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, csudds@probe.net (Chuck Sudds)
>>writes:
>>
>>> 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
KT-34XA
>>> 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
>internet: dquick@mm.com
>Compuserve: 75526,2656
>wd0ekl@wb0gdb.#stp.mn.usa
>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
that!)
73 de Bob - K0RC
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