Stringing Open Wire 101

Stringing Open Wire Basic 101

This is an exciting chapter of the Song website.  The physical act of building an open wire toll or exchange line is lost if the stringing of conductors is not part of the story.  The stringing of wire involves some danger and lots of physical strength. 

 

It is the future of this website to feature a video, not only describing design, drafting and construction of an actual open wire toll lead to AT&T specs, but to actually view the various construction stages from beginning to end.  We will initiate the project with preliminary design and subsequent drafting structure details, followed by the dual events of easement/right-of-way authorization to staking the line route, which will continue the drama.  Finally, poles will be set, guys and anchors installed, arms placed, and stringing process will begin.  Our example will feature terminal structures, H-fixtures, alley-arm types, double arm 45-degree corner poles, transposed, along with various protections, terminals, SAI enclosures (with balcony), drops and other important aspects of 1920s linework. 

 

Meanwhile, for those of you at home, hungering to build your own line–in model form–or for real, I will offer you now the following instruction.  But first get out the tools so we can realize the task before us with safety and ease.

 

An integral part of stringing open wire was the cutting in of transposition elements into the lead. Here is a dramatic image of Gene Grey, a Southwestern Bell employee, using a block and tackle to do just that. Photo credit: Russ Clayton.

An Article Published in 1952 on J-Carrier Additions to the Salt Lake, Utah-Helena, MT AT&T Long Lines Route

This article was originally published in the Lines West newsletter in late 1952 (don’t have the information to cite a specific date) which dedicated an article to the re-construction of the Salt Lake City, UT to Helena, MT J-Carrier Long Lines toll lead.  Thank you Bob Tally for making this available to Song of the Open Wire.

 

I would like to give more credit here, but the article was torn out of a journal and then copied for “Song’s” use here.  I am publishing this long lost article in the spirit of research purposes only and hope someone can furnish more specific information about its citation.  We would be more than happy to be furnished an attribution as far as photos and captions are concerned to credit them.

 

Meanwhile, this is a great example of open wire stringing activity in the immediate post-war period where 12-channel carrier was yet being used.  O-Carrier would be introduced in 1955.  I greatly appreciate the individual who sent this very interesting glimpse of aerial wire stringing activity from his scrapbook of working with the Long Lines Department of AT&T.  He is one of the people involved (and pictured) below in the re-building of this particular lead.

“Western Area Linemen String & Transpose Wire in Utah & Idaho” c. 1952

Tools of the Stringing Trade

Have a trailer?  You’ll need one!  Not even a long trailer, just something to allow the stringing reels to be anchored and the wire to be payed out from behind.

Open wire stringing was done differently in each case, because it depended upon the modesty or ambitious nature of the job.  For construction of a little service station line to a farm, with two conductors placed with two wooden brackets not much more than ten feet above the ground, it was a simple affair.  Spans tended to be rather long, but the weight of a mere two wires did not greatly stress the structures.  Also, the line wire could be pulled from two stationary reels mounted on the ground or trailed behind a truck.

If you strung more than two conductors, four or more, then it was important to have one critical construction asset: the moving multi-reel set-up.  It’s utility was quite clear for these reasons:

a moving reel trailer could pay out the linewire gradually instead of being limited to two wires with a stationary reel.  Why not reduce your work instead of having pulled a single line wire out of the reel?

secondly, with this set-up, you could easily pay out up to ten wires at a time without unequal stress on each line wire as it is hoisted to the arm.

Thirdly, in the case of later aluminum and copper covered conductor, it was extremely important to avoid scratching or abusing the 1000th of an inch annealed bi-metalic surface, which would cause resistance issues later in operation.

If you were performing this kind of work professionally, and continually, at an I&M facility or as a line construction contractor, it was essential to invest a little more in order to purchase a Wire Reel Brake unit.  What was fundamental to its use was that you could have automatic braking without uncontrolled releases of wire as it was payed out.   Everybody can remember pulling hose or wire from a reel and having it uncontrollably spin releasing a tangle of material on the ground.

The genius of such a device, was the brake unit with an adjusting screw.  This screw might easily be set by the user when first using a spring balance tool to determine your lbs. of pull and then setting the screw to, let’s say, 30 to 40 pounds of exerted force, so to freely exert line wire from the reels. There was a brake lever arm on the device, which was not intended for inserting line wire–which to the novice was a common mistake; instead, the brake shoe adjustment was made and the line wire would be placed into an eye of the adjoining lever arm.  Then you would have command and control over the braking action as the wire was released.

The fastest operation of paying out line wire was done at around 5 mph. or less, so that the line conductors would equalize stress throughout the job.

Now, I bet you’re asking?  What if you’re in the mountains or swamps where this kind of process might be . . . challenging?  Yes, I’m going to get into that issue later, but since we’re going to explore the basics of this task, let’s just assume we have nearly level, slightly hilly, but accessible ground, with easements near highways or rural roads.

For small jobs, such as the example with the little rural service station wooden bracket lead, we probably wouldn’t need the larger trailer.  It could be accomplished with two reels in the back of a small truck and a tree pruner hot-stick, and the hard work of two men.  The tree pruner could have its universal head accomodate a wire raising tool insert.

The number of wires which were to be strung dictated the size of the wire reel brake device limits.  You could pay out as many as ten wires on a single trailer.  While a two-wire stringing job allowed line wires to be casually dropped in the bar ditch and then hoisted to the wooden brackets or REA sidearm, things got complicated for larger jobs.  

So let’s introduce another essential tool of the line construction forces for multiple line wires: the Transposition Running Board.  Along with the standard number of fiber ropes and snubs, and a good knowledge of knot tying, it was essential to pulling in at equal stress, the four wires of two pairs to each arm along the length of each stage of the project.

Transposition Running Boards were limited to four wires–a phantom group–so if you had a ten-wire line, you’d need two of these on separate lead ropes placed on either side of the pole center sides. The pole pairs would be handled separately.

Methodology for Stringing on Phantom, Drop and Tandem Bracket Leads

With your specifications and drawings in hand, which covered in measurements and meticulous detail the various on-going features of the line’s route, you could begin your stringing project.  Being appraised of where the transpositions to be cut in, special feature issues, such as obstructions, trees, overhead power distribution lines, longer span desigs over rivers, highways, rail lines and so forth, allowed you to carefully begin the stringing aspect of your job.

A single stringing job could only be as long as the wire lengths on the reels.  For example, for 104 copper conductor, the standard coil maximum length in feet is 4,660.  Sounds good, right?  Now, try to pick this up . . . that’s 90 lbs. slung under your arm.  What if you’re stringing four or ten of these?  Just multiply and you quickly ascertain the load limit of your stringing device and trailer vs. the weight of all that wire.  And this 104 copper is nothing compared to a toll lead requirement where conductors of 165-mil copper were applied.  In this latter example, you were limited to only 2310 feet and a standardsingle coil of this weighed 190 pounds!

When the wire was unloaded, it was essential that it be protected from abuse; not to be nicked, twisted, bent, scratched prior to installation.  If these defects were found, then it was essential that these faults be cut out of the line wire and be properly re-joined.

Important aspects of planning an open wire stringing job boiled down to these:

How big was your job?  Was this a two mile exchange line with ten wires?  Or a forty-wire toll lead and aerial cable underslung beneath?

What kind of equipment was designated for this job?  What equipment was allocated from the installation people in order to perform this task?  Would it have allowed completion of the project in the time scheduled?  Would this equipment meet your project’s aims? 

What were the job conditions on-site?

Here were some other important criteria to consider when considering the size of your stringing job:

How big was this project in terms of manpower?  Was this a small job requiring two or three individuals?  Or a big stringing job with ten?

If this was a large job, would it consume considerable manpower and large allocations of equipment?

And think about this:  what was the maximum amount of wire which could be released from this reel brake device at a time?  Metal wire, which has considerable weight at rest, not to mention as it achieved momentum, would exert significant force.  The machine was limited to a safe controlling weight limit.   In one pull, there was a maximum amount of wire to be released, plus the number of wires which were to be strung.  Add all of this to the fact that few lines, even on the flat plains, had tangent geometry throughout their entire length.  There were corners of varying angles, special line features over creeks and highways, as well as the uneven nature of phantom transposition twists and attachment to a multiplicity of drop and phantom brackets. 

There was aspect of where to . . . start . . . the job!  Do you start at one end of the line under construction?  Do you start in the middle and go in opposing directions?  Do you string two wires the entire length and then add the other two on the opposing side of the arm during another performance?  All of these considerations were important when reviewing the construction needs of an open wire stringing job.

We’re going to use our less complex, nearly featureless, Great Plains model for this construction problem.  In our example, we have set up our equipment out of the way of traffic, so as not to pose a danger, or at minimum–a nuisance–to travelers. The reel trailers must be located outside of the shoulders of highways, nearest the fence line or bar ditch, so as to be in proximity to the poles and supports where the line easement is located.

The plans would specify pin positions these new wires would soon occupy for each pairs and circuits.  The telephone plant transmission engineers prioritized on plans the importance of each circuit.  In doing so, these plans would have indicated what pin positions were required to be “toll” and which are to be “exchange,” should they be jointly installed on the same pole line.  This was extremely important in regards to transpositioning and wire guages selected for conductor each.

Toll circuits were most important circuits and would have occupied the uppermost arms of any lead.  Naturally, these were usually the longest in length.  All principal high quality circuit classes were on the upper arms.  If the lead had both toll and exchange circuits, as did many of the transcontinental leads nearest suburbs and towns along their path, the rule was:

Never string the less important exchange circuits

on toll crossarms unless there were instructions otherwise.

Once the pair of wires was payed out, these wires had to occupy the same pin positions for the entire length of the job.  Cutting in transpositions would be done later; the critical aspect was getting the line wire into the air and having each line wire coordinated to proper pin locations.

On a large job with twenty or more wires to be strung, the line stringing would be broken into stages.  Stage One might be the beginning of the line at the terminal structure or junction structure with another lead.  At the estimated location of the line wire reel limit, another trailer with fully loaded reels would be set up to begin from that point, to which the ends would be spliced and joined together.  At a third location, another pay out reel brake trailer might be located to do the same as the second and so forth, depending on the full length of the project.

It was important to have sufficient rope to enlist for diverting tension by installing “temporary” rope head guys.

Having a guy in charge who signalled to others on the team, visible at all times, was imperative so that guidance could be given or in emergencies, when it was necessary to stop the pull suddenly. 

Wires were to be placed by a Pulling Line which was in turn, attached to the horizontally snug Transposition Running Board. Here the Pulling Line was carried over the top of each crossarm, nearest the pole/arm center.   Attached to the guide rope was a single metal snap from which dropped a secure rope for the groundsman.  This rope was called the Guide Rope, for which manipulating the transposition running boards to the equal distance necessary to divide the multiple wires and guide them into the proper pin positions, was necessary.  At about four feet from the Board’s placement beyond the crossarm, the line wires would be fanned out and the board dragged to the next pole and arm in turn.

If transpositions, such as phantoms were to be placed, the Transposition Running Board was manipulated to turn and twist a full 360 degrees so the proper pin positions on the bracket for the appropriate transposition type be secured.

At the end of the first section, a temporary head guy would be installed.  This temporary guy was usually a heavy rope tied from the top of the pole where the wire had run out to the base of the next pole where the stringing was to begin on stage two.

Now, the sagging began.  It was critcal to use the sag tables so snubbing the line wires at the end of the first section could complete stage one stringing.   Then the wires were tied in to the attachments (insulators) and subsequently snubbed again. This was done on each intervening pole between the beginning and end of the first section.

Continue this with the middle section and then with the final section (if there were three stringing stages).  The line wires were then spliced from each end point to the end points of the opposing section.

Methodology for Stringing Wire on Point-Type Transposition System Lines

The methods used for point-type transpositions stringing do not differ dramatically from those of the traditional stringing systems.  The major differences include no phantom groups, signficantly more attention given to the precise natures of sag and the introduction of consistently placed break-irons or point-type brackets.

How To Tension An Open Wire Line?

Tensioning aerial wire was important in the early voice frequency days mainly because of the properties of metal to shrink and expand with temperatures, inflicting considerable stress on attachment points.

 

When high frequency carrier was introduced, further necessities for re-examining the sag art arose.  This was critical in building new lines after 1938, when Type “J” Carrier and similar comparable 12-channel technologies became a part of long distance service.

 

A sag is defined as the distance between the wire’s top most attachment point and its meeting point at the lowest point of the arc of that line’s travel.  Sags do not have to be placed on level ground.  They occur on sloping, or on grade, between curves and at terminations. 

 

Sags in the early days were done by sight; that is using a Sag Guage or Sag Template, to achieve a satisfactory consistency between the many poles of a lead throughout its length.  Any induced physical stress imbalances would lead to wire fatigue, weakening of poles and other supports, such as crossarms, braces and brackets, and these imbalances would need to be corrected by sag sighting or by the introduction of corrective measures, such as guying and anchoring.

 

This is how it was done by sighting method:

 

Take a measurement of the span from the center of one pole to the center of the next pole and use the nearest value inthe sag tables which would then be your span length.

Using the tables, read the ambient air temperature with a thermometer.  At the temperature column on the sag table, match that to the sag length.  Take your hand and grab the line wire within the span desiring to be corrected.  Let loose slightly.  Take a span length as an example around  9-10 spans away. 

By using the Sag Guage or Sag Template, hang the device on the crossarm at the upper hook.   You’ll need two of these devices.  One placed at one pole’s crossarm of the same span (same comparable arm, of course) and one hooked to the crossarm of the other pole in the span.

At the bottom of this tool, you will find a broad target which can be seen without difficulty on both tools and is adjustable with wing nut attachments.

Set the target on each guage so that the top coincides with the figures corresponding to the amount of sag specified for the particular length of span and temperature.  

Sight across from the top of one target to the top of the other and withthe wire resting on the top of the crossarms, adjust the sag inthe wire by pulling up or slacking back, until the lowest point in the span is in line with the tops of the targets.

Do this with the next span and so forth; if you have special instances of line wire geometry, such as angle and ninety degree dead-ends, some further adjustment will be required.

Here’s how it was done by the oscillation method:

This method can be used for both sag and tension.  The wire is pulled and then dropped by the lineman.  Within 15 seconds, a record of the number of oscilations, or vibrations, is counted.  The sag is indicated by the number of oscilations during that brief timed period.

All wires on a transposition running board should be pulled up with equal tension.  This method insures this, as each wire of the four, is pulled, snugged and dropped with a count made as to the proper sag.

The span to be used for test should be an “average,” not special condition span.  Crossarms, pin locations, should be identical, just as in the sighting method.

The wire must be free from interference, such as a tree limb, roof of a house, chimney, other power or telephone pole.

This method dictates that the first span to be tested is from the terminal structure advancing to the final end structure, i.e. advance towards the pulling end of the line.

If the line is flat and consistent, it was not always necessary to check every span; in fact some checks were done every ten spans or so.

After the test span was selected, use the sag tables to match the proper combination of sag inches vs. no of oscillations over 15 seconds.

Before the oscillating of the span was done, the lineman would signal before pulling the wires taunt.  The lineman was then able to do several tests to find consistency in the measurements.

Sometimes, despite considerable effort, the lineman was only able get the line to oscillate mildly.  The foreman would then signal and insist he move the line wire sideways to see if that made a difference.  Numbers of oscillations were then counted by the lineman on the pole, holding the wire on the insulator with the left hand and holding a finger on the right hand near the wire at the crossarm and counting the number of times within fifteen seconds that the wire hits the finger.  This is the nubmer of oscillations of the wire which would correspond to those selected from the table.  If the wire oscillations were less than required, the wire would be made further taunt; if more oscillations were present, then some slack would be introduced into the conductor. 

It was recommended by installers and linemen I knew, that the method was advised to be done several times–not just once.

And you ask? What if new wire is being strung on a ten pin arm which was only carrying four existing lines below that of a cable or other aerial wire?  What do you do then?  This happened frequently.  Typically, the sighting device took pre-eminence as the sag of the new wire had to be equal to the existing wire sag, so as not to introduce excessive tension on one side of the pole or arm.  Also, it was frequently the case where poles had warped, anchors and guys had brought a line out of its regular lead geometry, to which the lineman introducing new wire had to impose new thinking.  It was important to determine whether existing wire was suffering fatigue from this relapse in line design and whether these conditions needed to be corrected before stringing new wire.