[TowerTalk] rotor shelf

[K7LXC@aol.com]

In a message dated 99-04-19 15:18:10 EDT, n1lo@hotmail.com writes:

>  I began pre-assembling (on the ground) the top section of a Rohn 25 
>  tower I am installing soon. I am using standard sections with a flat 
>  top adaptor. I intend to install two rotor plates in the top section, 
>  one for a second thrust bearing (to aid with future rotor servicing) 
>  and one for the rotor itself.
>   Big surprise when I found out that the rotor shelf/accessory shelf 
>  only fits in two places: 1) Joints between tower sections and 2) 
>  inside the top plate adaptor. In both cases, these are places where 
>  there is no bracing. I want to have my rotor about halfway down the 
>  section to give it a longer moment arm, and install the second 
>  bearing just above it. I don't want to waste 10 feet of good mast 
>  just to have the rotor down at the next section joint.
>   After a little head scratching, I grabbed the hacksaw and made one 
>  triangular cutout in the center of each side of the shelf. This 
>  allowed the shelf to fit in the middle of the tower section, halfway 
>  between horizontal braces.
>   Another surprise! the flange of the Rohn TB-3 is too large to fit in 
>  a location that is halfway between two horizontal braces. <jeez>
>   More head scratching....
>   Three more cutouts, one in each side of the shelf, off center, let 
>  me install the shelf just a few inches below a horizontal brace, and 
>  the TB-3 fits, as well. After drilling the hole pattern for it, of 
>  course.
>  
>   Has anyone else had this problem, and how did you solve it?

     That's correct - the situation is the SOP. The accessory shelf is 
limited to placement either at the open place (without diagonal braces) of 
the AG, BPL or BAS sections or the junction between sections. 

     Now that you've got the accessory shelf carved up, where are you going 
to mount the rotator? Only the Ham IV - not the T2X - will work inside the 
25G (except the open places mentioned above). 

     What are you going to be installing - tower height, rotator, mast & 
antennas? If you think you need a second TB-3 (you probably don't - the mast 
isn't going anywhere), are you being too aggressive with 25G? 
>  
>  One more thing. The flat top adaptor (ordered from Texas Towers) 
>  apparently does not come with a set of bolts. Got to get an extra set.
>   The U-bolts that came with the rotor shelves (and tower sections, 
>  for that matter) were thinly plated, not galvanized. They don't look 
>  like they could take exposure to the weather for long. I was thinking 
>  of replacing them with stainless versions.
>   Will these parts benefit from cathodic protection from the existing 
>  galvanizing of the tower itself? Would I be wasting my money on 
>  replacements?

     Rohn miscellaneous hardware is available from Stan at W7NI@teleport.com. 
Cheap, too. The standard hardware in most instances is good enough for me. 

Cheers,    Steve    K7LXC


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