utility pole question

Thu Aug 10 10:03:35 EDT 2023

Abe, I’m not von Rector, but I want to (again) thank you and others for sharing this kind of information and these deep dives. I didn’t know I had an interest in pole lines (beyond a ROW element) - until you showed the entrance to the rabbit hole…

I once had a conversation with a utility line design engineer at a social event, and found the information on material usage for towers vs. weight of conductors and their carrier lines vs. span quite interesting. You don’t know what you don’t know - until you ask.

Matt Goodman
Columbus, Ohio, US

> On Aug 9, 2023, at 11:14 AM, NW Mailing List <nw-mailing-list at nwhs.org> wrote:
> 
>  
> Herr von Rektor, Excellency:
>  
> I have gone through a lot of material on early Pole Line construction, beginning in the earliest time when wires came to be put on poles in America (late 1843.)  
>  
> Here is a tip:  Try searching for "pole line" rather than "utility pole."  "Pole Line" was the railroad's nomenclature for such construction.  In the world of pole-dudes, a "utility" pole  connotes something which carries the wires of a public utility such as telephone or commercially sold electric power.
>  
> The very earliest telegraph poles were 30 and 32 feet in length, and that was not tall enough.  Most railroad construction records I have seen from the  mid-19th Century called for 35 foot poles, spaced 33 to the mile, with those numbers adjusted according to requirements of the geography.  Back in the day before wood preservation chemistry, Chestnut was the preferred wood as it has superior resistance characteristics to deterioration from moisture.  Most railroads (as well as Western Union and AT&T) called for 4 feet to be buried in the ground.  Where additional stability was required, guying was preferred to burying more of the pole in the ground.  Additional stability means the necessities caused by curvature, terrain crossed, grade (slope) traversed, weight of wire to be carried, wire sag required between poles due to pole spacing, anticipated "loading" due to ice, snow and high winds, the amount of under-wire clearance required for crossing streets. waterways  and other railroads, etc.  The bracing of cross-arms  (so that they did not flop on the pole) was also engineered.  Once cable was introduced, that added tremendous weight loads to pole line, as early cable was Lead-sheathed - there were no plastic insulations in those days.  Here at Harrisburg, the railroad still had into the 1990s,  circuits operating in Lead-sheathed cable (both aerial and buried) which had been in service since the 1930s.
>  
> Early pole lines did not use cross-arms.  Rather, they used "pole brackets" (slanted wooden stand-offs nailed to the pole and having a glass insulator at the upper end.)   As more wires were added, cross arms came into use.  The earliest cross-arms accommodated two or four insulators mounting pins.  Eventually the 8-pin and the 10-pin cross-arm came into use, and I have seen photos of giant 12-pin arms.  The early glass insulators were un-threaded and popping off the supporting pins was a major problem.  The internal threading of glass insulators was patented by a man named Louis A. Cauvet in 1865, and the earliest threaded insulators were made at the Bushwick Glass Works in Brooklyn, NY, and were marked "Brookfield."  Brookfield made most of the early railroad insulators and ceased production in 1923, after which Hemingray of Muncy, Ind., the Kerr Glass Co. and Armstrong continued  production until 1975.
>  
> Of course, due to its preeminent place in early communications history, Western Union (an 1857 merger of earlier companies) worked out all the best engineering for pole line construction, and had its own manuals... WU even its own railroad cars!  Later AT&T entered the wire business and had its own (very similar standards.)  It appears to me that most railroads, rather than re-inventing the wheel, just adopted the best pole line practices as worked out by the WU and AT&T engineers, with perhaps a dash of the railroad's Chief Engineer's idiosyncratic druthers thrown in for good measure.  You might get lucky and find a sheet or two of N&W pole line specs in the N&W M-of-W Standard Plans (which I do not have.)
>  
> Height of poles was always and everywhere a function of how much under-wire clearance was needed + how many arms the pole line carried + pole spacing.
>  
> I have amassed a good deal of early (beginning in the 1840s) material on this subject, if you want it.  Right now I am looking at Specifications for the Construction of Railroad Pole Lines, by Communications and Signal section of the Association of American Railroads, editions of 1924, 1939, 1950, and 1963 (the last edition.)  These volumes are about 300 pages each.  You may be able to get them on Google Books.  If you want anything particular looked up, let me know.
>  
> This AAR book of standards lists specification for erecting poles of the following lengths in feet:  18, 20, 22, 25, 27, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85 and 90.  So you can see there was a lot variation provided for.
>  
> The N&W had been a member of the ARA/AAR since its beginning in the late 1880s, and had members who sat on the Train Rules, Signal, M/W Engineering and Mechanical (i.e. Rolling Stock) Committees.  So it is a pretty good guess that the N&W practices very closely followed AAR standard pole line recommendations.
>  
> In case you are scaling things off from a photograph, insulator spacing after, say, 1920 was 11 inches or 11  1/4 inches.  Cross arm lengths:  6-pin arm is 6 feet in length;  10-pin arm is 10 feet in length.
>  
> And, if I have not exceeded my alloted time, a few remarks on that wonderful photograph you provided of the 2163 at Boaz.  Top to Borrom:  (1)  Big 50"  support for the Static Wire, bent from 3" angle iron.  (2) A "Tramp (transposition) Bracket" carrying a three-wire circuit.  My guess is this is some form of 3-phase 220 or 440 volt AC power to feed the AC track circuits and relays the N&W used on the Norfolk Division.    (3) The upper cross arm, made for 10-pins.  My guess is this carries signal circuits.  (4) The lower cross arm, made for 10-pins.  Notice the outer pairs on either end are "tramped" (transpositioned) so one is definitely the Train Dispatcher's telephone wire; the other may be for wayside phone line or a multiplexed Carrier circuit.  No guess about what the other four insulators may carry:  perhaps single-line Morse Telegraph circuits or Teletype circuits.
>  
> I have a LOT of history material on pole line, insulators, wires, circuits, etc, dating back to the 1840s.  Let me know what you need.
>  
> -- abram burnett
> Supervised Crossover Extracellular Matrix Isocaloric Turnips  :-)
>  
>  
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