I shouldn't really call it a falling derrick, I suppose.
What I use is just a prop to keep the cable high enough to give lift when
the tower is low. Our FD tower actually starts below horizontal, since the
base is on the tail of the trailer and the top is on the ground, or maybe on
a block. Then we raise it enough to install the A3 beam. When the tower is
up about 30 degrees, the cable from the front of the trailer to the top of
the tower is getting pretty high and the prop falls away. That's fine,
since the system is very stable at that point.
----- Original Message -----
From: "Richard (Rick) Karlquist" <firstname.lastname@example.org>
To: "Wilson Lamb" <email@example.com>
Cc: "firstname.lastname@example.org" <email@example.com>
Sent: Thursday, February 02, 2012 1:26 PM
Subject: Re: [TowerTalk] Question about lowering a Fold-Over tower
> On 2/2/2012 7:48 AM, Wilson Lamb wrote:
>> Worse yet, if you get the least lateral displacement you will get the
>> off to the side of the hinge/tower plane and you will then have the top
>> the tower trying to go sideways because of the cable pull being off axis!
>> You can tear your hinge apart and wreck your beam in a heartbeat>
> In my early days of experimenting with irrigation pipe verticals I
> encountered this problem, but it just wrecked some old tubing.
> Glad I didn't learn this on a tower. You really want to side guy
> the tower if possible.
>> The falling derick advice is right on, BUT you have to be sure the base
>> the derick is wide enough to provide the lateral stability you need to
>> prevent the off center situation above. AND you have to secure the cable
> I prefer to side guy the falling derrick. Again, I experienced early
> on the consequences of not doing this.
> I always mount a pulley at the top of the derrick and run the rope through
> it to a ground anchor located where the pulley hits the ground. This gives
> me positive pull down when the tower is near vertical, and controlled
> descent. If you just tie a rope to the
> top of the derrick, you have no leverage when the tower is near
> Rick N6RK
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