Jim,
A couple of us here in the Detroit area have aluminum towers mounted on
modified boat trailers which use the "falling derrick" method. We use
three-way guying, and one of the guys is the line which pulls the tower up.
Mine carries a 48' tall tower and can be put up by one person using it's
electric winch. K8BB's has a 56' tall tower with a manual winch the
requires considerable cranking, but it regularly lifts a "Christmas Tree"
of 3L monobanders for 20/15/10 for FD, MiQP, etc.
The "falling derrick" method works remarkably well, and when you calculate
the stresses involved for a typical 40-50' aluminum tower with a tribander
or such on top, the loads are pretty reasonable and do not require exotic
materials or methods. YMMV...
73,
Dave/K8CCAt 06:01 AM 6/29/2006, Jim Smith wrote:
>Dave
>
>Google "Falling derrick" Might give you some ideas as to how to put up
>something higher.
>
>A couple of Field Days ago I demonstrated the method. We had a 40 ft
>Delhi tower with an AlfaSPID rotator, an old TH3 tribander, and a
>2m/70cm gain vertical mounted above the tribander. I put the whole
>thing up myself, no climbing. All the youngsters were impressed to see
>that a 70 yr old could do this. (I think that they're also impressed
>that a 70 yr old can remember his own name, making it doubly gratifying.)
>
>Anyway, just a thought. It does take quite a while to rig. The key is
>to use 4-way guying instead of 3.
>
>73, Jim Smith VE7FO
>
>Dave Zeph wrote:
> > We ended up going with 32-foot of tower because
> > 40-feet seemed more that we could "walk-up." The base was anchored at the
> > corners with 4 - 18" "Penetrator" earth anchors from American Screw Anchors
> > that I saw mentioned on the Towertalk Reflector. 3 additional
> "Penertators"
> > were purchased for guy anchors.
> >
> >
> > My long suffering xyl, Diane, and I rehearsed tilting up the tower plus
> > antennas in our back yard. It was obvious that 32-feet was a the limit of
> > our strength, so I bought enough 1/2" Polypropylene rope to rig a 4:1 Block
> > & Tackle, and a pair of Polystyrene Slings. That was the best money spent.
> > We also transported one of those 4-foot collapsible ladders could be used
> > use as both a 13-foot straight ladder, and a 6-foot stepladder.
> >
> >
> >
> > On Friday the first job was to raise the tower. Both of us had spent a
> > somewhat sleepless night wondering if we could do this without loosing the
> > whole assembly. The grass was tall, and moving the stepladder to walk-up
> > the tower was very difficult. However with the 4:1 Block & Tackle, it
> > proved to be a snap. We just walked the tower up to a convenient and safe
> > angle, and then used the Block & Tackle to raise the tower with very little
> > effort. We had dreaded lowering the tower, and that proved to be even
> > easier with the Block & Tackle.
> >
> >
> >
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