[TowerTalk] [Bulk] Re: Phillystran
Roger (K8RI) on TT
K8RI-on-TowerTalk at tm.net
Thu Oct 22 23:10:44 EDT 2015
I have the docs that came with the 4000 and 6000# test lines and they do
not mention the Spelter sockets. They do say to use Big Grips and not
saddle clamps. For Amateur use it's probably an abbreviated sheet.
they only go to the 6000# cables. With a 100' 45G, I use the 6000# test
for the top tier and the 4000# test for the bottom two.
I was aware of the socket requirement for the older Phillystran. I did
not see the older cables referenced in your post, nor do I see any
links. Just a reference to the NCJ which I do not have. Hams purchasing
the 4000 and 6000# test Phillystran will likely see no reference to
Spelter sockets.
I would not use saddle clamps on the 4000, or 6000# test lines because
of the very thick jackets over a relatively small Kevlar core. The
larger sizes above the 6000# test likely have even more jacket In those
instances you are pretty much clamping the jacket and not the core.
I think you will find little creep with the 3 saddle clamps on the 1200#
test cable used well within its ratings as the jacket is much thinner
compared to the larger cables and under no where near as much stress.
With 3 clamps spaced 3" there is no need to tighten the clamps to the
point of destroying the jacket.
The 1200# test makes a good truss material except for very large
antennas, or a shallow truss where the center is relatively close to
the boom. I've had no problems using the 1200# test well within its
ratings. I wish I had replaced the Al tube truss on the 7L C3i 6-meter
Yagi with the 1200# Phillystran when I first put it up. True, it's not
a huge monobander, but at a couple inches shy of 30 feet it does need a
truss. A flock of Cormorants using the antenna as an over night roost
broke the tube truss.
There was mention of pretensioning of the truss. That would not be
possible on most antennas, however once the cables are cut to length and
properly terminated, they can be pretensioned in an external fixture,
but as the tension in use will likely be less than the usual 10%
operating tension I doubt there would be any need to do so.
73
Roger (K8RI)
On 10/22/2015 9:42 AM, Grant Saviers wrote:
> Roger,
>
> I think you should read the Phillystran docs a bit more carefully, see
> my prior post for links. Philly is still terminated with a Spelter
> like socket. Big Grips are available on the lower strength guys
> (except 1200).
>
> From the specs: "The Corona Sockets are aluminum, resin filled,
> potted end terminations and are always factory installed." Available
> at the 1200 size and larger, although not for every break strength cable.
>
> If you read my NCJ article, it is about older Philly that must be
> terminated with epoxy filled sockets, Big Grips do not work on any
> size. However, according to my discussion with Phillystran
> engineering, they do not sell the sockets any more except to the
> military and perhaps special contractors. Also, the factory epoxy is
> not available in the USA even though it is in catalogs. With about
> 1500' of 25k old Philly on hand, I was in search of a full strength
> and reliable termination technique and proved it with extensive long
> term tension testing and testing to failure.
>
> They changed to Big Grips on the smaller sizes when they changed the
> core design from parallel strand Kevlar fibers to that similar to
> conventional 3 strand stranded rope, although there are more strands
> of Kevlar in current Philly.
>
> Anecdotes, "my boom hasn't bent yet" are interesting, but show me the
> tension test data for saddle clamp terminations that were installed a
> few months ago.
>
> I still have my tension tester, able to generate 20k lbs tension and
> someday might get around to some more tests.
>
> Grant KZ1W
>
> On 10/22/2015 0:26 AM, Roger (K8RI) on TT wrote:
>> This should not be a factor where the Phillystran is used as a truss
>> at a fraction of its strength. As guy lines the standard "Big Grip is
>> recommended. They haven't used Spelter sockets and epoxy for some
>> years even on the larger 6,000# cable.
>>
>> For a truss 3 saddle clamps are used with the saddle on the live side
>> (never saddle a dead horse) so creep has never been a problem when
>> used on a truss. The Big Grips (Recommended by Phillystran and sold
>> by vendors) grip entirely on the jacket, but it's over about 18" or
>> more. If you wrote a recent article recommending Spelter sockets, it
>> is not what the manufacturer recommends, hence they have not been the
>> proper method of termination for a number of years. I don't know
>> when they changed, but it was Big Grips in 2002, or 13 years ago when
>> I installed my 45G using Phillystran's recommendations. I didn't
>> find any sellers of Phillystran even offering Spelter sockets.
>>
>> Follow the "Prime Directive"
>>
>> 73
>>
>> Roger (K8RI)
>>
>>
>> On 10/21/2015 11:35 PM, Grant Saviers wrote:
>>> I strongly advise against saddle clamps. The problem is creep of the
>>> plastic jacket causes the clamp force to decay with time. Until the
>>> clamp completely cuts through the jacket the clamp force decays. At
>>> room temperature it took about 3 weeks and at least 4 tightenings to
>>> get the saddle to cut through the jacket. I used a torque wrench to
>>> set the tightening force and measured the residual torque at a late
>>> time each cycle. I built a tension tester and verified saddle
>>> terminations will slip well below the breaking strength of the
>>> Philly. Even after 121 days and 4 tightening cycles the saddle
>>> clamp torque values indicated continuing creep and reduced
>>> termination strength. I was unable to achieve more than 30% of the
>>> break strength of the Philly. (25000# Philly and 7000# load for
>>> slippage).
>>>
>>> Later I tested the proper terminations for this Philly (Spelter
>>> sockets with epoxy) on a commercial 100,000# tension test stand and
>>> the guy failed at 28000# tension and not the termination. See NCJ
>>> Nov-Dec 2014 for my article.
>>>
>>> I've seen bent booms as a result of using saddle clamps. I also
>>> found them loose on my steppIR 4L after a year on the 1200 size so
>>> will never use it again.
>>>
>>> Phillystran says use grips on all 2100 and larger. Follow the
>>> directions!
>>>
>>> Grant KZ1W
>>>
>>> On 10/21/2015 13:06 PM, Mike Reublin NF4L wrote:
>>>> Mostly what compresses is the jacket. No strength is lost. My
>>>> SteppIR uses Phillystran (as a bridle) with small saddle clamps.
>>>> The PS is very flat in the clamps.
>>>> 73, Mike NF4L
>>>>
>>>>
>>>>> On Oct 21, 2015, at 3:46 PM, GMuller885--- via TowerTalk
>>>>> <towertalk at contesting.com> wrote:
>>>>>
>>>>> All:
>>>>> Thank all of you for the input. Based on all the input my
>>>>> guys and
>>>>> stays are of Phillystran 6mm dia 2100 lbs break strength. I am
>>>>> using guy
>>>>> line clamp kits, three to a connection. The only question left
>>>>> is that if
>>>>> the Guy cliompress the Phillystran how much strength is lost if any?
>>>>>
>>>>> Gerald Muller K9GEM
>>>>> GMuller885 at aol.com
>>>>> _______________________________________________
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> TowerTalk mailing list
>>>>> TowerTalk at contesting.com
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>>>>
>>>>
>>>>
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>>>
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>>
>
--
73
Roger (K8RI)
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