I can address the placement of the rebar cage. The normal method is to
put the cage on top of concrete blocks. Those blocks will raise the
cage above the bottom of the hole and remain in place as you pour the
I'm installing a TX-472 at my QTH. The hole is dug and I've been
"battling" the local permit people. The documentation they want is now
"on order" and should be here in a couple weeks.
I may install a second tower someday and the Aluma tower certainly is
attractive to me. If I hadn't found this used TX-472 locally I probably
would have purchased the Aluma.
No need to attach the screws to the rebar. I don't know if the screws
are bent over at the bottom but if they aren't you should put nuts on
them so the bolts can't pull out of the concrete. You may want to bolt
them to the "T" plate and level the plate before pouring the concrete.
The plate should be supported to/from the concrete form and held in
place securely so it won't move when the concrete is poured. Be sure to
either vibrate or use a length of 2x4 to force the concrete to flow into
all voids. Also, ask the person pouring the concrete to go slowly so
the flow doesn't move the rebar cage. The concrete truck can pour so
fast the cage will be moved. The cage should be held in place so it
can't move. I plan to use Stainless Steel aircraft safety wire to hold
the cage in place. I've got quite a bit of 0.040" safety wire left from
an airplane I built a few years ago....
Krishna Kanakasapapathi wrote:
> Hello all,
> I am in the process of installing an Aluma crankup. I have the permit on
> hand and am following the specs.
> My handi man is helping me with the work.
> The tower has a "T" base plate. The Tower hinges to this plate. The "T" plate
> is expected to be fixed with
> 5 screws in concrete.
> Here are the questions i have.
> a) Does the Screws have to be attached to the rebar cage?
> b) Is Zinc plated screw good( from home depot). I think not, since it has to
> be galvanized. The "T" plate is
> c) If the screws have to be attached to the rebar cage, i can see that the
> holes in the "T" plate to receive
> the screws do not align well with the rebar cage vertical members. This
> would mean that i would need
> some kind of a plates to hold the screw using bolt/nuts. At least 2 plates
> per screw to hold it.
> d) The handiman is proposing to hold the rebar about 3 inches off the ground
> ( per spec) using 2x4 and then
> as the concrete is poured in, he wants to remove it. I am afraid of this
> proposal. I have seen other tower
> installation pictures where the entire rebar cage is held by 2x4 with nuts
> holding the screw all the way up
> from the "T" plate.
> Please let me know.
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