Western Union splice
This article needs attention from an expert in Electrical engineering. The specific problem is: question has been raised about the graphic, particularly the ways that the left vs. right twists are shown in final splice versions in critical figure parts D, E, and F.August 2019)(
The factual accuracy of parts of this article (those related to the description of making the splice, etc.) may be compromised due to out-of-date information. In particular: splice-making is from a very dated source, and that and current significance in electrical work need updating; as well, accuracy of the graphic images from this source have been questioned. (August 2019)
The Western Union splice or Lineman splice was developed during the introduction of the telegraph to mechanically and electrically connect wires that were subject to loading stress. The wrapping pattern is designed to cause the termination to tighten as the conductors pull against each other. This type of splice is more suited to solid, rather than stranded conductors. In 1915, it was described as being, "by far the most widely used splice" in practical electrical wiring work.
The Western Union splice is described as having two variations, the "short tie" (figure part D) and "long tie" (figure parts E or F), with the latter examples having a "twist between wrappings [that] allows a better chance for solder to pass in between the wires" (as stated in a 1915 practical textbook), and so the long tie variant was seen as more suited to splices where soldering was intended. However, when examined in tensile strength ("pull") tests by NASA on 16 and 22 AW gauge wire, even the short tie variation of the Western Union splice performed well after soldering: when spliced and soldered carefully to standard instructions, the test splices never failed at the splice (instead breaking outside of the splice area), leaving NASA to conclude that "the solder connection at the splice was as strong or stronger than the un-spliced wires."
A 1915 textbook description of the short tie Western Union splice has it being formed after stripping the insulation from a pair of wires for 3 inches, each, crossing the wires left over right as shown in figure part A; then, a hooked cross (figure part B) is formed holding the crossing point of the two wires, and pulling the right wire tip toward and pushing the left wire tip away from the worker, leaving the tips oriented vertically as shown. The wires are then held with pliers to the left of their crossing point while the right splice is formed by continuing to wind the wire tip away from the worker, creating 5-6 twists snug against the core wire and against each preceding twist, that is, "tight, with no gaps between adjacent turns." The wires are then again held with pliers, but on the first-made twist, to the right of the crossing point, and then the left splice is formed by winding the remaining wire tip toward the worker for a comparable 5-6 snug twists. The splice wire ends are then trimmed as needed, and the splice may then be soldered, and/or covered (e.g., with a heat-shrunk tube of insulation).
- Sharp, John MacLaren (1915). Practical Electric Wiring. New York and London: D. Appleton and Company. pp. 13–14.
- "Western Union/Lineman Splice". NASA Workmanship Technical Committee. Archived from the original on August 1, 2009.
- The NASA tests included soldering, and were performed to an organizational standard operating procedure, NASA-STD-8739.3, for a solder termination, which includes a number of specific requirements, including "proper insulation spacing", the tight wrapping described in following in the main text, trimming of wire ends to prevent protrusions through the solder, and over-sleeving with a transparent or translucent heat shrink seal to cover the completed splice and all exposed metal. See the preceding reference.