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[TowerTalk] New T2X

To: <>
Subject: [TowerTalk] New T2X
From: (Robert Chudek)
Date: Sun, 30 Mar 1997 00:25:31 +0000
At 12:45 PM 3/29/97 -0600, Dave Quick WD0EKL wrote:
>At 11:52 AM 3/29/1997 -0500, Steve K7LXC wrote:
>>In a message dated 97-03-29 11:29:34 EST, (Chuck Sudds)
>>> I just received my new T2X rotor from Norm's and have bench tested it and
>>>  everything works just fine. I will be installing this within the next week
>>>  in my Rohn HDBX48 with top thrust bearing. I will be rotating my KLM
>>>  Tri-Bander and a small 2M beam. I am installing new 8-wire rotor cable at
>>>  the same time. The cable run is only about 80ft.
>>>  My question is:  Is there anything else that I should do before installing
>>>  this new rotor? 
>>      Well, yes.  The T2X will fit but won't rotate in the BX series of
>>towers without some modifications.  The case ears that stick out on the T2X
>>are the culprits.  One thing you can try is to bend out the X-braces at the
>>rotator.  This is from the 'bigger hammer' school of tower construction.  The
>>other thing that you can do is to remove the rotator shelf and re-install in
>>upsidedown.  This apparently gives you the clearance you need.  I haven't
>>tried it personally but this tip comes from Bill, W7TI, and is worth a try. 
>>73,  Steve  K7LXC 
>I know that a T2X won't fit in a BX-2 top section because a Ham IV just
>barely fits,
>but it might fit in a BX-3 top section. 
>Depends on how the tower is configured. I believe an HDBX-48 is sections BX-8 
>through BX-3, with BX-8 being the largest available base section.
>Dave Quick WD0EKL
>Compuserve: 75526,2656
>Grid square EN35jb
>Minneapolis, MN

Dave you are correct, the HDBX-48 uses sections BX-8 through BX-3.  The
Rohn drawing A-760001 states the following wind load specifications for
the various combinations of BX-1 through BX-8 tapered tower sections:

Allowable antenna load for 20 psf (70.7 mph) with antenna mounted 3 feet
above the tower apex and a boom length of 10 feet or less:

Height  Sections used      Rohn model     Area ft^2   Thrust lbs
  24    BX-1,2,3              BX-24           6           120
  24    BX-2,3,4             HBX-24          12           240
  24    BX-3,4,5            HDBX-24          20           400
  32    BX-1,2,3,4            BX-32           6           120
  32    BX-2,3,4,5           HBX-32          12           240
  32    BX-3,4,5,6          HDBX-32          18           360
  40    BX-1,2,3,4,5          BX-40           6           120
  40    BX-2,3,4,5,6         HBX-40          10           200
  40    BX-3,4,5,6,7        HDBX-40          18           360
  48    BX-1,2,3,4,5,6        BX-48           6           120
  48    BX-2,3,4,5,6,7       HBX-48          10           200
  48    BX-3,4,5,6,7,8      HDBX-48          18           360
  56    BX-1,2,3,4,5,6,7      BX-56           6           120
  56    BX-2,3,4,5,6,7,8     HBX-56          10           200
  64    BX-1,2,3,4,5,6,7,8    BX-64           6           120

To help identify the BX sections here is a chart of the center
line width from leg to leg for each section at it's widest end:

Section       Width
BX-1           9.53 inches
BX-2          11.86 inches
BX-3          14.20 inches
BX-4          16.58 inches
BX-5          19.23 inches
BX-6          21.89 inches
BX-7          24.56 inches
BX-8          27.41 inches

These dimensions are from the center of the channel to the center
of the adjacent channel so measuring with a tape on the outside of
the structure will produce a slightly higher number.

The concrete base specification is for 3,000 psi minimum ultimate
strength concrete and were designed for 2,000 psi soil.  The bases
range from slightly under 2 yards^3 to almost 5 yards^3.

So there's just about everything you might want to know at a glance
about this popular Rohn product used by many amateur radio operators.

Well, okay... a little more?  Upright legs are ASTM A-446 Grade C
steel (minimum yield point 45,000 psi) galvanized according to
ASTM A-525.  Braces are cold rolled C-1017 steel (minimum yield point
36,000 psi) also galvanized to ASTM A-525.  Leg splice bolts are
SAE Grade 5 steel.  And last but not least (this holds the whole 
thing together!), rivets are 2017-T4 aluminum alloy.  (I never know

73 de Bob - K0RC

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