Notes, 2025-06-11

Some notes on rope, plus a few other tidbits, re: my recent essay on rope and progress studies:

• Here’s a video of some guys making a really heavy-looking sling out of a length of thick wire rope. The sling is maybe ten feet long and has eyes spliced on either end; if it were smaller then I’d call it a lanyard, but at this scale I’m not sure that’s appropriate. The eye is Flemished, meaning that its strands are separated into two parts and then wrapped in opposite directions around the loop; as the loop is formed, the strands are coiled back around each other such that the splice occurs in the loop itself. This has the advantage of not creating a bulged area outside of the loop (like the traditional ABOK #2725 eye splice does), though in the case of this particular sling I’m not sure if this is relevant.
  
  At the risk of romanticizing it too much, I love wire rope for the fact that it's almost always twisted, its twist geometry being much the same as ropes that humans have made from natural fibers for tens of thousands of years. It turns out that all twisted rope — whether it's made from hemp, nylon, or stainless steel — will perform best when it reaches the so-called "zero-twist point," when it becomes, for geometric reasons, impossible to twist its strands any further. This simplifies twisted rope-making, since all the maker needs to do to ensure good rope performance is to twist the rope's strands as far as possible.
• Twisted ropes can be formed with either a “Z” shape or an “S” shape, depending on which direction they’re twisted. Most three-strand rope is twisted in the “Z” shape. Take a piece of three-strand rope in your hand and orient it vertically, such that one end points away from you. You’ll probably see its twists moving up and to the right, like the middle part of the letter “Z”.
  
  Braided ropes are made from twisted strands — from an equal number of “Z-strands” and “S-strands.” The opposing nature of these two sets of strands results in a braided rope that is “balanced” or “torque-neutral,” meaning that it won’t twist when put under load. If your braided rope does twist for some reason — if you pay it out from a coil and put it into use immediately, without making sure it’s back in a neutral twist — then you may end up reducing its load capacity. Twisting a braided rope causes one set of its strands to be unloaded, and the other to be overloaded, as this technical bulletin describes.
• From the Cordage Institute, here’s a 44-page-long bibliography of cordage and cordage making. “Bibliography,” here, is used loosely: The first dozen pages read like a set of detailed but not-particularly-well-edited notes, and the balance is a list of mostly old, published materials, some containing information about their contents (“Some photos of old ropewalks,” “Mentions direct drive ropemakers wheel”), and some simply noted as “NOT SEEN.”
• Here’s a 19-page biography of Wallace Carothers, who invented nylon and then committed suicide shortly thereafter. And here’s a book-length biography, most of which is viewable in Google Books’ Preview scan.
• Tie a rope to something really heavy and lift it, holding the rope in your hands and letting the heavy thing swing slowly underneath you. The force pulling your hands down will be equal to the weight of the object. Then do the same thing with the rope looped over some kind of cylinder — a doorknob, or a pull-up bar, or the branch of a tree — and then back down to your hands. Now the force on your hand will be closer to horizontal (if you’re using a doorknob) or maybe pointing upwards (if you’re using a pull-up bar). This force will also, importantly, be much smaller than the weight of the object, as the friction between your rope and the capstan (the cylinder your rope is looped over) does some of the work of keeping the object from falling.
  
  This effect — the way that capstans reduce the amount of force you need to hold an elevated object on the end of a rope — is described by the Capstan equation, which was developed by Leonhard Euler and Johann Albert Eytelwein in the late eighteenth and early nineteenth centuries. According to the Capstan equation, the difference between the load force and the holding force is determined by the angle swept as the rope passes over your cylinder, and by the coefficient of friction between rope and cylinder. Take a couple of full turns around a cylinder, and you can hold a very heavy object with almost no effort.
• Here’s a short video, produced at a seemingly infinitesimal budget by the UK Parliament, about how the clock on Big Ben is maintained. Its pendulum oscillates every four seconds, and is adjusted by placing or removing pennies from the top of its pendulum.
• Here's a good, informative video about the rope bridge at Q’eswachaka, which was built centuries ago by the Inca Empire and is still rebuilt annually. The Incas also used knot tying to record history, creating documents called quipu that today represent "the only record we possess of this ancient empire."
• Zeppelins were invented by Ferdinand Von Zeppelin, a German general who resigned from the army in 1891 in order to devote himself full-time to airships.
• After watching a bunch of Mark Rober videos with my kids (who are eight and almost six), I’m considering giving them a subscription to his CrunchLabs boxes. If anyone out there has experience with the educational and/or entertainment value they offer, I’d love to hear about your experience.
  
  In related news, I'm solo parenting this week and am getting better at the roller coaster ride between "these are the moments I want to remember forever" and "I really, really need a break right now." On Monday and Tuesday we had school-related afternoon activities (notably, an extremely cute drama club performance), and managed to eat out at a neighborhood Indian restaurant (an extremely basic activity which I've been wanting to do with them for years). This afternoon I'm hoping to get them using hot glue guns (on rainbow-colored popsicle sticks and googly eyes), and tomorrow they'll hang out with their grandparents, and on Friday I'd like to get them soldering (a couple of old thru-hole project kits). Or maybe we'll spend an afternoon outside — maybe for a bike ride around Prospect Park, which the older one hasn't done for years and the younger one hasn't gotten around to yet.