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Author Topic: Aluminum Towers  (Read 4301 times)
W6UV
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Posts: 536




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« on: August 08, 2012, 10:44:04 PM »

I plan to install a 50' tower and a tri-bander for 20/15/10 and was originally considering a U.S. Towers 55' crank-up model. While researching towers, I came across a company called Universal Towers that sells aluminum free-standing towers.

Based on the specs, the Universal Towers HD-21-50 aluminum tower looks like it might be a better fit for the following reasons:

  • * At $1989 it's $2K cheaper than the U.S. Tower crank-up
  • * It only weighs 190 pounds (spread over five 10' sections), versus >800 for the crank-up, making it a lot easier to get off the truck with fewer people
  • * The base doesn't require a rebar cage, making installation simpler
  • * It won't rust

The HD-21-50 is rated at 21 sq.ft. at 110 MPH, while the U.S. Tower crank-up is rated at 30 sq.ft. at 50 MPH.

The installation instructions for the aluminum tower says to assemble the tower on the ground, attach the antenna(s), and then walk it up. In my case, I don't have 50' of horizontal space to do this. Is it feasible to climb this type of tower and assemble it vertically section-by-section with a gin pole? (Whatever I put up will be installed by a professional tower installer.)

Any reason why I shouldn't consider this aluminum free-standing tower?
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W3DDF
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« Reply #1 on: August 09, 2012, 11:02:44 AM »

I went through a very similar situation as you.  I wanted to get a US Tower MA-40 tower but my county would not accept it because the wind load rating was not what they specified when the tower was extended.  Even after I told them that I would always retract the tower they would not go for it.  I ended up with a Universal 12-40 tower.  I read all the caveats about an aluminum tower but for me that was the only way to go, at least a free standing tower and one at an affordable cost.  I had no problem at all getting a building permit for this tower. Walking the tower up with antennas even if you did have the room is not going to happen.  I hired a local tower installer and he would not climb it.  Just for grins we tried to lift the tower and a 106 lb tower with a triband antenna and Ham IV rotor gets heavy!  I did have the room to assemble the tower on the ground supported by a 6' step ladder near the top to keep the triband elements off the ground.  He made a temporary raising fixture from one section of Rohn 25G, some guys for backguying and a heavy duty comealong.  It actually worked quite well.  We had the tower up with antennas in a matter of a few minutes. Now I am planning on constructing a more permanent raising fixture so I can access the antennas, rotor and perform maintenance on the tower.  I am sure there are other more robust free standing tower but the Universal tower fit into the budget.
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WX7G
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« Reply #2 on: August 09, 2012, 11:13:53 AM »

The HD-21-50 wind rating is guyed, correct?
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AD4U
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« Reply #3 on: August 09, 2012, 12:37:00 PM »

I have two Universal aluminum self supporting towers.  One is 70 feet and the other is 100 feet.  Base sections of both towers are 30" spacing and the tower sections taper in steps from 30" to 26" to 22" to an 18" top section.

I originally installed the 100 footer in 1978 at my old QTH.  It was in about 5 yards of concrete.  In 1989 it survived Hurricane Hugo which came right through here.  I had three each 5 element monoband yagis (10-15-20) on top.  As a precaution I installed one set of guy wires near the top opf the tower.

Regardless of what Universal says, you cannot walk a 60 or 70 foot tower up with antennas etc on top.  Both of my towers have a large power pole installed behind them.  In a pinch I guess you could use a stout tree.  Each power pole has back guys, an electric winch, 1/4 inch steel cable, and a 2:1 ratio block and tackle.  It is easy to raise and lower the towers - just push a button.

When I bought my first Universal tower in 1978, they supplied plated hardware.  Electrolysis between the aluminum tower and the plated steel hardware, "ate" the hardware.  I think Universal now supplies stainless steel hardware.

I am very happy with both Universal towers and would recommend them.

Dick  AD4U
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W6UV
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« Reply #4 on: August 09, 2012, 01:09:41 PM »

The HD-21-50 wind rating is guyed, correct?
No, the wind rating is for the tower free-standing.

I just spoke with Universal Towers on the phone and they say the HD-21-50 is rated for 21.08 ft2 at 110 MPH.

I have too big concerns with this tower. The first is erecting it. I have no room to raise the tower with it in its fully assembled 50' configuration, with or without antennas on it. It will require erecting it one section at a time using a gin pole. If this is not possible, then this tower is a no-go for me.

The second concern I have is how much twisting torque this tower can withstand. While winds anywhere approaching 110 MPH are extremely rare around here, we do commonly get sustained 40-50 MPH winds. A tri-bander with a 32' boom, like a KT36XA, can put a lot of twisting torque into the top of the tower via the mast. Is this kind of tower likely to survive this?
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AD4U
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« Reply #5 on: August 10, 2012, 11:22:41 AM »

As I stated above my 100 foot Universal tower survived Hurricane Hugo in 1989 with 100+ MPH winds.  I was afraid to look out when the sun came up after the hurricane passed.  Many trees were down but the tower was still standing.

There were three 5 element mono band yagis on top.  The 20 meter yagi was on a 46 foot boom.  The 10 and 15 meter yagis were on shorter booms.  The 2 inch ID schedule 40 steel mast was bent about 20 degrees from vertical, but the tower survived.

Once again as a precaution I had one set of three guy wires spaced 120 degrees running from near the top of the tower to 6 foot long screw in power pole type anchors.  The guy wires probably saved my tower.  I understand guy wires are not an option at your site.

If you spec the tower properly I do not think you will have any problem with a long boom tri band yagi.

Dick  AD4U
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WB4AUW
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« Reply #6 on: August 10, 2012, 04:41:16 PM »

Universal Towers makes quality stuff. Go by the specs and directions provided by them and you won't have any trouble.
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W6UV
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« Reply #7 on: August 10, 2012, 06:44:40 PM »

Universal Towers makes quality stuff. Go by the specs and directions provided by them and you won't have any trouble.

Their directions say to assemble the tower sections horizontally on the ground, attach the antenna(s), and then walk the tower up. I can't do that because I don't have the room around the tower due to many obstructions near the ground. I need to be able to erect the tower vertically section-by-section or it just won't work for me.
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W9GB
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« Reply #8 on: August 10, 2012, 08:17:20 PM »

Quote from: W6UV
Their directions say to assemble the tower sections horizontally on the ground, attach the antenna(s), and then walk the tower up. I can't do that because I don't have the room around the tower due to many obstructions near the ground. I need to be able to erect the tower vertically section-by-section or it just won't work for me.
Option #1 :
GIN POLE, EXPERIENCED TOWER CLIMBER, and GROUND CREW

Option #2 :
CRANE, EXPERIENCED OPERATOR and GROUND CREW
« Last Edit: August 10, 2012, 08:21:25 PM by W9GB » Logged
KC4MOP
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Posts: 729




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« Reply #9 on: August 11, 2012, 04:15:43 AM »

Quote from: W6UV
Their directions say to assemble the tower sections horizontally on the ground, attach the antenna(s), and then walk the tower up. I can't do that because I don't have the room around the tower due to many obstructions near the ground. I need to be able to erect the tower vertically section-by-section or it just won't work for me.
Option #1 :
GIN POLE, EXPERIENCED TOWER CLIMBER, and GROUND CREW

Option #2 :
CRANE, EXPERIENCED OPERATOR and GROUND CREW

IF you are going with the 50 footer (good choice) then OPTION #1 from W6UV would be less strain on the tower. 50 feet will start flexing and possibly bend the tower out of shape trying to lift all of that metal to the vertical position.
30 feet::: you might be able to pull it off but not 50.

Fred
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KG4RUL
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« Reply #10 on: August 11, 2012, 04:27:06 AM »

Just a thought - If you send a climber up the tower, where does he place his feet while climbing?  After all, this is an Aluminum tower.  I think that the manufacturer's recommendation for walking up the tower from the ground is made for just that reason.
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WB4AUW
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« Reply #11 on: August 11, 2012, 01:03:56 PM »

You climb the Universal towers just like you would any other tower, with your feet on the cross supports. I climbed mine to do antenna work quite a few times and worked on my neighbor's 60 footer. They are very sturdy and strong.
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AD4U
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Posts: 2153




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« Reply #12 on: August 12, 2012, 05:57:51 AM »

I climbed my 100 footer MANY times.  Sometimes it is easier and quicker to climb it to fix a simple problem than to tilt it over.

BTW I bought my 100 footer in 1976 or 1977 and it is still going strong.  About 15 years ago I changed the original plated steel bolts with stainles steel hardware supplied by Universal.  This is supposed to eliminate the dissimilar metal electrolysis problem.  So far so good.

Dick  AD4U
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N1BIL
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« Reply #13 on: August 13, 2012, 10:01:20 AM »

I  just bought a 40ft Universal tower from another Ham who was moving. It had withstood the Desert winds well.
Now for the rest of the story, verify that your City will accept the  Universal Mfg. installation information in the manual. I had to order a $400 set if stamped engineered drawings for the city. I just got a call from the city saying they are needing more engineering information (wind calcutions for 100 MPH winds). I will be sinking more money into a tower than the tower it's self cost.  I'm only putting  a six sq. foot antenna (wind load) and an additional 2 sq for the rotor and mast on top of the tower. I HIGHLY RECOMMEND: GET A COPY OF THE MANUFACTURES PRODUCT MANUAL INCLUDING INSTALLATION REQUIREMENTS. TAKE THEM TO YOUR LOCAL CITY OR COUNTY AS APPROPERIATE. VERIFY THEIR NEEDS AND REQUIREMENTS BEFORE PURCHASING ANY TOWER. 
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AD4U
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Posts: 2153




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« Reply #14 on: August 13, 2012, 12:57:36 PM »

I  just bought a 40ft Universal tower from another Ham who was moving. It had withstood the Desert winds well.
Now for the rest of the story, verify that your City will accept the  Universal Mfg. installation information in the manual. I had to order a $400 set if stamped engineered drawings for the city. I just got a call from the city saying they are needing more engineering information (wind calcutions for 100 MPH winds). I will be sinking more money into a tower than the tower it's self cost.  I'm only putting  a six sq. foot antenna (wind load) and an additional 2 sq for the rotor and mast on top of the tower. I HIGHLY RECOMMEND: GET A COPY OF THE MANUFACTURES PRODUCT MANUAL INCLUDING INSTALLATION REQUIREMENTS. TAKE THEM TO YOUR LOCAL CITY OR COUNTY AS APPROPERIATE. VERIFY THEIR NEEDS AND REQUIREMENTS BEFORE PURCHASING ANY TOWER. 

Or move out of the city into the country as I did 15 years ago.  HI!

Dick  AD4U
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