In a message dated 97-03-09 20:07:37 EST, n3rd@ix.netcom.com (Dave Hawes)
writes:
> Unfortunately, the holes in the plates are
> not large enough to pass the bolt from the clevis, so merely
> repainting the existing plates is not an option.
Hi, Dave --
Why not wire brush them and then use one of the rust converter
products? It'll react with the rust and neutralize it while putting a tough
coating on the steel. Before you do that, drill out the holes so that it
will take an appropriate clevis then you don't have to replace ANYTHING.
Personally, I'd rather not make any more work for myself than I have to.
BTW, TOWER TECH has the Rustoleum Rust Converter ($8.00 for 8 ozs.).
>
> The issue of safety in this project is two-fold:
>
> 1. Detaching the existing guy wires, one a at a time, to do the
> work on the attachment plates, and
> 2. Unbolting the plates and replacing them.
>
> As to Issue #1, I believe that the AB-105 tower is robust enough to
> withstand this kind of maneuver. In fact, I have detached one top
> guy wire many times to allow my large yagis to pivot down to the
> tower using a "PVRC (tm) Yagi Mount." I see no reason why removal
> of intermediate guy wires, one at a time, should present any
> significant danger, but am interested in opinions. Of course, the
> work would be done in calm wind conditions to minimize the potential
> for buckling forces.
You'll want to slack off the remaining guys on the same level while
leaving them attached because you don't want to put unnecessary forces on the
other tower legs.
>
> Regarding Issue #2, it is important to note that guy attachment
> plates mount on top of the splice plates at each tower juntion.
> Replacement of the plate requires unbolting half of the bolts at the
> splice!
>
> Concern: Structural stability of the tower. Probably not a worry,
> since the splice plate has six more bolts holding the joint stable.
>
> Concern: Settling of the tower section. This is my real fear. I'm
> not so sure that the tower sections are actually butting. I think
> that the bolts at the splice plate are in shear and taking most or
> all of the dead weight load of the tower. If I take the bolts out,
> even of just half of the splice plate, especially at the 47 foot
> level, and the tower settles, I might not be able to get the holes
> lined up again. In that event, I can visualize (in my nightmares)
> having to jury rig some kind of jack to separate the tower sections
> far enough to get the bolt holes lined up. (I'm pretty sure a drift
> pin would not have the mechanical advantage needed for the job, but
> then again it might.) This would not be able to be done right away,
> and the tower could be left in a dangerous condition for some period
> of time while a workaround is developed. Not a happy thought.
>
> I would appreciate any insights other owners of or maintainers of
> AB-105 tower might be able to provide on this subject. I'm hoping
> my fears as described above are merely overreaction, but better safe
> than sorry. I fully realize that this is a very, very narrowly
> focused question, and apologize for the bandwidth. However, this
> reflector is a great resource, and I figured it was worth a shot,
> especially since this is essentially a safety related issue.
>
The leg joint brackets are very substantial and will keep things intact
enough that you should be able to remove half of the bolts to replace the
brackets. Loosening all of the guys will minimize the downward compression
forces on the legs while still providing enough tethering to hold the tower
up. Refinishing the existing brackets will avoid this problem completely.
Your drift pin is all you need to get the holes lined up again. Pound
it in with a hammer and then you'll be able to put most of the bolts back in.
Don't forget that the bolts go OUT through the legs so you can secure the
nuts on them. It looks like there's less than 1/8 inch gap between the
sections of my AB105 so you're not talking about a lot of movement.
73 and GL, Steve K7LXC
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