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Author Topic: Tower raising w/ dead man post  (Read 4883 times)
K5KNE
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Posts: 65




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« Reply #15 on: July 04, 2012, 03:00:25 PM »

Tower erecting is a lot of work and prone to accidents.  I rigged a lot of crazy antennas in my past and had some failures some sucesses.

Today with the light cranes and platforms available, I would recommend you just hire someone to stick your tower up when you get everything right on the top and the coax tied to a leg. While they hold it, you can attach your guys and you are through with it and you can enjoy your hamming.

I have seen towers fall, buckle, and antennas break off while raising the tower up from horizontal to vertical. Making a pulling post is a good idea and if you have a hinge and winch your idea should work fine. Get some good advice about just how the pulling post should be set and the winch, cable set up to use. There is a lot of bending moment on the post when the tower load is horizontal. The winch and cable sure needs to be over designed.

Walter  K5KNE
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K5KNE
Member

Posts: 65




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« Reply #16 on: January 17, 2014, 06:28:06 PM »

You might consider just hiring a local crane to come raise your tower and antennas into place and you hook up the guy wires.  Guessing and making something that looks good - may not be safe.  I don't know when you might want to let it down, but calling the crane man back until you can make the needed repairs or changes and the calling him back again to raise it into position   would be a lot quicker and safer than having an accident. Good luck - Walter, retired Professional Engineer
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W9FIB
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Posts: 718




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« Reply #17 on: January 20, 2014, 04:04:36 AM »

Here is what I did. First the actual tower hinge plate is 3/8" steel and tubing and a 1/2" pin that is welded in such a manner that it looks like a door hinge. This is welded to a frame made of 2x2x1/4 angle iron welded as a shelf from 3 2x2x1/4" square tube legs. These legs also have plate welded to the to where I attach a 20' 3 leg home made tower that was once used to support an EME array of 8 boomers, azimuth/elevation equipment, the cross piece to support the spreaders was rohn 20. Estimated at the time to be about 35 square feet of windload and approx. 500 lbs.

The legs and frame assembly are buried in a 6'X6'X6' hole filled with concrete with 1'2" rebar cage built into it and welded at several points to the legs.

This home made tower serves now as my lifting tower.  It is set up so a flat face meets a flat face of the 40' tower that I raise and lower. (When I raise the tower, the lift tower becomes the stop so I can't go past vertical.) I also use a 12V 5000L lb winch to raise and lower. To prevent run away when lowering the cable is wound around a separate drum where I have a brake that I can operate if needed. I also have the lift tower guyed for stability at the top when lifting or lowering. Helps distribute the pull at the top of the lifting tower to the ground.

Now the key point is I have the lift attached at the 20' and the 35' points on the tower. This is made up of 1/4" cable with about 2 feet of slack if the center of the cable is pulled away from the tower. This cable acts as an equalizer to give a better load distribution across the tower. Then my winch line is attached to the equalizer line with a 4" pulley so it can move as needed on the equalizer line.

The point is to make sure what ever you use, it is heavy enough to withstand the loads at any given point of the lift. And to distribute the lift beyond 1 point on the tower to be lifted. Also the system I use uses a lot of extra hardware to make sure the thing can't just take off on its own if something breaks.

You can get a fairly good view of it from google maps street view. Cant see all the details, but between the view and what I explained you should get the idea.
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