Hi,
In U.K. I would guess that a crankup-tiltover tower was more popular than any
other. I
would not care to put a lightweight tribander on top of some of them as I do
not have
too much confidence in their construction. Heavy duty versions were a later
development. My own heavy duty tower is 58 feet tall and rated as follows:
Horizontal headload in pounds
@75 m.p.h @100 m.p.h.
Unguyed 250 145
Guyed 880 880
It is usual in this country to rely on gravity to bring the sections down and
this is
a not uncommon cause of failure. The face width of our most common towers is
very
narrow indeed and as a result, in a moderate wind, the tower sections tilt
slightly,
lock-up and gravity is not able to do its work. When the wind increases the
middle
section (usually) folds. Some of my friends keep ropes to enable to assist
gravity in
these circumstances and thus save their towers. The problem is less severe with
a
wider face on the tower sections.
Another difference would be that most crankups come with a 'head-unit' about
four or
five feet tall which attaches to the top section and contains the rotator. In
order to
accomodate the rotator the face width on this small section is often greater
than that
on the top section of tower proper. Additionally most towers come with some
sort of
ground-post, about six feet tall, about which the tower tilts.
I my case I use 3/4 hp 1400rpm motors driving 80:1 worm gear reduction boxes
which
drive the winches directly. The motors have a very considerable 'safety-factor'
built
in and a power drill would probably do the job.
I do not like climbing!
Enjoy,
Chris
---------------------------------------
Chris Pedder G3VBL/8P9EM
E-mail g3vbl@netcomuk.co.uk
AX25-mail g3vbl@gb7bnm.#45.gbr.eu
DX-Cluster g3vbl > gb7dxd
---------------------------------------
|