At 04:02 PM 6/26/2006, Kelly Johnson wrote:
>Outriggers would be preferable, but guys would be acceptable if necessary.
>
>Here's another thought. Would it make things easier or harder to
>assume that the tower will be transported by an SUV or truck whereby
>the bed of the truck or the roof of the SUV could be used to hold the
>tower for transportation. Remember, the whole goal here is to make it
>possible for me to transport and erect the tower by myself.
This is what I was contemplating with my 50 foot mast/flagpole hooked to
the car roof rack idea. It's very doable (take a look at what the Kite
Assisted Photographer/Pole Cam guys are doing). Actually, this works even
better than the tower trailer, because it gets your pivot point up high, so
you can have your mast almost perfectly balanced. Then, you can climb up
on the roof to attach the antenna, once the mast is vertical.
Think of the rigs used to push a rowboat,scow, canoe, raft, kayak up on the
roof rack. (the ones that don't require you to lift the boat up over your
head) A couple rollers and an extending member so that the pivot clears
the rear (or side) of the car. You slide the tower back until about 6 ft is
hanging over the pivot, tip it up, and you're done. I've seen a clever
design for sea kayaks and canoes that sort of moved diagonally, so that the
hatch could still open.
The problem I've found is wind survival. You either have to be willing to
tolerate a collapse in fairly moderate winds, OR, deal with the
outrigger/guy/ballast issue. The roof rack just isn't strong enough to
take the side loads. {Lesson learned: Do NOT attach guy lines to the roof
rack!, not only does the rack fail, but it also deforms the roof with it,
which makes it expensive to fix.} In any case, design so that a collapse
destroys something cheap to fix, not your car.
W4EF has erected a 50 foot-ish mast for the 160 contests anchored to his
truck several times. His comment is that you need to bear in mind the wind
loads when tipping up. With a crankup/telescoping tower this wouldn't be
such a big deal.
http://www.dellroy.com/W4EF's-Ham-Radio-Page/Salton-Sea-05/Salton-Sea.htm
http://www.dellroy.com/W4EF's-Ham-Radio-Page/Stew-Perry_El-Mirage/El-Mirage.htm
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