Hi Dan,
I did exactly what you're considering for my 38' Telex tower and it worked out
great. I used a 1/2" steel plate with 1/2" x 3" x 10" steel bar for the
uprights. I bent the uprights (had them bent actually) at about the 4" point
and drilled the 2 corresponding holes in the longer side to match the tower
legs, being careful to keep everything square and equal distance from the
base. Next, I temp. bolted the uprights to the tower and then clamped the base
to the uprights and then drilled through the uprights and base, forming the
holes for the anchor bolts. Next, I securely bolted the uprights to the base
and then removed the whole unit from the tower, took it to a welder and had a
bead welded on both sides of each upright to keep everything in alignment.
Since the base is square and the tower triangular, I put an additional anchor
bolts in the corners that the single side is on. This gives me a total of 5
anchor bolts. I made a plywood template of this base to assist in holding the
bolts while pouring the concrete. It worked out just fine. Remember to allow
enough thread above the base for a bottom nut and for adjustment. In
retrospect, the 1/2 for the base is probably a major overkill. The uprights
actually take the load and the base simply holds the whole thing together. I
bought my steel from a scrap yard and they charge by the pound so I could have
saved a few bucks using lighter gauge steel on the base. Adjust any dimensions
to allow for your larger tower. Your idea of basing it on the US Tower design
sounds like a good idea to me. Have fun. Use a Force 12 or Hygain 40 meter
beam. Avoid Cushcraft, they screwed me and other early buyers of the X9.
Good luck. 73's
Jim
WB6YAW
Dan Levin wrote:
> Learned friends,
>
> I am about to install a used Hygain HG70HD 70 foot heavy duty (relatively
> :-) crank up tower. I plan to install a 6 sq. foot 4 element TET tribander
> just above the top of the tower, and some kind of ~5 sq. foot 2 element 40
> meter yagi about 10 feet above that. My soil is very heavy clay, with a
> rather solid sandstone below that. I don't know whether my tower base will
> reach into the sandstone or not, and I won't know until I dig the hole.
>
> The HG70HD base is designed with three "feet", made of steel bar stock
> something like 1/2" x 2" x 8". These "feet" have 3 3/4" holes drilled in
> them. The design is to bury matching pieces of stock in the concrete, with
> ~10" sticking up into the air, and then mate each pair together (the piece
> that is welded to the tower and the piece that is buried in the concrete)
> and connect them with 3 3/4" bolts.
>
> This seems like a perfectly reasonable plan, but it does not allow for any
> leveling of the tower after the concrete is poured. The "feet" sticking out
> of the base have to be plumb - if they are not that is tough luck.
>
> Now, I am an engineer by training, and I hate designs that lack mechanisms
> for adjustment. I have seen the U.S. Towers base design, and it is the same
> with one small but critical difference. Instead of bolting the feet
> directly to mates buried in the concrete, the U.S. Towers bases bolt the
> feet onto a steel plate, which is in turn suspended on three anchor bolts
> that stick out of the concrete. This allows full adjustment for plumb,
> since the plate can be raised or lowered relative to any of the three bolts
> by simply turning the nut that the plate rests on. This seems like a much
> better design to me.
>
> So, I have a couple of questions.
>
> 1) Can anyone explain to me why the original Hygain design, which lacks
> adjustability, it better than the U.S. Towers design?
>
> 2) If not, can anyone help me to calculate the size of the base plate and
> the anchor bolts that I would need to use a U.S. Tower style base for this
> tower?
>
> 3) If not, can anyone tell me the size of the base plate and anchor bolts
> used on the U.S. Towers TX-472 or HDX-572? These towers are of similar
> size, weight and height to my Hygain, so it seems reasonable to use the same
> size base components (no?).
>
> Thanks much,
>
> ***dan
> Dan Levin, N6BZA
>
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