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

[Alan NV8A]

On 12/31/12 01:48 am, Larry Loen wrote:
> 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.

I have one of those every-which-way ladders (similar to the Little 
Giant, but mine is a no-name generic bought years ago), which, in its 
inverted-V configuration, works fine.

73

Alan NV8A