Gerald provided excellent insight into the apparent disparity between the
guidance in Preformed Line Products (PLP) application notes (which specify 1/2
inch heavy duty (HD) thimbles for use with 1/4 inch guy wire) vs. Rohn's
drawings (which specify 3/8 inch HD thimbles for the same guy wire).
Reviewing the PLP application notes in further detail, they specify the
following minimum seat diameters for some commonly used Big Grips:
Big Grip Size Minimum Seat Diameter
1/4 inch 1 1/8 inch
5/16 1 1/4
3/8 1 3/8
The seat diameter for some commonly used HD thimbles is:
HD Thimble Size HD Seat Diameter
3/8 inch 1 1/8 inch
7/16 1 1/4
1/2 1 1/2
Thanks Gerald!
73
Frank
W3LPL
---- Original message ----
>Date: Sat, 2 Sep 2006 10:50:21 EDT
>From: TexasRF@aol.com
>Subject: Re: [TowerTalk] Rohn 55 thimbles and turnbuckles
>To: towertalk@contesting.com
>
>
>Hi All, here is a bit of clarification on the Big Grip and thimble size
>issues:
>
>Rohn does not make Big Grips; Preformed Line Products Co. makes them and
>sells them to Rohn. 1/4" EHS uses a BG2144. All BG2144 grips are the same
>design
>whether purchased through Rohn/Radian or other distributors, such as Texas
>Towers. There are other grips made for utility use that fit 1/4" EHS but they
>are shorter, have fewer strands and not recommended for tower guy
>applications. These other grips will not be identified as Big Grips.
>
>For the 1/4" Big Grip, BG2144, Preformed Products calls for a 1/2" thimble
>and Rohn/Radian calls for a 3/8" heavy thimble. The groove in these two sizes
>have the same dimension so it makes sense that either a 1/2" regular thimble
>or a 3/8" heavy thimble will work fine. Texas Towers carries the heavy series
>
>because this is the size recommended by Rohn/Radian.
>
>A 3/8" heavy thimble is a very close fit into the eye of a 1/2" X 12
>turnbuckle. Once the legs are twisted apart, it takes only a slight
>"persuasion" to
>push the thimble through the eye of the turnbuckle. If this seems like too
>much effort then by all means a 1/2" shackle can be used to connect the
>thimble
>and turnbuckle. Texas Towers has these shackles in stock as they are required
> when connecting Phillystran grips/thimbles to turnbuckles and other
>hardware.
>
>Joining Phillystran to EHS can be done by back to back thimbles or with
>shackles.
>
>73,
>Gerald Williamson
>General Manager/Texas Towers
>
>
>
>
>
>
>In a message dated 8/31/2006 6:22:47 A.M. Central Daylight Time,
>donovanf@starpower.net writes:
>
>Hi Dick,
>
>It seems unlikely that Rohn makes preformed Big Grips.
>Preformed specifies use 1/2 inch heavy duty thimbles. The cost isn't much
>higher than 3/8 inch heavy duty thimbles. The only way to resolve this is to
>communicate directly with engineers at the companies involved...
>
>You would probably regret fastening Big Grips (and thimbles...) to the guy
>attachments without use of shackles. As you point out, it would be
>inconvenient to remove the guys.
>
>3/8 inch shackles are an ideal match to the load capacity of 1/4 inch EHS
>guy wire (5/16 inch shackles have a breaking load capacity of 6600 pounds,
>slightly less than the breaking load capacity 1/4 inch EHS). In my previous
>e-mail I recommended that you use 7/16 inch shackles; however, their 13,300
>pound breaking load capacity in unnecessarily large for your guy system.
>
>Good luck with your new tower installation Dick!
>
>73!
>Frank
>W3LPL
>
>---- Original message ----
>>Date: Thu, 31 Aug 2006 03:19:45 -0400
>>From: "Dick Green WC1M" <wc1m@msn.com>
>>Subject: Re: [TowerTalk] Rohn 55 thimbles and turnbuckles
>>To: <donovanf@starpower.net>, <towertalk@contesting.com>
>>
>>Frank,
>>
>>Glad you weighed in on this.
>>
>>I got 1/2" thimbles for the Preformed Grips I'm using with the 6700 lb
>>Phillystran -- as specified on the Texas Towers website. So far, so good.
>>
>>But I ordered 3/8" heavy-duty thimbles for the 1/4" EHS bottom leaders
>>because that's what Rohn specifies for use with their 1/4" EHS Big Grips
>>(part # BG2144.) Here's a link to the parts list in the Rohn catalog:
>>
>>http://www.antennasystems.com/PDFs/ROHN/55G/55G-14.pdf
>>
>>I'm using 6700 lb Phillystran with 1/4" EHS leaders on all three guys,
>which
>>isn't quite up to the 110 MPH spec (the top guy is supposed to be 5/16"),
>>but exceeds the 90 MPH spec. The parts list shows BG2144 grips and 3/8"
>>thimbles for the 1/4" EHS. Is there a difference between Rohn Big Grips and
>>Preformed Big Grips?
>>
>>Do you think the Rohn-specified 3/8" thimbles are OK for their 1/4" EHS
>>grips? If so, would you still use a 7/16" shackle, or something smaller?
>>What's a good source for high-quality shackles? Would you recommend using
>>shackles to connect the 1/2" thimbles at the end of the Phillistran grips to
>>the solid links on the GA55GD guy brackets? Here's a diagram of the
>bracket:
>>
>>http://www.antennasystems.com/PDFs/ROHN/hardware_accessories/HA-79.pdf
>>
>>The 1/2" thimble should fit inside the loop OK, but a shackle would make
>>installation and removal easier.
>>
>>73, Dick WC1M
>>
>>-----Original Message-----
>>From: donovanf@starpower.net [mailto:donovanf@starpower.net]
>>Sent: Wednesday, August 30, 2006 9:00 PM
>>To: towertalk@contesting.com
>>Subject: Re: [TowerTalk] Rohn 55 thimbles and turnbuckles
>>
>>Dick,
>>
>>1/2" heavy duty thimbles are required by Preformed Line Products for use
>>with their Big Grips for 1/4" guy wire and Phillystran.
>>
>>See:
>>http://www.preformed.com/artsfest/files/AppProc/SP2049-3.pdf
>>http://www.preformed.com/artsfest/files/AppProc/SP2806.pdf
>>
>>Use a 7/16" shackle to make the transition from the thimble to the
>>turnbuckle.
>>
>>73!
>>Frank
>>W3LPL
>>
>>---- Original message ----
>>>Date: Wed, 30 Aug 2006 19:47:29 -0400
>>>From: "Dick Green WC1M" <wc1m@msn.com>
>>>Subject: [TowerTalk] Rohn 55 thimbles and turnbuckles
>>>To: "Tower" <towertalk@contesting.com>
>>>
>>>Reviewing the Rohn parts list for a 110â 55G tower @90-100MPH, I
>>>decided to go with Ââ EHS for all three levels (actually, 6700lb
>>Phillystran with Ââ
>>>EHS leaders. Following the parts list, I ordered 3/8â heavy-duty
>>>thimbles
>>>(3/8THH) and Ââx12â eye-jaw turnbuckles (1/2TBE&J). Rohn specifies
>>>that
>>>the thimble should be one size larger than the guy diameter. The parts
>>>have arrived, and Iâm perplexed to find that the 3/8â thimbles donât
>>>fit inside the eye part of the turnbuckles. I might be able to make
>>>them fit by flattening the edges of the thimble a bit (sandwiching it
>>>between a piece of two pieces of flat steel and hammering the flare out
>>>of the edges), but before I try that, Iâd like opinions on this. I
>>>canât be the first person who has run into this. It looks like a
>>>shackle would work, but Rohn doesnât specify them for 55G towers.
>>>Comments?
>>>
>>>
>>>
>>>73, Dick WC1M
>>>
>>>
>>>
>>>_______________________________________________
>>>
>>>
>>>
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>>>http://lists.contesting.com/mailman/listinfo/towertalk
>>
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