[TowerTalk] [Tower Talk] Designing a "receiving cradle" or jack stand for my HDX 572MD US Towers tilt over

[Larry Loen]

One thing that US Towers "leaves to you, the consumer" is designing some
sort of gadget to receive the tower's weight when it tilts over.  I don't
think there is a standard term, so I have started calling it a "cradle"
because it will "cradle" the tower when it is tilted over, thus protecting
both the tower and the crank over wire.

Terms of art might be "jacks" or "floor jacks" or "jack stands" or similar.

I can't remember what the W0IBM design had (except that it had one for a
very similar tower).

My thoughts:

1.  The tower plus all attachments will be under 2000 pounds.  I figure the
device should be able to support 2500 or 3000 pounds to provide some margin
of safety in the design.

2.  I would like there to be some kind of flexibility at the point of
contact such that the tower has a fairly broad contact with the cradle.  I
don't want the tower's outside legs of the tower to be carrying the whole
tower's weight on maybe 1/2 inch of metal contact surface.  That seems
needlessly risky.  Something several feet long makes intuitive sense, but
it needs to have some amount of adjustability; it should tilt, at least a
little, in the same plane the tower "rotates in" when it drops to account
for variations in positioning the cradle, soil settling over time, etc.
The most obvious design for that will require some sort of very special
bolt or rod and metal braces of similar strength so that these can transmit
the entire weight of the tower to the rest of the cradle.  This would allow
me to have multiple heights as well as I anticipate several working heights
and do not always want to be on a ladder at the "rotor" end of the tower as
I will be when the big boom is installed but not when it is not and I am
servicing things like the rotor, the thrust bearing, etc.

3.  Similarly, I presume that I want something (reinforced plywood, a metal
plate, something) of a couple of feet long to spread the weight of the
tower as it contacts the ground.  Soil is very sandy here so it again makes
intuitive sense to spread the load.  I don't want the tower to "pile drive
in slow motion" in terms of driving some metal rod into the ground, even if
it is over time.

4.  The ideal "legs" for the cradle would be adjustable so that I could
have the tilt over be at different heights (e.g. with no antenna installed;
with my existing KT36A installed, to name the two I now must concern myself
with).  This could be similar (but a bit stronger) than some of the kind of
automobile "stand".  An 3 ton version is seen here:
http://www.harborfreight.com/3-ton-heavy-duty-jack-stands-38846.html   but
these are too short.  I figure it should stand from about four to eight
feet.  But, the picture shows the kind of adjustability I have in mind as
far as the stand goes.  Or, maybe something similar to this:
http://www.northerntool.com/shop/tools/product_200331730_200331730   It
goes from a foot and a half to three feet, but it handles the weight with
ease.

5.  I also need something an aging ham or hams can carry from my shed to
the tower site (maybe a walk of 75 feet, total).  So, the low weight of the
"floor jacks" seems to be close to what I need.

The last link is probably closest to what I have in mind.  So, I'm
thinking: Like a floor jack, but with some ability to provide substantial
surface contact area at something other than 90 degree angles, taller, but
doesn't need to carry so much weight.

What do you guys use and why?

Keep in mind that some of the clever "tilt plate" approaches on the antenna
itself may be difficult to deploy.  I am currently planning to have a KT
36A at the base and A3WS at the top end of the mast.



Larry Wo0Z