Is it the red or the blue wire? Careful, if you cut the wrong one your ashy remains will be found after the dust settles from a mushroom cloud explosion…
Greetings, geeks! I haven’t posted in a while so figured I would. I’ve had safety wire on my mind lately so I decided to search the Interwebs for anything that would serve as a quick guide or at least a refresher. What I found was a nice short video from SpaceTEC:
“Safety wiring is considered a redundant means of securing components to prevent them from becoming loose, should the primary retention capability fail during operation.” That is what the first screen of the video says. ‘Redundant’ used in this context does not mean something negative; SpaceTEC is not talking about overusing words in a five-page paper in English class. Here, redundant simply refers to the purpose of safety wiring; it acts as an additional and precautionary measure so that parts, most often hardware, remain intact. When it comes to securing fasteners (nuts, bolt, screws, etc.) and preventing vibrational forces from loosening parts, safety wire is a reliable and inexpensive means that leads to peace of mind.
The next screen from the above video states: “Items shall be safety wired in such a configuration that the safety wire shall be put in tension when the parts tend to loosen.” The screen displays two images—illustrations of a safety wire installed on bolt-heads and safety wire used on Castle nuts. This serves as a nice visual aid to give you an idea of the appearance of the configuration. Such a configuration allows for the safety wire to act as an antagonist to the part, meaning as the nut loosens, the wire tenses up. It is similar to how muscles function: as one muscle expands or extends, a corresponding muscle contracts. Imagine if both muscles contracted at the same time? Snap! Well, if a safety wire loosens while a part loosens, it defeats the whole purpose of the configuration.
The third screen retains the two images from the previous screen. But now Aircraft Circular AC 43.13-1B is mentioned. “AC 43.13-1B covers all the aspects of general safety wire practices. There are three common sizes: 0.020, 0.032, 0.041. New safety wire shall be used for each application.” Check out Pages 19-25 of the Aircraft Circular AC43.13-1B where the FAA provides guidelines for “safetying.”
For the fourth and final screen of the video, safety wire pliers are briefly touched upon, particularly how they should be used to apply the wire: “Safety wire should be twisted six to eight turns per inch. The pigtail S/B 1/4 to 1/2-inch (three to six twists).” A picture illustrates this point.
For those who don’t know, SpaceTEC —located in Cape Canaveral, Florida— is the National Science Foundation’s (NSF) Resource Center. Its primary mission is to serve as an advocate for employing aerospace technicians. The organization achieves this by providing an academic outlet for such individuals. This leads to a well-trained workforce for commercial, civil, and defense space activities relating to the aerospace and aviation communities.
According to SpaceTEC: “Its certification programs offer performance-based examinations that result in industry-driven nationally recognized credentials that reflect the competencies employers demand. The certification program is offered through a nation-wide consortium of community and technical colleges, universities, business and industry organizations, and government agencies.”
The good news is that SpaceTEC recently received a grant renewal from the NSF; this was accomplished through the NSF’s Advanced Technical Education (ATE) program. This will certainly help with further developing the certificate program, which consists of five key areas – Applied Mechanics, Basic Electricity, Industrial Safety, Materials & Processes, and Tests & Measurements.
Thanks to SpaceTEC for offering a quick reference for the applied mechanics of safety wire.