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Re: [TowerTalk] Trouble mounting T-2X

To:, "Tower and HF antenna construction topics." <>
Subject: Re: [TowerTalk] Trouble mounting T-2X
From: "Roger (K8RI)" <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Sat, 20 Mar 2010 15:39:29 -0400
List-post: <">>

w4lde wrote:
> Started to mount a new T-2X purchased on 3/3/10 yesterday.  Made up all 
> of the plugs and checked the rotor out on the ground at the tower.  
> Rotor worked properly on the ground
> Dropped the tower and tilted it over so we could install the rotor body 
> and mast.  We checked the bolts and the tower mounting plate for the 
> correct mounting and they aligned OK.  The rotor plate is heavy duty 3/8 
> to 1/2" thick and welded in place.
> I had only insert the mounting bolts in the body a few turns before 
> taking it outside and didn't notice anything unusual.  Used some anti 
> seize lube' on the bolts.
#1 question. Are you sure the thread size and count is the proper one?  
(IE 5/16 bolt IIRC and NF or NC thread) Are you sure the threads in the 
rotator body are proper and complete. As N6FD questioned, are you sure 
there are no shavings left in there. Double check to verify what the 
bolt size and number of threads *should* be.  If necessary find some one 
with a thread gage and make sure what you have is what you want/

If the bolt threads and body holes  are the same size (and count, or 
threads per inch) the bolts should turn in freely, all the way by hand. 

It's not uncommon to find bolts with threads that are not full depth, or 
with the wrong threads per inch even when the bolts are the proper 
diameter and holes with only partial threads or threads that only go 
part way through. In the old housing the holes went all the way through 
with full threads.  There are both National Fine and National coarse 

If necessary you may need to run a finishing tap into the threaded holes 
in the base of the rotator. This is something that should be done with 
the rotator disassembled (you don't want metal shavings running around 
in there)  and only as a last resort after you have proven the threads 
in the body have not been cut to full depth.

73 and good luck,

Roger (K8RI)

> My helper (brother) did notice that the rotor body bolt holes seemed a 
> little out of the pattern and very close to one edge, however, when 
> aligning the body to the rotor plate they look almost dead on.  So we 
> proceeded, then the trouble started.
> The mounting bolts turned in hand tight about a 1/4 of the way in, not 
> free at all and got to the point (1/4 way) that we decided to use my 
> small ratchet set.
> Not even 1/2 way in the bolts started to seize and we were very 
> reluctant to proceed.  I checked the depth of the holes in the body and 
> they are free in equal to the length of the bolts.
> We backed out the bolts and lowered the rotor to the ground and again 
> tired to insert and screw in the bolts while free of any mounting plate 
> with the same results.
The difference between NF and NC with 5/16 bolts is enough you should 
only be able to get a couple threads turned in before they'd bind.  Now 
if one set of threads is metric and the other American then  it would be 
possible to have a much closer match.

When it comes to rethreading and particularly in cast Aluminum it's very 
easy to end up with too little thread left to have much if any holding 
>   It almost seems like the threads are not right 
> for the mounting bolts or the bolts are two long 
The bolts should screw all the way into the casting unless they've 
changed the design.
> but we didn't want to 
> over tighten. The bolts were in a plastic package so I assume they were 
> the correct ones supplied by the factory.
> Looks like we did slightly bend one bolt head and not sure when that 
> occurred but I can always get a new bolt locally.
> Any ideas?  Your input and help will be appreciated.
> 73 de
> Ron W4LDE
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