The "falling derrick" and the Rohn foldover (that Roger describes)
are different concepts. I have owned both. The Rohn foldover is
better in a confined location. If you have the space, the falling
derrick is more robust mechanically. The critical difference is
that the foldover puts a lot of bending moment on the lever arm.
The falling derrick puts only axial stress on the derrick. This
makes it much stronger as long as you can avoid buckling.
Rick N6RK
Roger \(K8RI\) wrote:
>
>
>
>> There are a lot of windmill monopoles for sale on the web
>> that use this method of tilt up. Suggest you read about
>> them. I've used this technique many times. The "rigging"
>> matters a lot. The other pitfall is that the "stub mast" (also
>> known as a "falling derrick") can buckle. This buckling is
>> encouraged if it sags from its own weight. The fix for this
>> is to put a mid span guy on it connected to the tower.
>
> There were several towers that used this method for "folding over"
> available
> back in the 60s and 70s as I recall. I thought ROHN even offered one at
> some time, but I may be confusing it with a similar set up.
>
> These towers used a truss arrangement that looked almost like an add on to
> the upper portion of a standard tower. This truss extended down almost all
> the way to the base from the hinge point. They used a winch to pull the
> truss down which raised the upper portion. I've seen tubular towers
> constructed in much the same manner.
>
> Triasto I believe was one manufacturer.
>
> 73
>
> Roger (K8RI)
>>
>> One fortunate aspect of buckling is that if the falling
>> derrick is going to buckle, it will do so as soon as you
>> try to lift off the tower. Always lift the tower a foot
>> or so and check for buckling.
>>
>> If you have a big yard, like I do, where you have room to
>> lay down a tower, I highly encourage this methodology.
>>
>> On my web site (www.n6rk.com) there are photos of my 50 ft
>> Glen Martin tower being erected with a falling derrick.
>>
>> Rick N6RK
>>
>>
>>
>>
>>
>> John Tait wrote:
>>>
>>>
>>> Barry Kirkwood wrote:
>>>> Greetings:
>>>> Has anyone experience or comments on non telescoping tilting towers?
>>>> That is: A rigid tubular or lattice mast with a stub mast and hinge.
>>>> In the down posture looks like an assymetrical seesaw.
>>>> Remember years back in a photo in the front pages of QST saw one of
>>>> tubular
>>>> steel maybe 100ft tall.
>>>> In my case have a rugged lattice tower, 6x 10ft sections, wondering
>>>> about
>>>> making it a tilt tower.
>>>> Would value any opinions, reports on experience before I spend money
>>>> on
>>>> calculations by a professional engineer.
>>>> tnx es 73
>>>> Baz ZL1DD
>>>>
>>>>
>>> In one of the old ARRL handbooks, there was a design for a tiltover
>>> tower made of well casing. I've drawn a pic from memory at
>>> http://www.iol.ie/~bravo/Well%20Casing%20Tower.htm. A friend EI9FE,
>>> successfully built a scaled up version of this, in the region of 90ft .
>>> Vy 73
>>> John EI7BA
>>> _______________________________________________
>>>
>>>
>>>
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>>>
>>
>>
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>>
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>
>
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