.
73, Dick WC1M
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