[TowerTalk] TowerTalk Digest, Vol 128, Issue 80
Jack Berry
we5st at yahoo.com
Thu Aug 22 10:39:33 EDT 2013
If you could be certain that no one could possibly get hurt when the cable fails you can 'do nothing'.
Of course you must also be able to absorb the cost of replacing the tower and all the mounted parts (antenna, rotator, etc) when it fails.
Otherwise you can replace the cable yourself for $200, which is really cheap by the way. Or you can leave the tower down.
On Aug 22, 2013, at 2:21 AM, towertalk-request at contesting.com wrote:
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> Today's Topics:
>
> 1. Re: Question on mast height above tower (Gene Fuller)
> 2. Re: Question on mast height above tower (Brian Alsop)
> 3. Re: Rohn HDBX 40 - mast length (K7LXC at aol.com)
> 4. Re: Rohn 45AG4 guy tabs? (K7LXC at aol.com)
> 5. Re: Penetrox/Noalox vs. Anti-seize compound (K7LXC at aol.com)
> 6. Re: Question on mast height above tower (K7LXC at aol.com)
> 7. Different Type UHF Female (rfman45)
> 8. Thoughts on Tower lifting cable broken strands (Ray Benny)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 21 Aug 2013 13:56:36 -0400
> From: "Gene Fuller" <w2lu at rochester.rr.com>
> To: <TexasRF at aol.com>, <RShirbroun at newportlabs.com>,
> <towertalk at contesting.com>
> Subject: Re: [TowerTalk] Question on mast height above tower
> Message-ID: <1538A6204DB34730A31827368E143B0B at FamilyRoom>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=original
>
>
> These numbers looks like calc's for bending moment at the top of the tower.
>
> What about torque ?
>
> Would it be possible to put the rotor plate lower in the tower and pick up
> some extra restraining moment with "overkill" in the mast ?
>
> However, this still wouldn't help the torque problem. If he's stuck with
> this tower and the given antenna family, how about a leg anchor plate and
> torque bars at the top of the tower ? This would also help the bending
> moment problem. Pretty soon a more heavy duty tower, or less ambitious
> antenna system, starts looking good !
>
> With some extra $$$ and a little engineering there will be a good answer.
>
> Gene / W2LU
>
> ----- Original Message -----
> From: <TexasRF at aol.com>
> To: <RShirbroun at newportlabs.com>; <towertalk at contesting.com>
> Sent: Wednesday, August 21, 2013 12:41 PM
> Subject: Re: [TowerTalk] Question on mast height above tower
>
>
>> Randy, a quick look at your proposed system shows that at 90mph, the
>> total
>> force applied to the top section is 666 foot pounds. 195 fp for the 40m
>> ant, 315 fp for the 6m beam and 150 fp for the Triband beam.
>>
>> If that force was from a single large antenna it would be the equivalent
>> of
>> 22 sq ft mounted one foot above the tower top.
>>
>> This is with NO safety factor and does not include loading for the 2" mast
>> or feedlines.
>>
>> This is more than the tower rating and you will have to decide if the risk
>> is acceptable. The bottom line is that the system would fail with a wind
>> speed somewhat less than 90mph, maybe 70mph or so.
>>
>> The mast proposed is an overkill. My computer program shows that a 2" OD
>> mast made with 1026 DOM, .125" wall will fail at 130 mph. This material is
>> available at Texas Tower of course!
>>
>> Hope this helps.
>>
>> 73,
>> Gerald K5GW
>> CEO Texas Towers
>>
>>
>> In a message dated 8/21/2013 8:25:38 A.M. Pacific Daylight Time,
>> RShirbroun at newportlabs.com writes:
>>
>> I didn't get any comments or suggestions to my previous post, so I'll try
>> again.
>> If this is a dumb question, feel free to tell me!
>>
>> I have just erected a new HDBX 40 in place of my 30 year old HBX 48,
>> sacrificing 8' of height to gain some strength and load capacity (and
>> peace of
>> mind!). The stock rotator plate allows 2' of mast below the top plate
>> and
>> I
>> will be using the heavy duty Yaesu thrust bearing (along with the Yaesu
>> heavy
>> duty 2800 rotator plus the absorber plate). I have added steel angle
>> braces
>> to reinforce the rotator plate.
>>
>> I'm looking at using a 15' chrome/steel 2" mast (in place of my previous
>> 9'
>> mast), so 13' of the mast would extend above the tower. The mast would
>> support
>> a TX38 tribander just above the top plate, a 6 m beam half-way up, and a
>> 40m
>> rotatable dipole near the top, 12' above the top tower plate and the
>> thrust
>> bearing. The mast, of course, is very heavy, weighing around 75lbs. The
>> tribander weighs 40lbs and with 5 ft2 surface area; the 6 m. beam weighs
>> 10lbs
>> with 1.5 ft2; the dipole weighs 10lbs and is 0.5 ft2.
>>
>> Is this too much mast for this tower? (BTW - I'm aware the boom length
>> exceeds the 10' maximum for this tower, but the HBX 48 handled a similar
>> tribander for 30 years, with occasional severe ice-loading, without any
>> problems.)
>>
>> Thanks and 73,
>> Randy, ND0C
>>
>>
>>
>> ________________________________
>> This e-mail and any files transmitted with it are confidential and
>> intended solely for the use of the individual or entity to whom they are
>> addressed. If you have received this e-mail in error please notify the
>> system
>> manager: postmaster at merial.com This e-mail and its attachments have been
>> scanned
>> for the presence of computer viruses, however it is always advisable to
>> run
>> a virus check on e-mails and attachments before opening them.
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
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>> _______________________________________________
>>
>>
>>
>> _______________________________________________
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>> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
> ------------------------------
>
> Message: 2
> Date: Wed, 21 Aug 2013 18:07:20 +0000
> From: Brian Alsop <alsopb at nc.rr.com>
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Question on mast height above tower
> Message-ID: <521501D8.3010603 at nc.rr.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Another possibility.
> Put the rotary 40m about 1' above the tribander and at right angles to it.
>
> The extra few feet of height lost won't amount to much. Also you would
> still have the advantage of pointing it at the signal of interest.
>
> That will help with the load, but won't impact the torque.
>
> 73 de Brian/K3KO
>
> On 8/21/2013 17:56, Gene Fuller wrote:
>>
>> These numbers looks like calc's for bending moment at the top of the tower.
>>
>> What about torque ?
>>
>> Would it be possible to put the rotor plate lower in the tower and pick
>> up some extra restraining moment with "overkill" in the mast ?
>>
>> However, this still wouldn't help the torque problem. If he's stuck
>> with this tower and the given antenna family, how about a leg anchor
>> plate and torque bars at the top of the tower ? This would also help
>> the bending moment problem. Pretty soon a more heavy duty tower, or less
>> ambitious antenna system, starts looking good !
>>
>> With some extra $$$ and a little engineering there will be a good answer.
>>
>> Gene / W2LU
>>
>> ----- Original Message ----- From: <TexasRF at aol.com>
>> To: <RShirbroun at newportlabs.com>; <towertalk at contesting.com>
>> Sent: Wednesday, August 21, 2013 12:41 PM
>> Subject: Re: [TowerTalk] Question on mast height above tower
>>
>>
>>> Randy, a quick look at your proposed system shows that at 90mph, the
>>> total
>>> force applied to the top section is 666 foot pounds. 195 fp for the 40m
>>> ant, 315 fp for the 6m beam and 150 fp for the Triband beam.
>>>
>>> If that force was from a single large antenna it would be the
>>> equivalent of
>>> 22 sq ft mounted one foot above the tower top.
>>>
>>> This is with NO safety factor and does not include loading for the 2"
>>> mast
>>> or feedlines.
>>>
>>> This is more than the tower rating and you will have to decide if the
>>> risk
>>> is acceptable. The bottom line is that the system would fail with a wind
>>> speed somewhat less than 90mph, maybe 70mph or so.
>>>
>>> The mast proposed is an overkill. My computer program shows that a 2" OD
>>> mast made with 1026 DOM, .125" wall will fail at 130 mph. This
>>> material is
>>> available at Texas Tower of course!
>>>
>>> Hope this helps.
>>>
>>> 73,
>>> Gerald K5GW
>>> CEO Texas Towers
>>>
>>>
>>> In a message dated 8/21/2013 8:25:38 A.M. Pacific Daylight Time,
>>> RShirbroun at newportlabs.com writes:
>>>
>>> I didn't get any comments or suggestions to my previous post, so I'll
>>> try
>>> again.
>>> If this is a dumb question, feel free to tell me!
>>>
>>> I have just erected a new HDBX 40 in place of my 30 year old HBX 48,
>>> sacrificing 8' of height to gain some strength and load capacity (and
>>> peace of
>>> mind!). The stock rotator plate allows 2' of mast below the top
>>> plate and
>>> I
>>> will be using the heavy duty Yaesu thrust bearing (along with the Yaesu
>>> heavy
>>> duty 2800 rotator plus the absorber plate). I have added steel angle
>>> braces
>>> to reinforce the rotator plate.
>>>
>>> I'm looking at using a 15' chrome/steel 2" mast (in place of my
>>> previous 9'
>>> mast), so 13' of the mast would extend above the tower. The mast would
>>> support
>>> a TX38 tribander just above the top plate, a 6 m beam half-way up, and a
>>> 40m
>>> rotatable dipole near the top, 12' above the top tower plate and the
>>> thrust
>>> bearing. The mast, of course, is very heavy, weighing around 75lbs.
>>> The
>>> tribander weighs 40lbs and with 5 ft2 surface area; the 6 m. beam weighs
>>> 10lbs
>>> with 1.5 ft2; the dipole weighs 10lbs and is 0.5 ft2.
>>>
>>> Is this too much mast for this tower? (BTW - I'm aware the boom length
>>> exceeds the 10' maximum for this tower, but the HBX 48 handled a similar
>>> tribander for 30 years, with occasional severe ice-loading, without any
>>> problems.)
>>>
>>> Thanks and 73,
>>> Randy, ND0C
>>>
>>>
>>>
>>> ________________________________
>>> This e-mail and any files transmitted with it are confidential and
>>> intended solely for the use of the individual or entity to whom they are
>>> addressed. If you have received this e-mail in error please notify
>>> the system
>>> manager: postmaster at merial.com This e-mail and its attachments have
>>> been scanned
>>> for the presence of computer viruses, however it is always advisable
>>> to run
>>> a virus check on e-mails and attachments before opening them.
>>> _______________________________________________
>>>
>>>
>>>
>>> _______________________________________________
>>> TowerTalk mailing list
>>> TowerTalk at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>
>>> _______________________________________________
>>>
>>>
>>>
>>> _______________________________________________
>>> TowerTalk mailing list
>>> TowerTalk at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>>
>> -----
>> No virus found in this message.
>> Checked by AVG - www.avg.com
>> Version: 2012.0.2242 / Virus Database: 3211/6095 - Release Date: 08/21/13
>
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2012.0.2242 / Virus Database: 3211/6095 - Release Date: 08/21/13
>
>
>
> ------------------------------
>
> Message: 3
> Date: Wed, 21 Aug 2013 16:37:12 -0400 (EDT)
> From: K7LXC at aol.com
> To: towertalk at contesting.com, RShirbroun at newportlabs.com
> Subject: Re: [TowerTalk] Rohn HDBX 40 - mast length
> Message-ID: <39e3a.422ef8f.3f467ef8 at aol.com>
> Content-Type: text/plain; charset="US-ASCII"
>
>> I have just erected a new HDBX 40 in place of my 30 year old HBX 48,
> sacrificing 8' of height to gain some strength and load capacity (and peace
> of mind!). The stock rotator plate allows 2' of mast below the top plate
> and I will be using the heavy duty Yaesu thrust bearing (along with the Yaesu
> heavy duty 2800 rotator plus the absorber plate). I have added steel
> angle braces to reinforce the rotator plate.
>
>> I'm looking at using a 15' chrome/steel 2" mast (in place of my
> previous 9' mast), so 13' of the mast would extend above the tower. The mast
> would support a TX38 tribander just above the top plate, a 6 m beam half-way
> up, and a 40m rotatable dipole near the top, 12' above the top tower plate
> and the thrust bearing. The mast, of course, is very heavy, weighing around
> 75lbs. The tribander weighs 40lbs and with 5 ft2 surface area; the 6 m.
> beam weighs 10lbs with 1.5 ft2; the dipole weighs 10lbs and is 0.5 ft2.
>
>> Is this too much mast for this tower? (BTW - I'm aware the boom
> length exceeds the 10' maximum for this tower, but the HBX 48 handled a similar
> tribander for 30 years, with occasional severe ice-loading, without any
> problems.)
>
> Well, I'd say you're pushing the limit. The capability of the tower
> vis-a-vis the proposed mast depends on 2 factors. First, the whole thing -
> including the top and rotator plates - are held together with aluminum
> rivets. They're easy to abuse and they won't take a lot of abuse.
>
> The second thing is that the plates are made from sheet metal. They
> don't have a lot of capacity to begin with. And with only 2 feet of mast in
> the tower, it's way top heavy and makes a nifty big lever arm.
>
> And BTW, Nobles County is an 85 MPH windspeed zone. Since Rohn rates
> the tower at 50 MPH, I'd say you've already exceeded the manufacturer's
> specs.
>
> So is this mast too much for this tower? I'd say so. It does have a
> high potential for failure so keep your homeowner's insurance paid up.
>
> Cheers,
> Steve K7LXC
> TOWER TECH -
> Professional tower services for amateurs
>
>
>
> ------------------------------
>
> Message: 4
> Date: Wed, 21 Aug 2013 17:19:24 -0400 (EDT)
> From: K7LXC at aol.com
> To: towertalk at contesting.com, k0gu at verinet.com
> Subject: Re: [TowerTalk] Rohn 45AG4 guy tabs?
> Message-ID: <32701.2ad4b035.3f4688dc at aol.com>
> Content-Type: text/plain; charset="US-ASCII"
>
>> I see at least one Rohn 45 seller's web site that calls the tabs on
> the 45AG4 top plate guy tabs. However I don't see any reference to that
> in the Rohn documentation. Except for dimensions Rohn doesn't really say
> a lot about the 45AG4. But Rohn always shows the guys attached a few
> feet below the tower. So are they guy tabs? I was planning on using them
> on a tower with a tall mast (the mast is another subject that will get a
> post here in a bit). Guy the tower at the top plate and then not far
> under the rotator. Anyone have the scoop on this.
>
> The 3 holes on the top plate of the 45AG4 are for guy attachments.
> This is more of a ham configuration. The reason that Rohn drawings show the
> guys installed a few feet below the top of the tower is for commercial
> applications where you might have fixed antennas mounted above and below the top
> of the tower and having the top guys a little lower allows for clearance of
> the headload. Commercial towers would tend to have a pointy-top top
> section than the more ham oriented flat topped one.
>
> BTW you'll need either big thimbles or more likely shackles (clevises)
> to join the terminated end of the guy with the holes in the top plate.
>
> Cheers & GL,
> Steve K7LXC
> TOWER TECH -
> Professional tower services for amateurs
> and
> Champion Radio Productw
>
>
>
> ------------------------------
>
> Message: 5
> Date: Wed, 21 Aug 2013 17:30:10 -0400 (EDT)
> From: K7LXC at aol.com
> To: towertalk at contesting.com, glhuber at msn.com
> Subject: Re: [TowerTalk] Penetrox/Noalox vs. Anti-seize compound
> Message-ID: <32abb.75ddc928.3f468b62 at aol.com>
> Content-Type: text/plain; charset="US-ASCII"
>
>> Well I'll be...I never thought there was anything else besides Penetrox
> and Noalox.
>
> In my UP THE TOWER book, there is a whole chapter on Corrosion and
> anti-oxidants. I list seven different anti-oxidant products.
>
> Cheers,
> Steve K7LXC
> Champion Radio Products
>
>
> ------------------------------
>
> Message: 6
> Date: Wed, 21 Aug 2013 17:48:15 -0400 (EDT)
> From: K7LXC at aol.com
> To: towertalk at contesting.com, n6sj at earthlink.net
> Subject: Re: [TowerTalk] Question on mast height above tower
> Message-ID: <330d3.6cde0fb4.3f468f9f at aol.com>
> Content-Type: text/plain; charset="US-ASCII"
>
>> If you can find a copy of Dave Leeson's "Physical Design of Yagi
> Antennas"
> (out of print) he explains how to calculate all the moments created by your
> combination of wind speed, boom/mast lengths and material types. Then you
> select the proper material, length and wall thickness to withstand those
> forces.
>
> We used Dave's book as a guide for our MARC Program (Mast, Antenna
> and Rotator Calculator). It's ten bucks at championradio.com.
>
>> That stack sounds like a big load on the base of the 2" mast, but
> whether it will hold depends on the yield strength of the chrome moly mast
> you use.
>
> IMO most of the people that buy expensive chromoly masts waste
> their money when there are other cheaper alternatives available; e.g. SAE
> 1026, DOM 520. There is a whole chapter on masts in my UP THE TOWER book.
>
> But in this scenario the mast is beside the point. I'd say the
> tower won't take the local windspeed conditions with the array that's being
> proposed.
>
> Cheers,
> Steve K7LXC
> TOWER TECH
>
> ------------------------------
>
> Message: 7
> Date: Wed, 21 Aug 2013 18:23:47 -0500
> From: rfman45 <rfman45 at hotmail.com>
> To: "towertalk at contesting.com" <towertalk at contesting.com>
> Subject: [TowerTalk] Different Type UHF Female
> Message-ID: <SNT148-W91049FF4BD79B49E9AFFBAB84C0 at phx.gbl>
> Content-Type: text/plain; charset="iso-8859-1"
>
>
> Today I came across what is stated to be a female UHF/SO-239 however there
> is no dielectric between the center and the shell, just the receptacle for
> the UHF male pin which is attached to the base. The outer shell
> is the usual threading and the UHF male fits it OK.
>
> My concern is its long term strength since it is unsupported until it finally
> reaches the base of the connector. I've never seen this type before.
> Has anyone had any experience with this type of UHF female?
>
> As always thanks in advance for any comments.
>
> Mike W2LO
>
>
> ------------------------------
>
> Message: 8
> Date: Thu, 22 Aug 2013 00:21:09 -0700
> From: Ray Benny <rayn6vr at cableone.net>
> To: TowerTalk <TowerTalk at contesting.com>
> Subject: [TowerTalk] Thoughts on Tower lifting cable broken strands
> Message-ID:
> <CAC716YZas=5bhw7WcfXrigAk05ToGF=Y6a+5jU6f-41V36xgaw at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> I'm in a dilemma.
>
> I purchase a used TM-490 90 ft Sky Needle and recently found some of the
> 5/16", 7 X 19 aircraft cable lifting cable strands broken. The tower is on
> the ground and not been in the vertical position for a number of years. The
> problem, apparently there was some gas torch cutting done nearby and
> splatter landed on the cable. This molten metal landed on the pull up cable
> causing it to burn and sever 2 - 3 strands in one area, and another 3 - 4
> strands 6 inches higher up the cable. The cable overall is otherwise in
> very good condx with no wear marks. It might have been replaced prior and
> the tower has been laying on the ground ever since?
>
> The best and right thing to do is to replace the cable. But, I have been
> going through my options:
>
> #1 - Do the cable replacing myself. I have found the cable and cable
> pulling grip for less that $200. The major problem is that this is a 3200
> lbs tabular tower and not easy to move around. I would need to rent small
> boom truck or forklift and some other misc working hardware to pull the
> sections apart. It would not be easy, but feel I could do the job.
>
> #2 - Hire someone to come here and do the job. This can run into a 4 - 5
> thousand dollar cost.
>
> #3 - Transport the tower to California and have it restring by the tower
> company who made it long ago. I've checked commercial transport rates, r/t
> shipment and cable replacement cost is more than option #2.
>
> #4 - Do nothing and live with a few broken strands.
>
> *At this point I am looking for thoughts, experiences and/or
> semi-professional thoughts on option #4 - do nothing*. I've had a one
> experienced tower person say that 6 - 8 broken strands out of 133 is
> nothing.
>
> Again, I know the proper/safe thing to do is replace the cable, but how
> about doing nothing and using the tower as is?
>
> Tnx,
>
> Ray,
> N6VR
>
>
> ------------------------------
>
> Subject: Digest Footer
>
> _______________________________________________
> TowerTalk mailing list
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>
>
> ------------------------------
>
> End of TowerTalk Digest, Vol 128, Issue 80
> ******************************************
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