Dale L. Martin wrote:
> Huh?
>
> You are up on the second or third section of a crankup....the
> cable lets go. What the hell good is it going to do you at all
> to have your hands, fingers, feet, and toes OUTSIDE the tower
> rungs while the section you are on has a section plummeting
> inside and as your section plummets towards the outer base
> section? Where are your hands and feet, then?
>
> Helllllllooooooooooo.......
>
> Kurt, I can't believe you are saying this.
Hi Dale,
I knew someone would question this. Sounds pretty scary eh? Well, it
certainly can be!
Further explanation is required.
First off, I don't let the sections I'm on go plummeting anywhere! If the
inner sections are going to fall, I'm going to tell them where to stop.
Remember, the discussion was about climbing a properly blocked crankup
tower. I never climb an unblocked crankup, unless it is sitting at full
collapse, with the cable slack.
Second, I always thought that one was supposed to assess any tower before
climbing it! If the tower condition suggests old age and opportunity for
failure of any components, the climber is supposed to say NO!
The crankup blocking can't be safely done at extensions beyond 1/2 way
without the use of external equipment or on towers with small sections
with narrow clearances between section faces, or light duty towers that
have whimpy bracing.
The basic idea is to never be on unblocked sections, and always have
blocks in place to stop the possible fall of inner sections as high as
possible. The best place for them is on the top of a section as the
horizontal top braces are usually the largest and have the most weld area
to the legs. The towers I've done this on had huge 4" and 6" channels for
the top horizontal braces. I wouldn't try it on some of the small cheezy
ones.
Here is a description of what I have done twice on a HD472. I did
something similar on a more extended 72 but that was a very new tower and
every move was not completely safe. I just concentrated on minimizing the
risk exposure. Wouldn't have done it on an older tower. When does
climbing a tower pose NO RISK?
Bring tower down to just a little above 1/2 height. This height was
required by the circumstances, lower is better.
I've used 2"x2"x1/4 wall steel box tube 1 1/2-2" round steel and 4x4 and
4x6 timber for blocking. I like the steel box tube the best.
Place the blocking tubes through the 1st section just below the bottom of
the second section in all three corners and let tower down till the 2nd
section is hard on the blocks. I installed the first blocks from a step
ladder. Then I put blocks through the tower just above the top of the
first section to stop potential falling sections here. These blocks were
installed from an extension ladder leaning against the 1st section big
top horizontal brace.
So before getting on the tower the bottom of section 2 is blocked and
there are loose bars sitting through section 2 on top of section 1 to
stop section 3 & 4 falls.
>From the extension ladder get onto the tower at the top of the first
section. Put feet on top of the base section legs (it can't possibly
collapse anywhere!), lanyard around the second section, which is blocked
twice and will not fall. Put blocking tubes through tower below the
bottom of section 3. I am tall and can insert them 8' above the top of
the next lower section. This is usually just below the bottom of the 3rd
section.
Then lower the tower some more till the bottom of the 3rd section is hard
on the blocks to lock it to section 2.
So, after standing on the tower the first time, 3 sections are blocked!
If section 4 falls it has to get past the blocks at the bottom of section
3 to stop at the blocks on top of section 1.
Climbing to the top of the second section is the hardest. It needs to be
done mostly by hand. The only thing in the tower while climbing is hands
on the braces, feet are on the outside of the legs of the blocked
section. The large towers have plenty of clearance between the bracing
of nested sections to clear my fingers. I've found that it is possible to
get foot support on at least one face by placing a toe on a properly
oriented diagonal brace. I look carefully to see that the boot is not
into the tower more than an inch or so. I climb this section on the
corner, hand gripping braces on the two adjacent faces, with blocking
tubes tied to belt.
When I get to the top of the second section, I put the bars in above the
top of the second section. So section 3 now has two sets of blocks and a
section 4 fall will stop at the top of section 2. Then position myself
standing on the top of the second section legs. Pull more blocking tubes
up from ground and insert them at the appropriate location under the 4th
section. Then lower tower til the 4th section is hard on the blocks.
At this point all sections are blocked, the cable goes slack, and nothing
is going to collapse anywhere. The wind may blow it over, but I usually
get off the tower at 30-40 Mph.
After each section is blocked, the same number of turns on the winch
result in more nesting of the upper sections. This makes the subsequent
blocks to get lower and easier to reach.
I don't recommend it for anyone, specially when other options are
available. I've only done it on 4 section towers. I wouldn't want to do
it with more sections. It is obvious that the lower the tower is nested,
the easier it becomes.
I haven't had to do it for several years. My upper body strength isn't
what it was then. I've never done it on a tower with cable older than 5
years.
It is a slow painful procedure that has to be very carefully thought
through, and done in a very deliberate manner.
The times I did this were for cable feed problems on the winch drum. The
cable positioning lead screw got so far out of sync with the drum, that
the thing couldn't be fully collapsed. We had to get the load off the
cable to get the equipment apart and straighten out the mess.
An easier situation would be to use a bucket and the same blocking
procedure. Being in a bucket, underneath the antenna is just as risky if
the thing collapses, so the blocking procedure, is still necessary.
Maybe, the bucket can be positioned to clear the antenna, like, in
between elements. But, this is rarely possible if the tower has stacked
antennas.
Another way, my favorite if material is available, is to install a
stacked tower to the face of the base section with plenty of u-bolts. We
did this when high winds bent the mast on one of my Dad's 472's, big
christmas tree on top. We put the stacked tower up with gin pole just
like normal. With 20' of the thing attached to the base section and 20'
extended, it was very stable. We used some of my Rohn HW (35). We were
able to find an azimuth that made the side tower clear all elements. Then
went up and dropped antennas til the mast was bare, then pulled it with
the gin pole and put the new mast in.
The side mounted tower was so handy, it stayed there for several years
(because I didn't need it) to make working on the antennas easier.
This side mounted tower would have been ideal for climbing and blocking
the fetched up cable problem. Just didn't have it at the time!
Like I said, I agree with Steve, K7LXC, I'll climb a blocked crankup if I
block it, or have been there when it was blocked!
YMMV!
BTW, I also agree with Stan, W7NI, there are no plans to put a crankup
here! That's because I don't want to, but mainly because I'm not forced
to.
73, Kurt
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