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Old 10-08-2009, 08:31 AM   #2
JB Antennaman
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Join Date: Jun 2009
Location: Pennsylvania
Posts: 1,409
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One of the differences between just being able to put up a antenna and knowing what you are doing - is experiencing what you just experienced.

Usually the antenna rotor housing is made out of aluminum and is strong enough that you can measure down from top to bottom and divide that in half and then measure side to side and divide that in half and then drill a #7 or 13/64ths hole. Usually in the inside of the rotor housing there is a web there that strengthens the housing without adding extra weight.

If you hit that web dead center, you can then tap that hole with a 1/4 20 tap. I do it while the mast pipe is already mounted to the rotor.
I then clearance drill the pipe to accept a 1/4 - 20 bolt and I put that through the mast pipe with a flat washer on the end of the bolt and I put a nylon lock nut and another flat washer on the outside of the rotor housing.

That should be all the more you should have to do to keep the orientation of the rotor in a exact position.

Usually the mounts on the side of the rotor are strong enough that all you need to do is put a wooden dowel in the mast pipe going up to the rotor to keep it from crushing when you tighten the clamp to keep it from rotating on the pipe.

I then cover the top of the pipe with a piece of Polyken 226 tape and tape that with some Scotch brand 3 M electrical tape to keep the water out.

The problem with the mast pipe, can usually be solved by using a better quality pipe.

As I advised before, if you have access to someplace that builds racecars or a steel shop that sells race tubing. You can get some chrome moly or DOM tubing - .125 wall 1 1/2 or even .095 wall - 2 inch tubing.

The problem then becomes - is the mount strong enough to take the wind load the antenna gives it.

Putting a thrust bearing above the rotor will solve some of your flex problems, but sometimes the contricity or eccentricity of the cheaper tubing - causes binding problems and does not solve the problem - it only causes more problems. That is why I stay away from electric weld and only use seamless tubing.

DOM - drawn over mandral - extrudes the pipe and takes out some of the kinks - while making the pipe straighter and stronger. But with a cheap rotor, there is usually so much slop in the rotor bearings that it does not matter much.

The real problem in the rust belt areas is freezing in the wintertime.

Usually the good thrust bearing costs more then the rotor its self.
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