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Author Topic: Anyone had antenna pole break?  (Read 4267 times)
WH7DX
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Posts: 1029




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« on: May 16, 2013, 11:45:57 AM »

Anyone had a metal antenna pole (snap/break) on them?

I recently raised my Hexbeam antenna up to about 24ft above my flat roof.

I'm using 1.90" galvanized poles for the mount to my CMU block (three large anchor bolts) on the side of the house and as a swivel mount for the antenna pole as well.

The swivel pole is about 4 feet long and bolted at the top of the roof edge with a stainless steel 1/2" (or close to it) bolt with large washers that I bent to semi-circle to go around the swivel pole for added support. 

The swivel pole locks down with another large bolt near the bottom.  So basically, one pole is the anchor, the other is a 4 ft tilt pole to hold the antenna pole.

The 20 foot section of antenna pole is electrical pipe that fits perfectly into the diameter of the 1.90 galvanized.   It's two 10ft sections what are joined with a smaller 6' pipe in the center that is bolted to each side.

The Hexbeam is mounted on the pole (with rotor) and then lifted at an angle and placed into the tilting mount pipe.   The antenna pipe either comes to a stop on the large swivel bolt or another bolt I put in above it to act as the stopper (don't remember).

Once raised and facing the right direction, I drill a hole into the tilting mounting pipe and antenna pipe to lock it in place and keep it from turning.

It's guyed with three antenna ropes in pretty much a triangular degree.

My question is..  It seems strong but it all weighs about 80lbs or so and vertical weight.   If it were to fall the worst it would do is damage my solar water heater nearby.   No electric lines or house damage.   No people nearby etc..

I just reconditioned the whole hexbeam and the next time I do this (hopefully 2 years) - I was going to redo everything and maybe go with a push up pole or crank of some short.  I have salt spray so we'll see.

Suggestions?

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W1JKA
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Posts: 1662




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« Reply #1 on: May 16, 2013, 01:23:43 PM »

Where did your mast snap?
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WH7DX
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Posts: 1029




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« Reply #2 on: May 16, 2013, 01:54:20 PM »

Everything is fine now.   I was just wondering if anyone has any experience with load or metal fatigue - poles etc..

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M6GOM
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Posts: 901




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« Reply #3 on: May 16, 2013, 05:16:59 PM »

I had a 20ft 1.5" diameter ally pole bend just above the top bracket with just a Cobweb on. Same Cobweb is now on a 20ft 2" pole and just fine.

I have another 15ft pole with a 10m Moxon and Yaesu rotator on it and when it gets really windy it sways quite badly.
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WH7DX
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Posts: 1029




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« Reply #4 on: May 16, 2013, 06:56:14 PM »

Thanks.   I was a little apprehensive about putting a hexbeam (that's not that big - but big enough when you feel the energy once it's off balance).. on a pushup pole that comes down to 1.25" - but I probably wouldn't elevate that last section. 

http://www.3starinc.com/30_foot_telescopic_push-up_antenna_mast_ups_shippable.html

My wind usually isn't that bad but it does blow 40mph a couple times a year.   I think the guy rope and anchor is critical and I'm going to increase one of the anchor bolts going into the lip of the roof.   That is way under-rated compared to rope etc - small eye loop with plastic plug.

With the Hexbeam I purchased the larger base mount pole insert which was about 1.75" or so instead of the normal 1.25 or so I believe.

Anyone have any experiences with the plain poles or push up poles?

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LA1BRA
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Posts: 51




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« Reply #5 on: May 16, 2013, 07:10:21 PM »

While not knowing everything about the "pipes" you used, from what I read, it sounds like you used electrical conduit as a mast. Threaded connections....Threaded connections are bad news for mechanical strength, don't do it, Don't use it...however, you did not mention where it broke, at a coupling or where? You can purchase steel pipe in 22 foot sections, less threaded joints, much stronger..Push up poles, well, people use them, I think they are more trouble than they are worth, especially when it comes to guying such a beast, pays your money, wait a few months, go first class, don't scrimp, easier to stay on the air with good grounding and a proper mast to support your wires/aluminum....

regards
xe3/kb5vwz/la1bra/tom
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WB6BYU
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Posts: 13243




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« Reply #6 on: May 16, 2013, 08:08:00 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.
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WH7DX
Member

Posts: 1029




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« Reply #7 on: May 16, 2013, 11:55:22 PM »

While not knowing everything about the "pipes" you used, from what I read, it sounds like you used electrical conduit as a mast. Threaded connections....Threaded connections are bad news for mechanical strength, don't do it, Don't use it...however, you did not mention where it broke, at a coupling or where? You can purchase steel pipe in 22 foot sections, less threaded joints, much stronger..Push up poles, well, people use them, I think they are more trouble than they are worth, especially when it comes to guying such a beast, pays your money, wait a few months, go first class, don't scrimp, easier to stay on the air with good grounding and a proper mast to support your wires/aluminum....

regards
xe3/kb5vwz/la1bra/tom

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.
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WH7DX
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Posts: 1029




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« Reply #8 on: May 17, 2013, 12:02:35 AM »

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.

I can see that.   If something weighs 25 pounds and is extended 15ft it feels like about 200lb horizontal.   I'm wondering how easy it would be to push up a hexbeam and rotor - probably doable with someone else to lock it down every few pushes up to rest etc. 
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W1JKA
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Posts: 1662




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« Reply #9 on: May 17, 2013, 03:04:11 AM »

Re:WH7DX

The mast for my homebrew hex beam is very similar to yours.Two 10 ft. sections of Home Depot electrical conduit 1 3/4 in.od inserted 14 in.into the 2 in. od.pipe with the gap filled with spiral wound medium speaker wire for a tight fit and no slop then through bolted.This is mounted to a 8 ft. 6x6 post cemented 2 ft. into the ground with foam board insulation to prevent frost heave.Mast swivel is 1 ft. down from top of post,just a 7 in.long 2 in.dia.black pipe as a through bolt with flange and 2 U bolts to clamp to mast.Base of mast is 2 ft. up from ground and slips over a 6 in.high pipe mounted vertical on an angle bracket.The mast rotates freely by the armstrong method and locked into position by a C clamp.

Top 20 meter element is about 24 ft. high.Tilting method was originally a 5 gal. cement filled plastic bucket with small block/tackle for a counter weight at mast base,but now have a permanent tag line attached half way up the mast at the pipe joint that I can run a 45 ft. long  small block/tackle from to a tree.This has survived its second winter with Gale force winds and outer edge of Sandy with only slight sway.I believe as others have said that the 20 ft.mast of this type is the limit before bending moments are compromised during tilting.
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W0FM
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Posts: 2055




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« Reply #10 on: May 17, 2013, 08:25:52 AM »

WH7DX mentioned: " I think the guy rope and anchor is critical and I'm going to increase one of the anchor bolts going into the lip of the roof.   That is way under-rated compared to rope etc - small eye loop with plastic plug."

That comment concerns me.  This sounds like a stand-off insulator for 300 Ohm TV twin lead.  These were never intended to be "anchor bolts" for guy rope.  Please don't use it for that purpose or anything else except as it was intended...a stand-off twin lead insulator.  It will not be safe.

Good luck with the upgrade project.

Terry, WØFM
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WH7DX
Member

Posts: 1029




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« Reply #11 on: May 17, 2013, 10:17:04 AM »

WH7DX mentioned: " I think the guy rope and anchor is critical and I'm going to increase one of the anchor bolts going into the lip of the roof.   That is way under-rated compared to rope etc - small eye loop with plastic plug."

That comment concerns me.  This sounds like a stand-off insulator for 300 Ohm TV twin lead.  These were never intended to be "anchor bolts" for guy rope.  Please don't use it for that purpose or anything else except as it was intended...a stand-off twin lead insulator.  It will not be safe.

Good luck with the upgrade project.

Terry, WØFM


Two of the guy ropes (DX Engineering Black 3/8"?) are tied to a fence and totally secure.   The other guy is attached to a small eye loop screw you might hang plants on your ceiling with etc.. driilled into roof, with plastic anchor plug inserted and metal eye screw - screwed in.   

The is the weakness I see.  That should be bigger.   About twice the size and it won't go anywhere.  It currently feels very solid but it just looks undersized now.

Thank you.
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WH7DX
Member

Posts: 1029




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« Reply #12 on: May 17, 2013, 10:25:02 AM »

Re:WH7DX

The mast for my homebrew hex beam is very similar to yours.Two 10 ft. sections of Home Depot electrical conduit 1 3/4 in.od inserted 14 in.into the 2 in. od.pipe with the gap filled with spiral wound medium speaker wire for a tight fit and no slop then through bolted.This is mounted to a 8 ft. 6x6 post cemented 2 ft. into the ground with foam board insulation to prevent frost heave.Mast swivel is 1 ft. down from top of post,just a 7 in.long 2 in.dia.black pipe as a through bolt with flange and 2 U bolts to clamp to mast.Base of mast is 2 ft. up from ground and slips over a 6 in.high pipe mounted vertical on an angle bracket.The mast rotates freely by the armstrong method and locked into position by a C clamp.

Top 20 meter element is about 24 ft. high.Tilting method was originally a 5 gal. cement filled plastic bucket with small block/tackle for a counter weight at mast base,but now have a permanent tag line attached half way up the mast at the pipe joint that I can run a 45 ft. long  small block/tackle from to a tree.This has survived its second winter with Gale force winds and outer edge of Sandy with only slight sway.I believe as others have said that the 20 ft.mast of this type is the limit before bending moments are compromised during tilting.

Thank you for the info.   If you have a picture - send it to my email address in QRZ.  I have a new photo in there of the antenna with an older one as well only 12 ft up etc..

I can see how you wouldn't want to go with 3 sections of pipe and over 20 ft.   It seems strong at 20ft with 2 sections and the inside pipe is overlapping with several feet so that helps.   Glad to hear it's holding up so well.
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W1JKA
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Posts: 1662




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« Reply #13 on: May 17, 2013, 10:54:11 AM »

Re:WH7DX
   
Can't get to your email address,if you want send it to my( Maine) email address located here in eHam and I'll try to send some pic attachments to you.
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WH7DX
Member

Posts: 1029




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« Reply #14 on: May 17, 2013, 11:22:08 AM »

Re:WH7DX
   
Can't get to your email address,if you want send it to my( Maine) email address located here in eHam and I'll try to send some pic attachments to you.

I send you a message.   My email is call sign with @hawaii.rr.com

Thank you!
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