[TowerTalk] Forced required on guys
Drax Felton
draxfelton at gmail.com
Fri Dec 2 08:35:44 PST 2011
One might string some protective cables to deflect the falling branches? Possible?
Sent from my iPhone
On Dec 2, 2011, at 10:11 AM, towertalk-request at contesting.com wrote:
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> Today's Topics:
>
> 1. cushcraft D3W (Bill Feissner)
> 2. Force required on guys to cause catastrophic failure? Have
> your guys been struck by falling limbs? (John W)
> 3. Re: Which type of cable for a crank-up tower?
> (krishna kanakasapapathi)
> 4. Re: TowerTalk Digest, Vol 108, Issue 6 (Craig Clark)
> 5. Cost effective Tower height (Jim Thomson)
> 6. Re: Cost effective Tower height (K1TTT)
> 7. Re: cushcraft D3W (Bert Almemo)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 1 Dec 2011 15:10:22 -0500
> From: "Bill Feissner" <ai3q at pa.metrocast.net>
> Subject: [TowerTalk] cushcraft D3W
> To: <towertalk at contesting.com>
> Message-ID: <460D33EA25AF4B79BA8CBCC2AA7A0DCE at BILL>
> Content-Type: text/plain; charset="iso-8859-1"
>
> What kind of opinion s there about mounting a D3W 5 feet under a 402cd. The 402cd is about 5 feet above the top of the tower and can't go any higher. I can mount the D3W paralell to the elements or run it with the boom. I know a yagi would be better but I am out of tower space except for this area. I did at one time have a 40 rotatible dipole under a 5 el tribander running with the boom about 7 feet below it with no ill effects...any thoughts on this. thanks
> Bill, AI3Q
>
> ------------------------------
>
> Message: 2
> Date: Fri, 2 Dec 2011 04:29:20 -0800
> From: John W <xnewyorka at hotmail.com>
> Subject: [TowerTalk] Force required on guys to cause catastrophic
> failure? Have your guys been struck by falling limbs?
> To: <towertalk at contesting.com>
> Message-ID: <BAY163-W245EDC4253ADBDD35BF532A5B60 at phx.gbl>
> Content-Type: text/plain; charset="iso-8859-1"
>
>
> This is a two-part question. There is a small survey at the end for those who have had a guy struck by a falling limb or tree.
>
> My main question is: Are there any engineers out there who can tell me how to calculate the downward force on a guy that would cause a breakage or catastrophic failure?
>
> The reason I ask is that regardless of where I place my to-be-built tower, I cannot avoid having guys passing through the woods, and I am in a high wind area.
> There are constantly limbs, and sometimes even trees of various sizes, getting knocked down by the wind.
>
> I realize that if a huge tree falls on a set of guys, it's probably all over. That's a risk I'll have to take, and I plan to monitor tree health closely.
> What I am more concerned about is the large number of limbs, some of which are fairly sizable, that fall when the wind blows.
>
> I can measure the weight of a typical limb. They are mostly 2 lbs. to 5 lbs. But let's say I want to plan for the occasional big one, say 75 lbs.
> If it falls from a height of 80' before hitting a guy, I can calculate the acceleration due to gravity and calculate the force it has using F=MA.
> (I will have to break out the college physics book to do this, but I should be able to do it!)
>
> Now that I know the force, I can compare that figure against the force needed to either a) snap the guy wire it hits, or b) put so much instantaneous tension on the guy that it causes the tower to buckle.
> (Sorry to cause the inevitable cringing here, but...) I assume the tower would probably buckle at the point of attachment of the guy below the guy that got struck.
> It's also a reasonable assumption that it is most likely to be the top guy that gets struck. Although it's also entirely possible that a tree off to the side falls down, and the top of the tree strikes a lower guy in the latter part of its trip to the ground.
> In that case, the force on the guy would have both a downward and a lateral component. It would also be a lot harder for me to remember how to calculate the striking force in that case.
>
> I assume that some of the other factors needed in order to make a correct calculation would be the tower type (Rohn 25G, 45G, or 55G), the guy material (which would be per factory spec), and the distance between the struck guy and the one above it or below it.
>
> I realize it's asking a lot for someone to provide the formula(s) needed to make this calculation, but if there is anybody out there who would know, I figured this would be the best place to find them! (Or is this something I can ask the tower manufacturer?)
>
> On a practical level, I'm sure there must be some of you who have had limbs fall on guys. I'm interested to hear:
>
> What size/weight of limb hit the guy?
> What was the tower configuration (height, type, and guy material)?
> Which guy got struck?
> How far did the limb fall?
> What was the result? Damage or no damage?
>
> Thanks for all input,
>
> John
> W2ID
>
> ------------------------------
>
> Message: 3
> Date: Fri, 02 Dec 2011 07:43:07 -0500
> From: krishna kanakasapapathi <kkanakas at cisco.com>
> Subject: Re: [TowerTalk] Which type of cable for a crank-up tower?
> To: John Lemay <john at carltonhouse.eclipse.co.uk>
> Cc: towertalk at contesting.com
> Message-ID: <4ED8C7DB.1070709 at cisco.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> John et all,
> I just recabled my tower the past week. I found that the 5 year old
> (perhaps older) stainless steel cable
> showed signs of slight rust on the coiled up rounds on the drum of the
> winch.
> I was hoping that the prelube will prevent the corrosion on that part
> of the cable. I don't know if the polymer coat will stay intact on the
> exposed run of the cables.
>
> krish
> w4vku
>
> On 12/2/2011 4:34 AM, John Lemay wrote:
>> If you oil the cable, won't the oil wash off the first time it rains ?
>>
>> John G4ZTR
>>
>> -----Original Message-----
>> From: towertalk-bounces at contesting.com
>> [mailto:towertalk-bounces at contesting.com] On Behalf Of krishna
>> kanakasapapathi
>> Sent: 01 December 2011 22:24
>> To: towertalk at contesting.com
>> Subject: Re: [TowerTalk] Which type of cable for a crank-up tower?
>>
>> For my Aluma tower, the company recommended the 7x19 stainless steel cable.
>> I have ordered the penetrating oil from champion radio to protect the cable.
>> Regardless, i plan to replace the cables every 3 or 4 years depending on
>> the condition.
>>
>> For a salty air environment, wouldn't stainless steel be better?
>> 73s
>> krish
>> w4vku
>>
>> On 12/1/2011 5:00 PM, Dan Levin wrote:
>>> Of course, if I knew who made it I would just get the manual and do what
>> they say. But I don't know who made it, so...
>>> I have an unidentified 65' crank-up tower, believed to be of English
>> origin. It needs to be recabled. The existing (original) cable appears to
>> be 5/16", but it might be 8mm or even 7mm (I am not where the tower is, so I
>> can't measure it exactly). Definitely bigger than 1/4". The tower lives in
>> a very salty, island climate.
>>> I am trying to figure out what type of cable to use - not which size, but
>> which material and construction.
>>> The easiest thing to find that seems appropriate is 5/16" 7x19 galvanized
>> steel.
>>> But, I have read that these towers usually use 6x19 LC (linen core) -
>> which I can find in plain steel, but not in galvanized.
>>> 1) Is galvanized the way to go in this situation?
>>>
>>> 2) Any sense of which construction is most appropriate? I assume 7x19
>> would be best if I can't find the 6x19 LC.
>>> 3) Anyone have a source of 6x19 LC galvanized 5/16" cable?
>>>
>>> ***dan, K6IF
>>> _______________________________________________
>>>
>>>
>>>
>>> _______________________________________________
>>> TowerTalk mailing list
>>> TowerTalk at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>
>> _______________________________________________
>>
>>
>>
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>
>
>
> ------------------------------
>
> Message: 4
> Date: Fri, 2 Dec 2011 08:59:04 -0500
> From: "Craig Clark" <jcclark at myfairpoint.net>
> Subject: Re: [TowerTalk] TowerTalk Digest, Vol 108, Issue 6
> To: <towertalk at contesting.com>
> Message-ID: <09c901ccb0fa$8e3c2280$aab46780$@net>
> Content-Type: text/plain; charset="us-ascii"
>
> Can we please edit responses. Delete is getting worn off my keyboard.
>
> There is no need to include everything when you respond.
>
> Thanks
>
> Craig
>
>
>
>
>
> ------------------------------
>
> Message: 5
> Date: Fri, 2 Dec 2011 06:12:25 -0800
> From: "Jim Thomson" <jim.thom at telus.net>
> Subject: [TowerTalk] Cost effective Tower height
> To: <towertalk at contesting.com>
> Message-ID: <CC87354A095E44198C9F5017DD5F0040 at JimboPC>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Date: Thu, 01 Dec 2011 19:16:14 +0000
> From: Steve Hunt <steve at karinya.net>
> Subject: Re: [TowerTalk] Cost effectivel Tower height
>
> I think we sometimes concentrate too much on looking at antenna heights
> that will maximize gain at certain take-off angles, and forget about the
> nulls. Those deep elevation nulls can be "killers" if arrival angles
> over a wanted path happen to fall in them.
>
> So, before going firm on a height I'd encourage you to look at the ARRL
> Angle-of-Arrival statistics for various bands and paths, and make sure
> your selected height is not going to put a deep null at a high
> probability arrival angle for the bands/paths you are most interested
> in. It might be a better trade to be 1dB weak for 80% of the time rather
> than 20dB weak for 20% of the time, if you get my point.
>
> 73,
> Steve G3TXQ
>
> ## I'd agree on this. For a single height, I'd opt for 70-85' range.
> 70' is a winner every time for a single height, for a multiband 40-10m
> yagi that you propose. Back in the late 1970's here in town, we had one
> fellow with his tribander at 50'..... and another fellow with 20 m monobander
> at 100'...[ and with a 10/15 m interlaced array, 10' above the 20m yagi].
>
> ## The fellow with the 100' tall yagi would win out 85% of the time for dx to eu,
> but not asia, or south pacific. A lot of times the station with the 50' high tribander
> would clean the other fellow's clock. That happened quite often. I came along, with
> my 20m yagi at 72'..and the 15m yagi 8' higher. 95% of the time I was as loud as the
> 100' tall yagi....and at no time did the 50' tall tribander beat me out. I trounced the
> 50' tall array, hands down, any direction, any time of the day.
>
> ## after 2 years of this back and forth testing, my conclusion was most of the time, the
> angles were aprx 15 deg.... and that 10 degs was too low...and 20 deg was too high.
> To make matter's worse.... the fellow with the 100' high ant [10 deg angle] had a perfect
> NULL at 20 degs ! And of course the fellow with the 50' high tribander had max gain at
> 20 degs.
>
> ## Higher is better..up to a point, then you get too high, and then u have diminishing returns, PLUS
> you now have a big null at 20 degs. Of course if you have a motorized crank up, you can have
> your cake and eat it too. Since your proposed array is a 40-10m affair, I'd suggest 80'.
> A T-400 trylon would fit the bill, [ or the AN wireless 80', which is a lot stronger tower].
> Don't go cheap on the rotor, it's a one shot deal, PST-61, OR-2800, something big, with loads
> of TQ. Use anything smaller, and you will trash it, then you will have to replace with a big rotor
> anyway, so you saved...nothing.
>
> ## OK, you have neg 5 deg slope in all directions. I'd opt for 70' then. Like a T-500 trylon,
> or the 70' an wireless. Don't go cheap on the tower either..u want the WIDE base. If using the
> trylon, make it 6' deep, instead of 5 1/2'..and use a grid of re-bar across the top, so u have re-bar on
> 5 x sides..and use 30 mpa concrete [ 4350 psi..or at least 4000 psi]. The tower and the base is
> another one shot deal. In a 70+ mph wind + ice, then you can sleep at night. Freestanding tower's
> are a lot easier to deal with when installing any yagi..and no guys to mess with. By the time you
> buy the megabuck phillystran and the rohn 45, guy brackets, turnbuckles, loos gauge, etc,
> then install 3 x concrete guy anchor's, you will have saved nothing...or very little.
>
> later... Jim VE7RF
>
>
>
> ------------------------------
>
> Message: 6
> Date: Fri, 02 Dec 2011 14:59:17 +0000
> From: "K1TTT" <K1TTT at ARRL.NET>
> Subject: Re: [TowerTalk] Cost effective Tower height
> To: <towertalk at contesting.com>
> Message-ID: <003f01ccb102$f814b7a0$e83e26e0$@ARRL.NET>
> Content-Type: text/plain; charset=US-ASCII
>
> That's what stacks are for!
>
> David Robbins K1TTT
> e-mail: mailto:k1ttt at arrl.net
> web: http://wiki.k1ttt.net
> AR-Cluster node: 145.69MHz or telnet://k1ttt.net
>
> -----Original Message-----
> From: Jim Thomson [mailto:jim.thom at telus.net]
> Sent: Friday, December 02, 2011 14:12
> To: towertalk at contesting.com
> Subject: [TowerTalk] Cost effective Tower height
>
> Date: Thu, 01 Dec 2011 19:16:14 +0000
> From: Steve Hunt <steve at karinya.net>
> Subject: Re: [TowerTalk] Cost effectivel Tower height
>
> I think we sometimes concentrate too much on looking at antenna heights that
> will maximize gain at certain take-off angles, and forget about the nulls.
> Those deep elevation nulls can be "killers" if arrival angles over a wanted
> path happen to fall in them.
>
> So, before going firm on a height I'd encourage you to look at the ARRL
> Angle-of-Arrival statistics for various bands and paths, and make sure your
> selected height is not going to put a deep null at a high probability
> arrival angle for the bands/paths you are most interested in. It might be a
> better trade to be 1dB weak for 80% of the time rather than 20dB weak for
> 20% of the time, if you get my point.
>
> 73,
> Steve G3TXQ
>
> ## I'd agree on this. For a single height, I'd opt for 70-85' range.
> 70' is a winner every time for a single height, for a multiband 40-10m yagi
> that you propose. Back in the late 1970's here in town, we had one fellow
> with his tribander at 50'..... and another fellow with 20 m monobander at
> 100'...[ and with a 10/15 m interlaced array, 10' above the 20m yagi].
>
> ## The fellow with the 100' tall yagi would win out 85% of the time for dx
> to eu,
> but not asia, or south pacific. A lot of times the station with the 50'
> high tribander
> would clean the other fellow's clock. That happened quite often. I came
> along, with
> my 20m yagi at 72'..and the 15m yagi 8' higher. 95% of the time I was as
> loud as the 100' tall yagi....and at no time did the 50' tall tribander
> beat me out. I trounced the
> 50' tall array, hands down, any direction, any time of the day.
>
> ## after 2 years of this back and forth testing, my conclusion was most of
> the time, the angles were aprx 15 deg.... and that 10 degs was too
> low...and 20 deg was too high.
> To make matter's worse.... the fellow with the 100' high ant [10 deg
> angle] had a perfect
> NULL at 20 degs ! And of course the fellow with the 50' high
> tribander had max gain at
> 20 degs.
>
> ## Higher is better..up to a point, then you get too high, and then u have
> diminishing returns, PLUS you now have a big null at 20 degs. Of course if
> you have a motorized crank up, you can have
> your cake and eat it too. Since your proposed array is a 40-10m affair,
> I'd suggest 80'.
> A T-400 trylon would fit the bill, [ or the AN wireless 80', which is a
> lot stronger tower].
> Don't go cheap on the rotor, it's a one shot deal, PST-61, OR-2800,
> something big, with loads of TQ. Use anything smaller, and you will trash
> it, then you will have to replace with a big rotor anyway, so you
> saved...nothing.
>
> ## OK, you have neg 5 deg slope in all directions. I'd opt for 70' then.
> Like a T-500 trylon, or the 70' an wireless. Don't go cheap on the tower
> either..u want the WIDE base. If using the trylon, make it 6' deep, instead
> of 5 1/2'..and use a grid of re-bar across the top, so u have re-bar on
> 5 x sides..and use 30 mpa concrete [ 4350 psi..or at least 4000 psi]. The
> tower and the base is
> another one shot deal. In a 70+ mph wind + ice, then you can sleep at night.
> Freestanding tower's are a lot easier to deal with when installing any
> yagi..and no guys to mess with. By the time you buy the megabuck
> phillystran and the rohn 45, guy brackets, turnbuckles, loos gauge, etc,
> then install 3 x concrete guy anchor's, you will have saved nothing...or
> very little.
>
> later... Jim VE7RF
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
> ------------------------------
>
> Message: 7
> Date: Fri, 2 Dec 2011 10:11:01 -0500
> From: Bert Almemo <balmemo at sympatico.ca>
> Subject: Re: [TowerTalk] cushcraft D3W
> To: "'Bill Feissner'" <ai3q at pa.metrocast.net>,
> <towertalk at contesting.com>
> Message-ID: <BLU0-SMTP77F6D429B52CC50B645D99D4B60 at phx.gbl>
> Content-Type: text/plain; charset="us-ascii"
>
> Hi Bill,
>
> This topic has been discussed before and the simple answer is that you can
> mount the dipole on the same boom as the 402CD if you want. There will be
> very little or no interaction.
>
> A friend of mine put a D3W on a 10/15/20M yagi between the driven element
> and the reflector. He's had it for years and it works great. Good luck!
>
> 73 Bert, VE3NR
>
>
>
> -----Original Message-----
> From: towertalk-bounces at contesting.com
> [mailto:towertalk-bounces at contesting.com] On Behalf Of Bill Feissner
> Sent: Thursday, December 01, 2011 3:10 PM
> To: towertalk at contesting.com
> Subject: [TowerTalk] cushcraft D3W
>
> What kind of opinion s there about mounting a D3W 5 feet under a 402cd. The
> 402cd is about 5 feet above the top of the tower and can't go any higher. I
> can mount the D3W paralell to the elements or run it with the boom. I know a
> yagi would be better but I am out of tower space except for this area. I did
> at one time have a 40 rotatible dipole under a 5 el tribander running with
> the boom about 7 feet below it with no ill effects...any thoughts on this.
> thanks Bill, AI3Q _______________________________________________
>
>
>
> _______________________________________________
> 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
>
>
> End of TowerTalk Digest, Vol 108, Issue 7
> *****************************************
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