Canadian Pacific Railway communications department catenary span as creatively portrayed by Erik Boucher.
Anchors, Guys and Catanary Spans
Photo above taken by Arend Gregor, Calgary, Alberta, Canada, showing a typical catenary span over a gorge and the strand (messenger) supporting the 20 or so conductors. Utility was BC Telephone. Recorded image was taken during 1989 near Anarchist Pass.
An Introduction to Long Span Construction: Open Wire
My rationale for placing this commentary relative to catenary construction here results from the extension of guys and strands, which in aerial cable work, may support the complex geometry of suspended multi-pair compressed conductors. To take this engineering method, as applied to open wire supports further, the challenge of crossing long chasms, river crossings, canyons and demanding special terrain supports over multi-lane highways, encouraged its use.
I want to sincerely thank my correspondent from Canada, Arend Gregor, whose color photo of a rare installation (now deceased) in British Columbia presents a great example of this engineering standard.
The basic design of the open wire catenary for various telephone companies did not vary greatly. Indeed, the American Railway Association Communication leadership committee adopted the Bell standards and the idea did not incorporate any proprietary process as the laws of physics ruled over any patented elements of the design. So let me explain the design in the general sense, as it was adopted in North America by nearly all railroads and communications companies.
Criteria for Catenary Constructions
Let’s first refine the definition of “long span” as applied to open wire. Typically, these were atypical installations, being infrequently adopted where the average length of spans was challenged by a terrain feature. The length exceeds the average length of the five adjacent spans in each direction. As a structure, it too was confronted by climatological considerations, being where heavily loaded by ice, the minimum length would be 225 feet. In a medium load geographic area, the limit was 250 feet and finally, the lighter ice loading districts required a 325 foot minimum length.
The telephone companies, as mentioned in previous pages within this website, had a virtuoso of terms, similar, but not the same as the electric utilities, for example. You might turn Winston Churchill’s famous phrase on its head when applied to telcos and power organizations as, “Two English speaking engineering and construction organizations separated by a common language.” I think that fits nicely here. Where in power’s definition of terms, “messenger” is the same as “strand” in telephone parlance, for example. Again, the use of “fixture” by telcos differs from “frame” by the electric utilities. Get the idea?
Let’s discuss the two types of catenary “fixtures.” Telephone companies were fond of using “H-fixtures” in major toll leads as storm damage prevention when head guyed in both directions by four sets of guys. These sturdy structures had great transverse loading capability and in a major sleet storm, their intermittent placement over many miles of line prevented cascading failure of the lead. This had proved their value in tangent construction.
With this strength in mind, such “H-fixtures” were applied to either side of a gap or landscape feature to be crossed. They allowed the transfer of strain to both structures equally.
Sometimes, the telcos desired a more flexible double dead-end found in the “three pole fixture.” These two types were the only kind used by the telcos and railways.
This simplified diagram illustrates the profile of a typical catenary project. Illustration by D. G. Schema.
By dead-ending the catenary strands which were suspended across the gap by two equally strong two pole or three pole dead-ends, suspension fixtures could take the form of higher poles. These strands could then support the “hangers” which were connected to “crossarm support assemblies” (more on that later). The assemblies were then hung on a strand grounded and bonded to “riding” strand. This riding strand essentially gave further support to the crossarms and allowed the aerial portion of the structure to stabilize in the wind and maintain clearance of line wires.
Sometimes, the gap being traversed would be of such length that the dead-ending pole fixtures were not entirely sufficient to counterbalance the forces of gravity, load, weather or style of construction used. Then, the next “line” poles in the tangent approaching the H-fixtures or three pole fixtures would themselves be reinforced with additional head guys or extended guys.
Where the line wires (energized conductors) of the toll lead were placed beneath the various strand supports, they would be double dead-ended on c-brackets on either shore of the gap’s H-fixture or three pole fixture. Because of the strain, the dead-ending was necessary as the bouncing of the line wires, the expansion of the metal in the summer and contraction of metallic conductors in winter, made a “flow through” tangent line wire impossible.
I’ve drawn a couple of examples detailing the two types of structures which explain visually, the features of this unique project.
If you’ve ever looked closely at the high strength steel cable forming head, side guys or the supports for aerial cable, where it is lashed to support it to the strand, there must be enormous strength. Where the line conductors spanning the gap maintain the same diameter and gauge as the standard tangent toll lead character, the strands must be chosen from a variety of high strength steel alloy cables to meet critical weather loading restrictions relative to the site’s geographic location.
How many strands? Good question. As those strands and hangers supporting a suspension bridge with a roadway, train track or natural gas pipeline over a large gap, have to be selected with care, it is important to know the following information:
- How many crossarms and wires will this catenary support?
- What is the proper tension for the strand throughout the configuration?
- What is the wind, ice and climate characteristics of the location?
- Where are the hangers to be placed in the span?
- Is the span a “straight line”?
I have actually seen small catenary structures in Iowa near Blencoe, Mondamin, River Sioux and other locations along the original U. S. 75 north. This was the Sioux City-Council Bluffs toll lead carrying around five to six ten-pin arms on each pole. The Missouri River is close-by and the land is extremely flat. However, Soldier River, the Boyer River, were more than creeks, and at those locations, some small project catenary work was done (200′-300′). For mountainous regions, as our Canadian colleague pointed to in his great illustration above, the gaps were genuinely “challenging.” These presented major obstacles to line construction, including the fact that (unlike Iowa examples), granite prevented the boring of pole holes for the dead-end fixtures and other challenging arguments to their construction occurred
Illustration above portrays a typical four single tangent 10A crossarm hanger assembly. Note the placement of 30″ braces to stabilize the structure for wind control. The steel horizontal angles affixed to the top arm between pin numbers 2 and 3 and 8 and 9 (succeeded by similar second, third and fourth arm pin lower positions) offer dynamic strength to the entire assembly and maintain crossarm geometry as if it were a tangent pole supported structure. Similar to an alley arm assembly. Drawing by D. G. Schema
Okay. Enough about “gaps.” Let’s fill in some! For example, let’s say you have the same example as in Arend’s great photograph:
- Three (3) ten pin or W-8 crossarms with ten (10) or eight (8) conductors
- First crossarm assemblies (on either side) would be suspended 150′ immediately after the H-fixture
- Special steel angle iron crossarms (bolted to the tops of the crossarm fixtures)
- Special 2″x2″ galvanized steel angle
- 30″ span steel crossarm braces
- High poles (of Class 1 or 2 variety, towering approximately 50’+ in height) at each bank of the canyon (dynamited holes or bored in solid rock)
- Multiple double “head” guying on all dead-end structures
- Loading area: “Heavy” 225′ minimum length for long span construction (line wires)
- (We have to guess here) Approximately 1800′ gap between H-fixtures on either side.
- Total number of catenary suspension strands required: 2
- Six catenary suspension strands: 16M type strand diameter
- At 20-degrees F, Sag: 0-6″ with a tension of 4420 lbs.
- At 60-degrees F, Sag: 0-6″ with a tension of 3900 lbs.
- At 100-degrees F, Sag: 0-7″ with tension of 3560 lbs.
- Separation between catenary suspension strands and top crossarm at the H-fixture: 4′; Length of hangers: 8″
- Five (5) crossarm assemblies placed at approximately 150′-225′ apart
- Line wires crossing the gap must be in “straight line,” i.e. as the “ruling span” dictated so that there wouldn’t be a “dip” in the wires where the catenary crossed the gap.
Since we mentioned “sags” in the afforegoing data sheet, let’s dwell on that important element for a minute.
How many of you have heard of a Strand Dynamometer? Well some of you shook your heads and a couple nodded. A Strand Dynamometer is a device placed in series with the strand measuring the tension of the sag, and by applying the temperature taken at the time of stringing and reviewing a chart, one can devise the proper tension for the strand placed.
Line wire sags in the catenary suspension strands are measured by sighting in the usual way as is done for traditional tangent open wire construction. The tension for strand supports are measured with a Dynamometer. Both methods were usually applied while pulling the catenary suspension strands up to the proper tension. In making the final check before clamping the suspension strands, however, the strand dynamometer was used in cases where the sag is small and the tension high . Where the sag was great and the tension low, the sighting method was typically used. This was because the dynamometer method was the more accurate process where the strand tensions are high and the sags small; while the sighting method is the more accurate with large sags and low tensions. Got that? Let’s move on.
In the cases where two catenary suspension strands were dead-ended on one pole, one of the strands is dead-ended below the other. Where a long span is constructed without using a suspension fixture, the lower of the two suspension strands was installed first in accordance with the sag and tension information relative to temperature and climate. The upper suspension strand was installed so that it sagged down to a level with the lower strand at about mid-point of the long span.
Hang around . . . for more!
Let’s turn our discussion here to a few specifications and answer some questions related to catenaries in practice. I’ve illustrated a typical catenary dead-end two pole “H-fixture” and the hangers necessary to maintain the standard crossarm clearances and geometry of the line. You will note, with a few extra drilled holes and some special hardware, the crossarms are slightly modified, but standard dimensions for traditional open wire toll (or exchange).
Above are both single strand (top) and double strand (bottom) hangers for supporting ten-pin crossarm assemblies. American Railway Association, Communications Section standard.
What about transposition brackets and their placement when confronted with the special structures about to leap a canyon? The transposition scheme remains the same as the tangent, traditional line; e.g. break irons, drop brackets, 8″ or 4″ point type brackets, phantom brackets, are placed as specified on the outside plant engineering drawings, even though they may be in mid-span. Nothing changes. Of course, the I&M people might want the Transmission Engineers to specify aluminum Case span brackets or lighter weight break-irons, as required for weight relief on the span.
Numbering of poles. No change either. Here’s the rule followed by GTE, Bell and the Railroads (some exceptions): The numbering of the suspended fixtures was from one long span crossing fixture to the other. The suspended fixtures were evenly spaced across the span unless the detail plans stated otherwise. For example, a 600-foot span with three suspended fixtures would site the first suspended fixture spaced 150 feet from the crossing fixture and then the remaining two suspended fixtures located at 150 feet intervals.
A Great West Virginia Example
From the Association of American Railroads, September 1940.
Good Guys Always Win
Combination guyed structure utilizing a side guy in combination with a “sidewalk” style installation. Union Pacific Railroad, Rossville, KS 2013. Note lack of guy “guard” and insulator in series with strand to anchor for isolation. This was omitted because no energized conductors were layered below the operating communications wires.
Typical rural telephone down guy assembly.
Barely visible Chicago-Northwestern H-Fixture with double head guying, c. 1920.
Guy on joint use pole with double insulators for isolating signal circuit contact, Southern Pacific Railway. Note three-bolt clamps.
What kid hasn’t passed a power or utility pole of some kind or another and grabbed the guy strand and wiggled it vigorously, just to see and recognize that you were not powerless to make the untouchable facile to your whims?
Guys and anchors–besides the bases of poles themselves–are probably the most commonly familiar pole line hardware to the average citizen. Since the anchors and strands are generally not energized, they can be touched, bumped into, shaken (not red) and performs the ritual “straight ‘guy'” who trips a flag football player on his way to catch a ball fully caught as physical comedy on Youtube.
Two bolt guy clamp, 1920s to current.
However, guys, anchors and guards were not always the source of tripping a bumbling kid trying to catch a ball–they in fact, had a more serious intent: balancing the stress of unusual angled, dead-ended and geographically-challenged overhead utility facilities where unbalanced strain might inflict serious damage otherwise.
Guys are installed in situations where terminating wire occurs, terminating with follow-through circuits, junction and angle structures, 90-degree angles as well as hillside stress locations where a line is climbing or descending rugged or hilly geography.
Council Grove Telephone open wire angle structure with side guy to counterbalance pull as the line crossed K-177 north of Council Grove.
The Guy Next Door . . .
Double armed five degree angle structure on Transcontinental 1929 AT&T Long Lines structure in Nevada.
Guys are a necessary–and functional–part of open wire line design. They are typically overlooked by most telephone and insulator collectors, yet without them, securing a properly balanced aerial wire line and maintaining its strength under many different (and additional weather-related) loads would stop our basic communications and power infrastructure dead in its tracks.
Three bolt guy clamp, 1920s to current.
So, let’s take a look at some fundamentals of aerial wire and vicariously, self-supporting and strand-mounted multi-pair cable facility guying techniques, since they possess similar characteristics of load.
The guy is basically a balance support or bulwark against extraordinary stresses pronounced upon a structure, where a bending movement inflicts distortion upon th structure or line geometry. The world is not CAD-drafted, so as each open wire route fastidiously attended to the fence lines of roads and highways, natural curvature and junctions occurred very naturally. A number of guying techniques were introduced in order to build a rigidly conforming lead and to prevent unequal sags or a threat to the ground-level public.
There are several types of guys:
The most common are down guys and side guys. A modification of this craft is the “sidewalk guy” which is simply the application of a stay or extension in a regular “down” guy so that the angle of the guy strand will abruptly change to a directly descending strand so a sidewalk and pedestrians will not be impeded by a guy placed directly in the middle of the sidewalk.
The head guy might be employed in several unique ways. One is where limited easement is available and in order to supply strength to an approaching double armed railway crossing or long span highway leap, the guy might be attached near the top of one pole and then secured to the next pole (just six feet or more) above the pole preceeding it.
Extended guys used a pole stub, which was a great way to use good poles which had been pulled from previous duty elsewhere, but were too good to toss out at the pole yard (e.g. no rot, few defects, and physically strong enough to withstand secondary duty as a guy stub) and would manage to extend the strand from across a highway to an anchor placed on the opposite bar ditch ROW. This was traditionally done with tight easements where open wire lines were on the outside of a highway curve and directly placed side guys were impossible to place.
Three bolt “messenger” clamp for strand supporting lead aerial cable. From the 1920s. Note the differences between it and the three bolt guy clamp.
Storm guys were placed for the express purpose of preventing “cascading failure” of open wire facilities due to ice, sleet or unbalanced loads, such as a falling tree limb, washout or other notoriously common happenstance. Should the line experience cascading failure on one side of the storm structure, which was commonly typified as an “H-Fixture”–in telephone parlance, the guy placement was equally around it. That is, two side guys opposing one another on one side pole in parallel with the lead, the other two side guys placed parallel on the H-Fixture’s other pole and–if justified, dual installations of guys at 90-degree locations extending on each pole as well.
Guys which carried open wire and aerial communications cable were typically not insulated, that is, no separating links of cable were divided by a spacer insulator, commonly called a guy strain insulator. If the communications lead only carried low voltage telecom facilities, there was no need for this implement. However, when power secondaries, power distribution or transmission lines were carried on joint use poles or crossed communications wires, then it was necessary to prevent any live lines from delivering a knock-out blow to aerial phone lines should contact occur. By placing a strain insulator of the proper size and voltage rating (typically these were 5-kV, 9-kV, 15-kV, 25-kV or in series for higher voltage systems) one could prevent contact from proceeding down the guy to the anchor and possibly electrocuting some innocent kid or person below. The insulator allowed only the contact point guy strand between the pole attachment and the insulator to be live should such an incident occur.
To place a guy on an eligible open wire structure required measurement of two important factors: the a) lead and the b) height. The lead is the distance between the anchor and the pole (or structure) base; the height is the measurement between the anchor and the location where the guy is to be attached to perform the most usefulness.
While the calculation for determining size of guy wire at angles and dead-ends is basic, the situations are immeasurably different in each case–particularly when one considers that for the Rocky Mountains or in the Ozarks, rock may be the anchoring material rather than soil in Ohio or sand in Nevada. Choice of anchors is also a critical choice for the telephone plant engineer. More on anchors later . . .
According to the Lineman & Cableman’s Handbook, which is a remarkably good source through its many printings and editions for this topic, we can illustrate a situation where we need a side guy for some various line angles.
1. First we look at the breaking strength of the line conductor. If your open wire lead is carrying brackets, a single six pin arm, two 10-pin arms, or a line where the pole is slugging along carrying a 300-pair lead cable beneath its four outstretched and encumbered ten-pin arms, one must address the conductor (and/or strand/cable) breaking strength issue.
2. Secondly, one takes about half of the breaking strength as listed of conductor tables which would be normally under maximum loading conditions.
Edwin Kurtz gives a good example on Chapter/Page 12-9 of his 1955 edition of the Cableman’s Handbook:
Example: Line tension = 50% of breaking strength
For No. 2 Copper = 50% of 3,045 lbs.
= 1,522 lbs.
3. We “multiply the line tension by the constant corresponding to the angle in the line.” He uses a number 2 copper conductor for his electric distribution example at a 30-degree angle. So, if the “line angle in degrees is 30, then the angle constant is 0.517.” So further more, the number two copper for 30 degrees ends up being calculated by
1,522 X 0.517 = 787 lbs.
4. Kurtz takes the side pull of one conductor by the number of conductors in line to get the total side pull–which for open wire leads might be many multiple arms of heavy copper or steel conductor! Think of a 70-wire toll lead, for example! So, let’s say our line is carrying a comparative weight of three multi-pair cables so on that basis, we have 787 X 3 = 2,361 lbs!
5. Now, we look at a table provided for the outside plant engineer to find “the multiplying factor for the values, which in our example might be 1.41. Hence, when we “multiply the line side pull by 1.41 we have our answer; tension in the guy wire consists of: 2,361 X 1.41 = 3,305 lbs.
6. With Kurtz’ example, we are talking about equating power distribution physical loads with aerial communications plant–which in some cases, could be much more demanding than the power people would need to calculate.
A railway example, also typical of early Bell and others’ techniques, to suspend non-self-supportive lead cable along strand quipped with horseshoe rings. Note dual pole suspension clamp for strands.
Storm guying open wire.
Head guying a toll lead.
Note insulated guy on this Southern Pacific Railway structure in Arizona.
Early 1910 three bolt clamp design. A single and double bolt design was also available.
Attaching guys to poles and pole stubs.
To prevent slipping of strand, this is how you did it in the early days.
In the foreground is a strand with horseshoe rings for supporting lead cable. While this is a railway practice example, in the early days, commercial telephone used this technique widely in the field (both urban and suburban).
Ground bracing with half pole chunks.
1890s extended guy application example for open wire lines.
The guy is made up of a steel rope, or strand, selected for each application by the outside plant engineer from a variety of sizes to equal to the stress placed upon it at that particular situation. In telephone work, the strand–often called a messenger, in the parlance of the power distribution people–is not intended as a current carrying conductor. Naturally, it is true that all grounds are connected with the strand–or “bonded”–as the nomenclature goes, so as to defeat the damage inflicted by above power distribution/transmission short circuits or erant lightning discharges at guy points, but this is only a standard damage prevention measure.
In power distribution and transmission, the messenger will serve in Y-connected systems as the negative return conductor. In telephone cable and open wire construction, this is not the role of the strand.
Typically, the standard guy strand is composed of seven steel wires, each of a diameter of not more than .111 inch nor less than .107 inch. Each wire must be free from any imperfections and of a uniform diameter. Strand is drawn in a continuous length and cut at the site to perform its duty. The wires are twisted together in a lay, just as an aluminum or copper power cable is wound, but the lay must not exceed approximately 3 1/2 inches. In the early open wire days, the strand choices were pretty limited so a breaking strength of 6,000 lbs. was maximum design.
Rod eye for anchoring guys. Typical of 1926 to 1950s.
The idea of placing guys was not a new idea in the realm of pole line design, since Western Union, Overland Telegraph, Postal and other smaller companies had mastered the idea in a rudimentary fashion. However, as big toll leads were built from the 1880s onwards for telephone (and leased telegraph) purposes, the immense demands placed upon a single strand of galvanized wire looped around a short post with the strain of one or three side brackets, was exceeded, and the strand or steel cable design began to emerge for use.
Union Pacific Railroad H-Fixture double head guying technique according to the American Railway Association standard.
One good–and surviving–method of applying guys was fastening the guy strand around the pole numerous times, held in the early days by simple staples–later by special clamps suited for the purpose–and secured by a standard single bolt or three-bolt guy clamp.
In the early days before the specialized single- or three-bolt guy clamp, the steel wire was wound around the strand leading down towards the ground and then carefully “served” or artfully secured so that it would not release under tension.
Later a special “thimble eye” bolt was designed so that it could be inserted through a hole drilled through the pole and the strand threaded through (once) into the eyelet and then paralleled/secured through a guy clamp and then “served” a few inches beyond the clamp.
An early advertising illustration (1890) regarding installation of head guys.
1890s illustration of how to use a rock anchor system; note that the rod is almost at a 45 degree angle intersecting the strand. Below is a page from a 1926 Ohio Brass Catalogue with the steel wire thimble and guy rod available at that time. The thimble allowed the strand to seat properly without kinking of the guy strand and weakening it.
Guy stub with ground bracing
Extended guy with pole type anchor system, c. 1890s.
Guying single pole corners with two guys.
Guying single pole corners, another early example.
Guying two pole corners.
Another case of guying two poles as the lead rounds a 90-degree corner
Guying two poles as a lead makes a 15-20-degree curve.
Guys attached to anchored guy stubs.
“H-Fixture” on the old Southern Transcontinental Line taken in Arizona. Note that side guys are arrayed in parallel on either side of both poles to make it a “storm structure.” The other guys have been removed.
Head guying on H-Fixture, Union Pacific Railroad System, N. E. Kansas. Busy thoroughfare requires two H-Fixtures (reinforced storm structures) to protect vehicles, trains and pedestrians.
The tension in any guy wire always depends upon the distance between the anchor and the site of the pole. The more distance placed between the anchor and the pole determines greater resistance strength. However, in order to do this, the proper strand strength must compensate for this extended difference. When the “lead” is short, the amount of pull to equalize an unbalanced condition is much less; extending the height and lead must be taken into account.
Placing anchors in the early 20th Century
Anchors have evolved from the wrapping of a cut tree trunk tossed casually in a hole and tamped with earth, to sophisticated auger type devices placed and installed by heavy truck-borne machinery.
However, in the early days anchors were pretty rudimentary. Let’s examine types of anchors used in the telephone plant and how they functioned:
The Log Anchor, arguably the most traditional and oldest form of steadying guy locations where the cut log was not less than the length of a man and not any less wide than 8-9 inches in diameter. In order to restrain the log from twisting, a hole was drilled in a heavy plank, through which, a strand was threaded so that the iron rod was secure through the log and the tamped earth would maintain the anchor. The base of the log was required to be six feet minimum from the top surface and placed on a 45-degree angle. I’ve heard this anchor being associated with the moniker “deadman” anchor.
This is a typical rock-type anchor for guying, used around the early 1920s up until the ’50s.
Above is a 1926 Ohio Brass Catalogue with anchor types, including the Harpoon style, which is rather unusual.
Nevercreep Anchor, which began to be employed through the 1920s and early 1930s by telephone companies, was a major improvement. It too, was placed in a 45-degree configuration and was required to be six feet or more below the surface of the topsoil surface.
The Everstick Anchor which was another evolution with similar characteristics to the above anchor system but could be “augered” into the earth with a machine installed on a truck. The Nevercreep type required a hole to be dug where it was inserted and then filled and tamped with earth afterwards.
Both the Swamp and Rock Anchors were for specific climatological conditions encountered where bare earth was not present. The major difference in a swamp anchor was the introduction of extension links onto the rod or pipe so that firm depth could be established in deep marshes like the Everglades and coastal swamps. The rock anchor was a specialized mountain gear method of using a comparatively short rod–typically a threaded 5/8″ or 3/4″ or even 1″ rod with a nut on the end. The rock would be bored and then the rod inserted. Meanwhile, concrete would be poured into the hole, with the nut on the end securing the rod in one location while the tension pulled on the rod.
Guying single pole corners with a ten pin arm.
Single log type anchor example with open wire lead c. 1890
Screw type anchor typically installed with a motorized vehicle shaft.
Rock anchor in the World War I period.
The “Tree” Guy (and Anchor)
An early single strand light duty tree guy about 1900
The “tree guy” was a more common scene in the early years, but is completely out of favor today, as anchoring of guys to private owner’s arborary is in violation of numerous local laws and ordances. Yet, in the early years up until the 1940s, this means of securing aerial wire, power lines and other utility services pole line stability was seen frequently.
This particular picture is from an unknown source, but clearly shows the typical method by which such an installation of the 1890s-1930s might be afixed to a tree sufficient in strength to guarantee anchoring.
Attaching guys to trees, early 20th Century
Attaching strain plates to poles.
Connecting strand to guy insulators.
REA Specifications for Guy Assemblies
United Telephone (followed REA specs.) pole push brace near Decatur, Texas, 1998. Additional guying was required as line angle geometry crossed Burlington Northern Santa Fe railroad tracks.
With the gracious expanse of specifications available to us through my collection of REA open wire documentation, let’s review some of the unique characteristics of the design of anchors, strand and applications.
Because the strand (or messenger) was used for a multitude of reasons on aerial wire and cable, not simply guys and extended guys, we’re including some of the aspects of this steel cable.
Aerial cable in the early days was not “self supporting” which was an application seen much later, when it was possible to stretch the plastic sheath over the strand to make it integral to the cable. In the early days before “lashing,” cable was lead. Heavy as sin, and supported by “horseshoe” type clamps at varying intervals, depending upon the weight and outside diameter of the cable.
Because later open wire lines also carried aerial lead cable, the strand could be extended to other structures to allow for further bracing and providing substantial strength to the line as a whole. This is why we are including strand applications for not only guys and extended guys, but for cable applications, too.
Guy Strain Insulators
Guy strain insulators, as we’ve touched on briefly, are the best insurance against follow-through accidental electric power contact with guys and the ground in contact with them. The use of guy strain insulators has a rich and significant past, although not many people have become acquainted with them. These insulators were made glass and porcelain, wood, steel and iron (!) as well as fiberglass in more recent times.
While the guy strain insulator is commonly associated with “guy” wires, they naturally became utilitarian because of their versatile quality in dead-ending low voltage distribution circuits (below 9-kV) as well as be inserted into series street lighting circuits so that a jumper isolating the luminaire could be accomplished. The tough, rugged little porcelains available in many different glazes and styled according to the needs of their upper-end insulation values, were called “jonny balls” by lineworkers.
Telephone companies used the smallest of these for dead-ending farmer mutual circuit leads, occasional exchange lines. With some 109 steel line wire and a few twists, these utilitarian insulators found quite a following. Phone companies typically used only the lower voltage sizes–up to around 9-kV. Infrequently, there will be larger sizes found, but these heavier agents of insulation will be rare.
They also found their way into interruban trolly lines and allowed catenary systems to be secured with ease. I will select a few to be illustrated below and provide additional information at a later date.
Very early 1890s dry process porcelain strain insulator unknown manufacturer. 2-kV rating. Some utilities and many railroads used a steel or iron unit of the same design.
Green glass guy strain insulator for low voltage street lighting circuit jumpers
Detail of same insulator used by some telcos in the early days to dead-end open wire pairs. Unknown mfgr. Probably dated 1890s.
Wet process porcelain strain insulator. Unknown manufacturer. Note the date: 102 years old this year.
Another view of the above unit, rated 3-kV.
Victor disk-type guy strain insulator. This unit also did double duty as a break in series street lighting circuits. Rating: 5-kV.
Base of brown Disk-type wet process porcelain strain insulator which Iowa Public Service used extensively in the 1930s and ’40s.
Early 1920s PINCO 25-kV guy strain insulator.
Mid-1950s Porcelain Products 9-kV guy strain insulator
Typical application of the guy strain insulator to dead-ending signal power source circuit (2.4-kV UPRR). Disconnect switches have been inserted into this Delta two-phase lead to sectionalize it for maintenance.
15-kV ribbed style, possibly Locke/G. E. Ribbed outcoppings added extra insulating value to the unit. Clevis hardware, which allowed this unit to be used as a 15-kV dead-end, was also available.
Pinco red-brown 3-kV strain insulator from the 1940s.
Occasionally, a lineworker would be minus the guy strain insulator so inserting a secondary spool insulator in series with the guy worked, too. Joslyn secondary spool from the 1950s.