Hi all,
Let me begin by informing you that I am fully aware of the K7LXC
Prime Directive.
I am making plans for the top section, rotor, mast and thrust bearings
in a new Rohn 25 installation. The mast will be about 18-20 feet long. The
rotor will be mounted at the bottom of the top section. One thrust
bearing will be mounted on the flat top. A second thrust bearing will be
mounted on a plate 24 inches below the flat top. With this setup 10-12
feet of the mast will extend over the top of the tower for mounting antennas.
Future serviceability of the installation is on my mind as I complete this
design. Here are some thoughts:
1. If an antenna breaks, it can be removed directly for repair,
2. If the rotor breaks, it can be removed directly for repair,
3. If a thrust bearing breaks what do I do?
Let's talk about the upper thrust bearing. Removal process would for a
bearing mounted on top of the flat top would be to remove all antennas and
slide the bearing up and off the top of the mast. Ugly process.
The lower bearing is mounted on the top of a plate inside the tower. Removal
would require sliding both the plate and the bearing down to the rotor and
removing them there. Somewhat ugly.
After all that discussion, here's the idea:
Why not mount the thrust bearings on the UNDERSIDE of each of the
mounting plates? The Rohn TB-3 appears to operate just fine upside-down.
I'd use big, wide washers on the top to help distribute the downward
forces across the mounting plate. Wouldn't this substantially ease the removal
of either thrust bearing? Taking the upper bearing off by bringing it
down to the rotor sounds much more appealing than taking it off over the top!
Okay . . . let me know everything that's wrong with this idea . . .
73,
Jim K1IR
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96 Morse Road
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email jimi@designet.com
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