UST already makes crank up towers with safety locks installed at the top of the
1st section only.
They appear to be made of 1 inch thick plates, two such plates used at each
corner. A pull rod
runs down the side of the tower to grnd level. Short rods are installed
between the 3 x corners
at the top of the 1st section. When the pull rod is pulled down, the 3 plates
swivel and lock the
tower into place. This feature can be used at any height from fully nested
to fully extended.
However they can’t be engaged just willy nilly. The tower has to be in
specific locations so cross bracing
is not in the way of the safety lock plates. The upper sections do not
require the safety locking plates, since the
upper sections all use one steel raising cable PER FACE !! IE: 3 x lift
cables for EACH of the upper sections.
The only way the upper sections can collapse is for all 3 x lift cables on any
given section to break simultaneously.
While the tower is being raised or lowered, the single lift cable from the
winch drum is holding the entire tower up.
IF it broke while raising or lowering, the tower will collapse. However,
once the tower is raised to XXX height, and
safety plates are engaged, the load is then taken off of the main lift cable
on the drum. At that point the upper sections
can be guyed in most cases, since the upper sections have 3 x lift cables per
section.
You have to be careful you don’t leave a ton of slack in the primary lift cable
in any of these safety plate schemes. Too
much slack, and the lift cable could jump the pulley.
My own HDX-689 does not have the safety lock feature. However, the upper
sections do have 3 x cables per section
( except for the very top section, which only has 1 lift cable. ) . To make it
safe foe climbing, a steel section of
2 inch tall x 6 inch wide x .25 inch thick rectangular steel tubing can be
inserted just below the bottom of the 2nd section.
Some have also used 4 x4 or 6 x 6 wooden posts for this application. Up to 3
can be used.
Jim VE7RF
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