Crankup-tiltover towers

Chris Pedder
Tue, 06 Aug 1996 22:09:40 -0700


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!


Chris Pedder	G3VBL/8P9EM
DX-Cluster	g3vbl > gb7dxd