Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: Prev 1 [2]   Go Down
  Print  
Author Topic: Anyone had antenna pole break?  (Read 4405 times)
W0FM
Member

Posts: 2055




Ignore
« Reply #15 on: May 17, 2013, 01:04:31 PM »

Bryan,

Understand the attachment screw now.  Its a plastic "molly"-type anchor with the screw threaded into it, not a plastic insert in the eye of the screw.  Thanks for the clarification. Either way, you are correct to beef it up.

WØFM
Logged
WH7DX
Member

Posts: 1029




Ignore
« Reply #16 on: May 17, 2013, 02:47:16 PM »

Anyone know of a really solid tilt mount base for up to 2" pipe?

The one on DX Engineering is for small stuff...

Trailer Jack doesn't have a long enough pole - put maybe.
Logged
WH7DX
Member

Posts: 1029




Ignore
« Reply #17 on: May 19, 2013, 02:56:07 PM »

It seemed like we bent a push-up mast every year on Field Day when someone
tried to extend it on the ground and tilt it up that way, especially with a beam
on top.  The forces involved in tilting it up often exceed the forces due to wind,
etc.  A better way to put it up is to leave the mast telescoped as much as
possible, tilt that up into place with the beam on top, guy the top of the first
section, then push up each remaining section while standing on a ladder.

In the new issue of QST there is an article on the forces of lifting an antenna vertical from a slightly elevated holding position.

Based on lifting with rope from the balanced point of a 192lb tower (mast / antenna) the lifting pressure equals 658lbs of pressure if the tower is initially lifted 7 feet high or 16 degrees off the ground.

So if my Hex beam on 20ft galvanized pipes weighs 100lbs and I have it 7ft up in the air and then walk it up it has 342lb of pressure on lift side (which I'm not sure if that is the same as the push side?)   That's why I was asking my sons if the Hexbeam was stuck on something at about 30 degrees up in the air.. it seemed unusually heavy, like a guy rope was stuck.

In the article they have  192lbs x (1 / 16.26 degrees) = 192 x 3.428 = 658lbs.    (I don't know how (1/ 16.26 degrees) = 3.428???



Logged
KF5RGB
Member

Posts: 16




Ignore
« Reply #18 on: May 20, 2013, 06:01:36 AM »

Quote from: WH7DX
It's not threaded pipe.   It's sold at Home Depot in the same area as the wire.   I know what type of threaded pipe you are talking about.  This is the pipe they use and bend and carry wire.   It appears to be the same thickness as the galvanized fence pipe - about 1/16.

Nothing broke.  Just wondering about others experiences with this stuff and push up poles etc.

If it's not threaded it has to be that cheap thinwall EMT, that stuff will bend easy and easily break at the coupling where it joins, very bad choice for an antenna pole.  Being an old electrician if I was going with electrical pipe I'd go with rigid, or even better yet some that good heavy duty water pipe that comes in 20 ft lengths.
« Last Edit: May 20, 2013, 06:05:21 AM by KF5RGB » Logged
WB6BYU
Member

Posts: 13288




Ignore
« Reply #19 on: May 20, 2013, 07:12:38 AM »

Quote from: WH7DX

This is the pipe they use and bend and carry wire...




And therein lies one of the potential problems:  thin-wall conduit is DESIGNED TO BE BENT,
which limits its strength.  It may also have a fairly weak seam along one side.

That's not to say that it won't hold up an antenna, but it won't be as strong as something
that is designed for structural use.

If you have to tip up something like that, use a gin pole of some sort, or the "falling derrick"
method, so you have some support for the end of the mast as it goes up.

Some friends in Russia put up a 120' vertical for 160m using a triple falling derrick:
first they put up a 25' post, then used that to raise a 55' post, which then pulled up
the final vertical.  It had a few kinks in it, as they dropped it 3 times in the process,
but once they got it up it was quite effective.  I think there is video of it somewhere,
but I don't have the link handy.  (If you use that method to put up a beam, put the
tower/mast up FIRST, get all the guys shorted out, then lower it, put the beam in
place, and raise it again.)
Logged
W5WSS
Member

Posts: 1735




Ignore
« Reply #20 on: May 20, 2013, 09:30:37 AM »

Hello correct do not walk it up.....have the proper hardware for guy and everything ready then telescope it up the prescribed amount for each section then anchor it using the proper guy rope kit and stake anchors....When done right the system will work within the designed capability.
The structural integrity of such a system should never be compromised but rather followed to exactly installation recommendations provided the manufacturers instructions....But to ease your loads avoid walking it upwards from a pre extended technique.
73
Logged
WH7DX
Member

Posts: 1029




Ignore
« Reply #21 on: May 20, 2013, 11:40:33 AM »

Quote from: WH7DX

This is the pipe they use and bend and carry wire...




And therein lies one of the potential problems:  thin-wall conduit is DESIGNED TO BE BENT,
which limits its strength.  It may also have a fairly weak seam along one side.

That's not to say that it won't hold up an antenna, but it won't be as strong as something
that is designed for structural use.

If you have to tip up something like that, use a gin pole of some sort, or the "falling derrick"
method, so you have some support for the end of the mast as it goes up.

Some friends in Russia put up a 120' vertical for 160m using a triple falling derrick:
first they put up a 25' post, then used that to raise a 55' post, which then pulled up
the final vertical.  It had a few kinks in it, as they dropped it 3 times in the process,
but once they got it up it was quite effective.  I think there is video of it somewhere,
but I don't have the link handy.  (If you use that method to put up a beam, put the
tower/mast up FIRST, get all the guys shorted out, then lower it, put the beam in
place, and raise it again.)


Only the inside pipe the makes the joint and overlaps about 3 feet inside the two 10ft galvanized pipe is electrical conduit.   

This is a sample of the galvanized pipe and it's 16 gauge 1.7 thick so that's good.

Funny thing is..  two of the comments out of 3 mention a weather station and TV antenna - not a fence  Grin

http://www.homedepot.com/p/YARDGARD-1-5-8-in-x-1-5-8-in-x-8-ft-Galvanized-Metal-Line-Post-328923DPT/100322474#.UZptCeDnv9E


(What's up with the math on the Lift Weight in QST - message above.    I must be missing something)
Logged
WB6BYU
Member

Posts: 13288




Ignore
« Reply #22 on: May 20, 2013, 12:40:31 PM »

Quote from: WH7DX

In the article they have  192lbs x (1 / 16.26 degrees) = 192 x 3.428 = 658lbs.    (I don't know how (1/ 16.26 degrees) = 3.428???



Because it is missing the tangent operator:

( 1 / tan( 16.26 degrees ) ) = 3.428
Logged
KF5RGB
Member

Posts: 16




Ignore
« Reply #23 on: May 20, 2013, 02:59:39 PM »

Quote from: WH7DX


Only the inside pipe the makes the joint and overlaps about 3 feet inside the two 10ft galvanized pipe is electrical conduit.   

This is a sample of the galvanized pipe and it's 16 gauge 1.7 thick so that's good.

Funny thing is..  two of the comments out of 3 mention a weather station and TV antenna - not a fence  Grin

http://www.homedepot.com/p/YARDGARD-1-5-8-in-x-1-5-8-in-x-8-ft-Galvanized-Metal-Line-Post-328923DPT/100322474#.UZptCeDnv9E

Your link is for a 8' chainlink fence post not electric pipe, here is a link to 1 1/2 EMT, that's what you probably used...........

http://www.homedepot.com/p/Allied-Tube-Conduit-1-1-2-in-x-10-ft-Electric-Metallic-Tube-Conduit-101584/100400412#.UZqb4KLVCfU

Logged
WH7DX
Member

Posts: 1029




Ignore
« Reply #24 on: May 20, 2013, 03:41:18 PM »

Quote from: WH7DX


Only the inside pipe the makes the joint and overlaps about 3 feet inside the two 10ft galvanized pipe is electrical conduit.  

This is a sample of the galvanized pipe and it's 16 gauge 1.7 thick so that's good.

Funny thing is..  two of the comments out of 3 mention a weather station and TV antenna - not a fence  Grin

http://www.homedepot.com/p/YARDGARD-1-5-8-in-x-1-5-8-in-x-8-ft-Galvanized-Metal-Line-Post-328923DPT/100322474#.UZptCeDnv9E


Your link is for a 8' chainlink fence post not electric pipe, here is a link to 1 1/2 EMT, that's what you probably used...........

http://www.homedepot.com/p/Allied-Tube-Conduit-1-1-2-in-x-10-ft-Electric-Metallic-Tube-Conduit-101584/100400412#.UZqb4KLVCfU




In my first post.. I wasn't very clear in what I was using.   I mentioned all the poles and what I used as the mount and swivel mount pipe.  I made it sound like I was using the electrical pipe as the main antenna mast.  I'm not.  I'm using the 1.9" galvanized fence post and I'm using about 5-6 feet of electrical pipe that is the perfect diameter to fit snug into the galvanized pipe and used at the joint (overlapping and bolted down).

That link is the electrical pipe I was using as the joint.  I see the 10ft section weighs a little over a pound (seemed heavier than that), where the 8ft fence pole was about 7lbs (thick stuff).  

That fence post is good cheap stuff and for us in Hawaii, shipping is a big concern for large items.
« Last Edit: May 20, 2013, 03:50:04 PM by WH7DX » Logged
KG4NEL
Member

Posts: 373




Ignore
« Reply #25 on: May 21, 2013, 06:56:12 AM »

Only time I've seen a metal pole fail was during the teardown of an 80m 1/4-wave vertical. With about 50' left in the air, someone on the guy lines stopped paying attention...

That was before I started running regularly, still managed to move rather quick  Tongue
Logged
WH7DX
Member

Posts: 1029




Ignore
« Reply #26 on: May 21, 2013, 12:55:26 PM »

Quote from: WH7DX

In the article they have  192lbs x (1 / 16.26 degrees) = 192 x 3.428 = 658lbs.    (I don't know how (1/ 16.26 degrees) = 3.428???



Because it is missing the tangent operator:

( 1 / tan( 16.26 degrees ) ) = 3.428

I think I got it now..    The TAN value for 16.26 degress = about 0.29  so  1 / 0.29 = approx. 3.428

For those in the KNOW - is the Lift Power Needed = to the Push Power?    
Logged
KC8VWM
Member

Posts: 3119




Ignore
« Reply #27 on: May 25, 2013, 01:52:29 PM »

Quote
That's not to say that it won't hold up an antenna, but it won't be as strong as something
that is designed for structural use.

<snip>

Only the inside pipe the makes the joint and overlaps about 3 feet inside the two 10ft galvanized pipe is electrical conduit.   

This is a sample of the galvanized pipe and it's 16 gauge 1.7 thick so that's good.



Ahh yes, the usual confusion about pipe vs. tubing...

"Pipe" is similar in context to "Hose," which is typically intended for transferring fluids, or gases which build internal pressures. However, "pipe" is not rated or intended for use where structural strength is required.

"Tubing" is intended to provide structural support. For example, engineers use structural tubing to design and construct buildings, bridges, towers and other support structures where structural strength is a specific requirement.

The weight or "heaviness" of the black pipe, is not in any way an indication of it's structural strength. In fact, if you stand a long section of black pipe on it's end, you will notice it will bend over like a noodle. So basically the wall thickness doesn't much matter.

Pipe is very flimsy compared to tubing because "pipe" is intended to transfer fluids while "tubing" is intended for supporting structures.

For example you might notice aluminum tubing, such as the kind they use to construct antenna booms is very lightweight, but yet very strong and rigid. Guess that's why they call it "structural tubing" as opposed to calling it "pipe." Such as the reason why PVC "pipe" is a poor choice for situations requiring structural strength. So take some time to google and learn about their ASTM/ANSI structural differences and intended specifications.

..
Logged
WH7DX
Member

Posts: 1029




Ignore
« Reply #28 on: May 25, 2013, 03:29:42 PM »

When I hear "tubing" I associate a large black donut with some water....    Grin

Usually, I do my certified strength test at the store...   I grab the center of the pipe/tube and shake it violently to feel for any flex...   Grin

But seriously, thank you for the explanation of the difference.   That's the 2nd or 3rd thing I learned today.    I also learned that in 1983 the FCC said you didn't need to maintain log files anymore. 
Logged
Pages: Prev 1 [2]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!