Give Me A Fulcrum

Day 132: "Give me a lever long enough and a fulcrum on which to place it and I shall move the world" (or as I learned it as a child, "Give me a fulcrum and I will move the Earth"). Archimedes was speaking in reference to the simplest of mechanical devices, a beam of some sort which pivots on a fixed point. And that is all you need to know about the operation of a loom.

Okay, maybe that's a slight exaggeration. The mechanics of loom construction actually involves compound levers, i.e., those which operate other levers which may in turn operate yet another set of levers. In a rising-shed loom, a treadle (foot pedal) is depressed, pulling down on one end of a jack (B), causing the opposite end (C, raised) to lift. The jack raises a frame (harness) holding a series of heddles (E). The tops of the metal bars on which the heddles are mounted in the harness is shown in (D). This creates a triangular gap between two layers of threads (the shed). The shuttle bearing the weft thread passes through the shed, the treadle is released to lower the jack, and the harness resumes its resting position. More than one harness can be raised at once or, depending on the tie-up (the way the treadles are attached to the jacks), a single treadle may operate a pair of harnesses. Unwoven warp is supplied from the back beam (A), and the finished fabric is wound onto the cloth beam (F), both of which are operated by yet another type of lever, the ratchet. Leverage. Pretty simple when you think about it.